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Winter Car Maintenance Myths: What’s Actually True?
Several popular winter car maintenance tips are outdated or wrong. Modern cars don't need a long warm-up, letting air out of your tires doesn't help in snow, and all-wheel drive doesn't help you stop. What does help in a Maryland winter: correct tire pressure, good tread, a tested battery, the right coolant, and rinsing road salt off the underside of the car. Quick answerMost modern cars need about 30 seconds to a minute of idling, then gentle driving. Idling for 10 minutes mostly wastes fuel.Tire pressure drops as it gets colder. Check it on cold mornings and fill to the number on the driver's door sticker.All-season tires handle light snow, but they lose grip in real cold and slush, especially when worn.Road salt and brine speed up rust. Rinsing the underside during winter is worth it.Never use plain water instead of coolant, and never pour hot water on a frozen windshield. Do you need to warm up your car before driving in winter? Myth: You should let the engine idle for 10 or 15 minutes on a cold morning before you drive. Fact: That advice comes from the days of carburetors. Most modern fuel-injected engines only need about 30 seconds to a minute of idling before you can drive off. The engine actually warms up faster when you drive gently for the first several minutes than when it sits idling. Long idling burns fuel and doesn't do the engine any favors. Your owner's manual may give specific guidance for your car. There is one good reason to wait longer: visibility. Clear all the snow and ice off the windshield, windows, mirrors, lights and roof, and give the defroster time to clear the glass. Driving with a small peephole scraped in the windshield is dangerous. And never warm up a car inside a closed or attached garage, because carbon monoxide builds up fast. Does cold weather really lower tire pressure? Myth: Letting some air out of your tires gives you better traction in snow. Fact: Underinflated tires hurt handling and braking, wear out faster and can overheat. On regular passenger cars, keep tires at the pressure listed on the sticker inside the driver's door jamb, not the maximum number printed on the tire. Cold air takes up less space, so tire pressure drops as temperatures fall. A common rule of thumb is about 1 PSI for every 10 degrees Fahrenheit. That's why the tire pressure warning light often pops on during the first cold snap of the season. Check pressure in the morning before you drive, when the tires are cold, and add air as needed. If the light stays on after the tires are filled correctly, or it flashes when you start the car and then stays lit, there may be a problem with a sensor or the system itself. That's something our TPMS tire pressure sensor service can check. Are all-season tires good enough for a Maryland winter? Myth: "All-season" means the tire is built for every winter condition. Fact: All-season tires are a compromise. They handle wet roads and light snow reasonably well, but the rubber gets stiffer as temperatures drop, and they don't grip ice or deep slush the way winter tires do. Winter tires use softer rubber and deeper tread patterns that stay grippy in the cold, and around 45 degrees Fahrenheit is the point often cited where they start to have an advantage. For a lot of drivers around Rockville and Montgomery County, where snow comes and goes, a good set of all-season tires with healthy tread works for most winter days. If you have to drive in every storm, commute early before roads are treated, or head to western Maryland in winter, winter tires or all-weather tires marked with the mountain and snowflake symbol are worth considering. Either way, tread depth matters most. Put a quarter upside down in the tread. If you can see the top of Washington's head, the tires are getting too worn for slush and snow. Myth: All-wheel drive or 4WD means you can drive normally on snow. Fact: AWD and 4WD help you get moving. They don't help you stop or turn. Braking and steering grip come from the tires, so slow down and leave more room no matter what you drive. Is it worth washing your car when the roads are salty? Myth: There's no point washing the car in winter because it'll just get dirty again. Fact: Maryland road crews use salt and brine to treat roads before and during storms. That salty spray coats the underside of your car, and salt speeds up rust on brake lines, fuel lines, exhaust parts, suspension components and the body. The paint is the least of it. The damage underneath is out of sight until something rusts through. Rinse the underside every so often during salty stretches, especially after a storm. Use a car wash with an underbody spray, or a hose if it's warm enough. Pick a day above freezing so doors, locks and seals don't freeze shut. Give the car a good wash when salt season ends in spring. Rust underneath shows up in the shop as corroded brake lines, rusted-out exhaust and muffler parts, and seized hardware. Keeping the salt off slows all of that down. What other winter car myths should you ignore? "My battery started fine yesterday, so it's fine." Batteries often fail without much warning, and cold weather is when a weak one gives out. Cold reduces the power a battery can deliver while making the engine harder to crank. If your battery is 3 years old or more, have it tested in the fall. Our guide to car battery care for Maryland winters covers testing, terminals and jump-starting. "Plain water in the radiator is fine." Water freezes, expands and can crack the radiator, hoses or even the engine block. Coolant, usually mixed about 50/50 with water, protects against freezing and corrosion. Use the type your owner's manual specifies, and never open the radiator cap on a hot engine. If you keep losing coolant, have the cooling system checked for leaks. "Hot water is the fastest way to clear a frozen windshield." Pouring hot water on cold glass can crack the windshield, especially if there's already a chip. Use the defroster, an ice scraper and a de-icer spray instead. "A half tank of gas is only about frozen fuel lines." Frozen gas lines are uncommon in modern gasoline cars. Keeping the tank at least half full is still a smart winter habit, though. If you get stuck in traffic during a storm or stranded on the side of the road, you'll have fuel to run the heater. Get your car ready before the first freezeWe test batteries, alternators and starters so your car starts on the coldest Maryland mornings.See battery and starter service QuestionsWinter car maintenance FAQ How long should I warm up my car in winter?For most modern cars, about 30 seconds to a minute is enough, then drive gently for the first several minutes. Take longer only if you need time to clear snow, ice and fog from the windows. Should I let air out of my tires for snow?No. Keep your tires at the pressure on the driver's door sticker. Underinflated tires handle and brake worse. Why does my tire pressure light come on when it's cold?Tire pressure drops as air gets colder, so a cold morning can push one or more tires below the warning point. Check and fill all four tires; if the light stays on, have the TPMS sensors checked. Do I need snow tires in Maryland?Many drivers in central Maryland get by with good all-season tires with plenty of tread. If you drive in every storm or travel to western Maryland in winter, winter or all-weather tires are worth considering. How often should I wash road salt off my car?There's no fixed rule, but rinsing the underside every week or two during salty stretches, and after big storms, is a good habit. Pick a day above freezing so doors and locks don't freeze. About the authorChristian owns New Level Auto Service in Rockville, MD. He has more than 20 years of experience working on cars and has run the shop for over 10 years. The shop is a licensed Maryland State Inspection station with ASE-certified mechanics who work on all makes and models. More about our shop. Bring your car to New Level Auto ServiceWe're at 716 E Gude Dr in Rockville, MD. Walk-ins are welcome, and calling ahead gets you in faster.Phone (301) 762-1200Hours Monday to Friday 8 AM to 5 PM, Saturday 9 AM to 2 PMExtras Night drop and 24-hour emergency towingCall nowDirections
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Vehicle Maintenance
Seasonal Car Maintenance Checklist for Maryland Drivers
Maryland weather is hard on cars in every season, which is why seasonal car maintenance pays off here. In spring, check for pothole and salt damage. Before summer, test the A/C and cooling system. In fall, test the battery and replace worn wipers and tires. In winter, watch tire pressure and rinse off road salt. Keep up with oil changes and brakes all year. Quick answerSpring: wash off salt, check alignment and suspension after pothole season, inspect tires.Summer: check the A/C and cooling system before the first heat wave.Fall: test the battery, check the heater and defroster, and replace worn wiper blades.Winter: check tire pressure on cold mornings, use freeze-rated washer fluid, and rinse the underside.All year: oil changes on schedule, brake checks, and don't ignore warning lights. What should you check on your car in spring? Spring is cleanup time. By March, most cars in Montgomery County have spent months driving through salt, brine and potholes. The goal is to find winter damage before it turns into a bigger repair. Wash the underside. Rinse off the salt that built up over the winter, including the wheel wells and under the car, not just the paint. Check for pothole damage. Signs include the car pulling to one side, a steering wheel that sits crooked when you drive straight, a new vibration, clunking over bumps, or a bulge on a tire sidewall. Look at the tires. Check tread depth and pressure, and rotate them if they're due. If you used winter tires, spring is the time to swap back. Replace wiper blades if they streak. Ice and scraping wear them out, and spring storms are a bad time to find out. If the car pulls, wanders or clunks after a winter of potholes, have the steering and suspension checked. A bent part or bad alignment also wears tires out early. How do you get your car ready for a Maryland summer? Maryland summers are hot and humid, and stop-and-go traffic on a 95-degree day is one of the hardest things you can ask of a cooling system. Get ready before the first heat wave, not during it. Test the A/C. If it's blowing weaker or warmer than last year, have it checked now. Low refrigerant usually means a leak, so topping it off without finding the leak is only a short-term fix. Our auto A/C repair page explains what we check. Check the cooling system. Look at the coolant level in the overflow tank when the engine is cold, and watch for leaks, a sweet smell, or a temperature gauge that climbs higher than normal. Hoses that are cracked, swollen or soft should be replaced. If anything looks off, have the cooling system inspected before a long trip. Keep an eye on tire pressure. Heat raises pressure, so check it in the morning when tires are cold and fill to the number on the driver's door sticker. Remember the battery. Summer heat wears batteries down, even though they often don't fail until winter. What should you do in the fall before winter? Fall is the most important season for maintenance in Maryland. Most of the problems that strand people in January can be caught in October or November. Test the battery. Most batteries last about 3 to 5 years. If yours is 3 or older, have it load tested before the first freeze. Our battery, alternator and starter service checks the whole starting and charging system. Check the heater and defroster. A defroster that can't clear the windshield is a safety problem, not just a comfort one. Check tread depth. Put a quarter upside down in the tread. If you can see the top of Washington's head, the tires are getting too worn for wet leaves, slush and snow. Replace wiper blades and switch washer fluid. Blades usually need replacing every 6 to 12 months, and summer heat bakes the rubber. Fill up with washer fluid rated for freezing temperatures. Check all the lights. It gets dark early after the time change, so replace any burned-out bulbs and clean hazy headlights. Check coolant strength. Coolant protects the engine from freezing as well as overheating. A shop can test how cold it's protected to. What car care matters most in winter? By the time winter arrives, most of the work should be done. Winter is about keeping an eye on things. Tire pressure. Pressure drops as temperatures fall, and the warning light often comes on during the first cold snap. Add air on cold mornings. If the light stays on after filling the tires, have the TPMS sensors checked. Salt. Rinse the underside of the car every so often during salty stretches, on a day above freezing, to slow down rust on brake lines and exhaust parts. Visibility. Keep washer fluid topped off and clear all snow and ice from the windows, lights and roof before you drive. An emergency kit. Keep a blanket, flashlight, phone charger, jumper cables, ice scraper, small shovel, water and snacks in the car. Fuel. Keep the tank at least half full so you can run the heater if you get stuck in traffic during a storm. What maintenance should you keep up with all year? Some maintenance doesn't follow the seasons. It follows the odometer and the calendar. Oil changes. Our general rule is every 5,000 miles or six months, whichever comes first, unless your owner's manual says otherwise. Brakes. Have them checked if you hear squealing or grinding, feel a pulsing pedal, or the car pulls when you stop. Tire rotation. Many manufacturers suggest every 5,000 to 7,500 miles, often at oil change time. Check your manual. Warning lights. A check engine light, battery light or temperature warning should be looked at soon, whatever the season. A note on inspections: Maryland does not require a yearly safety inspection. A Maryland State Inspection is required when a used car is sold, titled or transferred, such as when you buy a used car or bring a car in from another state. We're a licensed Maryland inspection station for Type A vehicles. Getting ready for winter?Fall is the best time to test your battery and charging system. Our ASE-certified mechanics check the battery, alternator and starter together.See battery and starter service QuestionsSeasonal car maintenance FAQ When should I get my car ready for winter in Maryland?October or November is a good time, before the first hard freeze. Test the battery, check tires and wipers, and make sure the heater and defroster work. When should I have my car's A/C checked?In spring, before the first real heat wave. If the air is weaker or warmer than last summer, there's likely a leak or a failing part. How often should I replace wiper blades?Usually every 6 to 12 months, or sooner if they streak, skip or chatter. Many drivers replace them in fall before winter weather. Does Maryland require a yearly car inspection?No. Maryland requires a safety inspection when a used car is sold, titled or transferred, not every year. Learn more on our Maryland State Inspection page. How do I know if a pothole damaged my car?Watch for the car pulling to one side, a crooked steering wheel, new vibrations, clunking over bumps, or a bulge on the tire. Any of those is worth having checked. About the authorChristian owns New Level Auto Service in Rockville, MD. He has more than 20 years of experience working on cars and has run the shop for over 10 years. The shop is a licensed Maryland State Inspection station with ASE-certified mechanics who work on all makes and models. More about our shop. Bring your car to New Level Auto ServiceWe're at 716 E Gude Dr in Rockville, MD. Walk-ins are welcome, and calling ahead gets you in faster.Phone (301) 762-1200Hours Monday to Friday 8 AM to 5 PM, Saturday 9 AM to 2 PMExtras Night drop and 24-hour emergency towingCall nowDirections
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Vehicle Maintenance
What Does a Car Diagnostic Test Tell You?
A car diagnostic test reads the trouble codes, freeze frame data, and live sensor readings stored in your car's computers. It tells a mechanic which system reported a problem and under what conditions, but a code alone rarely names the failed part. Finding the real cause takes hands-on testing, and that's the difference between a free code read and a diagnosis. Quick answerA scan reads trouble codes, pending codes, freeze frame data, live sensor data, and readiness monitors.A trouble code points to a symptom or a circuit, not necessarily a bad part.A real diagnosis adds tests that confirm the cause before any parts are replaced.Free code reads are a useful starting point, but they aren't a diagnosis.A scan can't see worn brake pads, tires, or most suspension parts. What does a car diagnostic scan actually read? Every car and light truck sold in the US since 1996 has an OBD-II port, usually under the dashboard near the driver's knees. A scan tool plugs in there and talks to the engine computer. A professional scan tool can also talk to other modules on most cars, such as the ABS, airbag, body, and climate control computers. Basic code readers usually only see engine codes. Here is what the scan pulls up: Stored codes: faults the computer has confirmed, usually the ones that turned on a warning light. Pending codes: faults the computer has seen once but hasn't confirmed yet. These can show up before any light comes on. Freeze frame data: a snapshot of speed, engine temperature, load, and other readings at the moment a code was set. Live data: real-time readings from sensors like the oxygen sensors, coolant temperature sensor, and mass airflow sensor, plus fuel trim and charging voltage. Readiness monitors: self-tests the car runs on its emissions systems. If they show "not ready," the codes were recently cleared or the battery was disconnected. Does a trouble code tell you which part to replace? Usually not. A code tells you what the computer saw, not why it happened. A few common examples: P0171 (system too lean): the engine is getting too much air or too little fuel. Causes include a vacuum leak, a dirty airflow sensor, a weak fuel pump, or a clogged injector. P0300 (random misfire): could be spark plugs, ignition coils, a vacuum leak, a fuel problem, or low compression. P0420 (catalyst efficiency below threshold): could be a worn catalytic converter, but an exhaust leak or a lazy oxygen sensor can set the same code. Replacing the part named in the code description without testing is how people end up buying parts they didn't need. An oxygen sensor code, for example, is often caused by an exhaust leak or a wiring problem, not the sensor itself. What happens during a real car diagnostic? A thorough diagnostic usually follows these steps: Confirm the complaint. Talk through what you noticed and when, and road test the car if needed. Scan every module. Read stored and pending codes in all the systems the car has, not just the engine. Review freeze frame and live data. See the conditions when the code set and how the sensors read right now. Run pinpoint tests. Depending on the code, that can mean a smoke test for vacuum and evaporative leaks, voltage and ground checks with a meter, a fuel pressure test, a compression test, or a battery and charging system test. Confirm the cause and explain it. Only then does it make sense to recommend a repair. Some problems are quick to find. Intermittent and electrical problems can take longer, because the fault has to be caught while it's happening. Free code read or full diagnosis: what's the difference? Many auto parts stores will read your engine codes for free. You get a code number, a short description, and often a suggested part. That's handy for knowing roughly where a problem is and whether it's urgent. A flashing check engine light, for example, means an active misfire and needs attention right away. A full computer diagnostic is different. It's a mechanic's time with professional equipment, testing until the actual cause is confirmed. It's usually a paid service because of that time, but it often saves money by fixing the right thing the first time. If your light is on, our check engine light page covers the most common causes. What can't a diagnostic scan tell you? The car's computers only monitor what they have sensors for. A scan can't tell you about: Brake pad and rotor wear Tire tread, alignment, or worn suspension and steering parts Belts, hoses, and most fluid leaks Many noises, rattles, and vibrations Faults that haven't happened often enough to set a code yet That's why a scan is one tool, not the whole checkup. Battery and charging problems are a good example: the scan may show low voltage, but a proper load test confirms whether the battery, alternator, or starter is at fault. The same goes for an ABS light, where the code narrows it down and testing the sensor and wiring finds the cause. Our ABS repair page covers that in more detail. Got a code, or a problem with no code?Our ASE-certified mechanics scan your car's computers, test to confirm the cause, and explain the results in English or Spanish. All makes and models.See computer diagnostics QuestionsCar diagnostic test FAQWhat does a car diagnostic test check?It reads trouble codes, pending codes, freeze frame data, live sensor data, and readiness monitors from the engine computer and, with a professional scan tool, from other modules like ABS and airbags.Can a diagnostic find problems without a check engine light?Sometimes. Pending codes and faults in other modules can show up before any light comes on. Our article on getting a diagnostic with no warning lights covers when that's worth doing.Will clearing the code fix the problem?No. Clearing a code turns the light off, but it comes back if the fault is still there. It also resets the readiness monitors, which can cause a car to fail an emissions test until it has been driven enough to complete them.Is a code reader the same as a diagnostic scan tool?No. A basic code reader shows engine codes and descriptions. A professional scan tool also reads other modules, shows live data, and can run system tests.How long does a car diagnostic take?The scan itself takes a few minutes. Confirming the cause can take longer, especially for electrical or intermittent problems that don't happen every time. About the authorChristian owns New Level Auto Service in Rockville, MD. He has more than 20 years of experience working on cars and has run the shop for over 10 years. The shop is a licensed Maryland State Inspection station with ASE-certified mechanics who work on all makes and models. More about our shop. Bring your car to New Level Auto ServiceWe're at 716 E Gude Dr in Rockville, MD. Walk-ins are welcome, and calling ahead gets you in faster.Phone (301) 762-1200Hours Monday to Friday 8 AM to 5 PM, Saturday 9 AM to 2 PMExtras Night drop and 24-hour emergency towingCall nowDirections
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Vehicle Maintenance
Does Regular Car Maintenance Actually Save Money?
Yes, for most drivers regular car maintenance saves money, because a few inexpensive jobs protect the most expensive parts of the car. Oil changes protect the engine, coolant prevents overheating, brake pads replaced on time save the rotors, a timing belt changed on schedule can save the engine, and tire care makes tires last longer. Good service records also help at resale. Quick answerMaintenance pays off when a small wear item protects a big, expensive part.The biggest savings come from oil changes, coolant, brakes, belts and tires.Skipping these can turn a routine job into engine, rotor or tire replacement.A documented service history makes a used car easier to sell and easier to trust.Follow your owner's manual. Extra services it doesn't call for rarely save you anything. How does maintenance actually save money? Most car maintenance follows the same pattern. An inexpensive part wears out so that an expensive part doesn't. Oil wears out so the engine bearings don't. Brake pads wear down so the rotors and calipers don't. When the inexpensive part is replaced on time, the expensive part lasts. When it isn't, the damage moves up the line. That's the honest case for maintenance. It won't make a car last forever, and not every service on every menu is worth doing. But a small list of jobs prevents the most expensive failures we see in the shop, and those are the ones worth never skipping. The rest of this article covers them one by one. Why are oil changes the most important maintenance? Oil keeps the moving parts inside your engine from grinding against each other. Over time it breaks down, collects dirt and loses its ability to protect. Old or low oil speeds up wear on bearings, the timing chain and other internal parts, and severe oil neglect can ruin an engine. An oil change is one of the least expensive services on a car. An engine replacement is one of the most expensive repairs. Our general rule is every 5,000 miles or six months, whichever comes first, unless your owner's manual says otherwise. Check the oil level once a month too, because an engine that burns or leaks oil can run low between changes. See our oil change service for what's included. If an engine has already been damaged, it becomes an engine repair job, which is exactly what routine oil changes help you avoid. How do coolant and belts protect the engine? Coolant keeps the engine from overheating in summer traffic and from freezing in winter. It also contains additives that protect the radiator, water pump and engine from corrosion, and those additives wear out over time. An engine that overheats badly can warp the cylinder head or blow a head gasket, which is a major repair. Replace coolant at the interval in your owner's manual, fix leaks early, and have the cooling system checked if the temperature gauge climbs or you smell something sweet. The timing belt, on engines that have one, keeps the valves and pistons moving in sync. Many manufacturers call for replacement somewhere between 60,000 and 100,000 miles, but it varies a lot, so check the manual. On many engines, if the belt breaks, the valves and pistons can hit each other, and a routine belt job becomes serious engine damage. Engines with a timing chain usually don't need scheduled replacement, but chains depend on clean oil to last. The serpentine belt runs the alternator, A/C and often the water pump. A cracked belt is inexpensive to replace. A belt that snaps on the highway can leave you stranded, and if it drives the water pump, the engine can overheat quickly. Why is it cheaper to replace brakes and tires on time? Brakes are the clearest example of paying a little now or more later. Most brake pads last somewhere between 30,000 and 70,000 miles, depending on the car and how you drive. When pads wear down to the metal, they start grinding into the rotors. A pad replacement then turns into pads and rotors, and sometimes calipers. Squealing is often the built-in wear indicator telling you it's time. Grinding means it's past time. Our brake repair page explains the warning signs. Tires last longer with three simple habits: Keep them at the pressure on the driver's door sticker. Underinflated tires wear out faster and hurt fuel economy. Rotate them on the schedule in your manual, often every 5,000 to 7,500 miles, so they wear evenly. Get the alignment checked after hitting a big pothole or if the car pulls. Bad alignment can wear the inside edge of a tire down long before the rest of the tread. Maryland roads make this matter more. Pothole season every spring is hard on alignment and suspension, and a worn part can quietly chew through a set of tires. Does regular maintenance help resale value? It helps. Buyers and dealers look for a car that has been cared for, and a folder of service records is proof. A car with documented oil changes, brake work and timing belt replacement is easier to trust than one with no history, and that usually makes it easier to sell and easier to negotiate on. Keep every receipt, or at least a simple log with the date, mileage and work done. Fix small problems, like warning lights and leaks, before you list the car. Buyers notice them. Remember that in Maryland, a used car needs to pass a safety inspection when it's sold, titled or transferred. A car that's been maintained is much more likely to pass without surprises. We're a licensed station for the Maryland State Inspection, and certificates are sent to the MVA electronically. When is maintenance not worth the money? Not every recommended service saves you money. The owner's manual lists what your car actually needs and when. Services outside that schedule may not do much for your car. A few practical rules: Use the manual as your baseline, and adjust for how you drive. Lots of short trips, towing or heavy traffic can mean more frequent service. Ask why a service is recommended and what happens if you wait. A good mechanic can show you the worn part or the test result. Put safety and engine protection first: brakes, tires, oil, coolant and belts. On an older car, weigh a big repair against what the car is worth and how long you plan to keep it. Sometimes the honest answer is that it isn't worth fixing. Keep up with the maintenance that mattersOur ASE-certified mechanics change your oil with the grade your manufacturer calls for and check fluids, belts and tires while the car is in.See our oil change service QuestionsCar maintenance cost FAQ Does regular car maintenance really save money?For most cars, yes. Oil changes, coolant service, brake pads, belts and tire care cost far less than the engine, rotor and tire damage they help prevent. What maintenance should never be skipped?Oil changes, brake inspections, coolant, the timing belt if your engine has one, and tire pressure and rotation. Those protect the most expensive and most safety-critical parts of the car. Do service records increase a car's resale value?They help. A documented history shows buyers the car was cared for, which usually makes it easier to sell and easier to negotiate on. Should I follow the dealer's schedule or the owner's manual?The owner's manual is the baseline, because it's what the manufacturer says your car needs. Adjust for severe driving, like short trips, towing or heavy traffic. Does a well-maintained car pass the Maryland inspection more easily?Usually. Items like brakes, tires, lights and suspension are checked, and a car that's kept up is less likely to need repairs before it passes the Maryland State Inspection. About the authorChristian owns New Level Auto Service in Rockville, MD. He has more than 20 years of experience working on cars and has run the shop for over 10 years. The shop is a licensed Maryland State Inspection station with ASE-certified mechanics who work on all makes and models. More about our shop. Bring your car to New Level Auto ServiceWe're at 716 E Gude Dr in Rockville, MD. Walk-ins are welcome, and calling ahead gets you in faster.Phone (301) 762-1200Hours Monday to Friday 8 AM to 5 PM, Saturday 9 AM to 2 PMExtras Night drop and 24-hour emergency towingCall nowDirections
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Vehicle Maintenance
Should You Get a Car Diagnostic With No Warning Lights?
Usually not. If your car runs normally, no warning lights are on, and you keep up with regular maintenance, a routine car diagnostic rarely turns up anything useful. A diagnostic scan does make sense in a few specific situations: before you buy a used car, before a long road trip, when a problem comes and goes, and before a Maryland State Inspection if a light has been flickering. Quick answerA routine scan isn't needed if the car runs fine and no lights are on. The car's computer already watches itself.Before buying a used car, a scan can reveal recently cleared codes and faults in other systems.Before a long trip, pair a scan with a check of the brakes, tires, fluids, and battery.For problems that come and go, stored and pending codes can point in the right direction.Before a Maryland State Inspection, a scan helps mainly if a warning light has been coming on and off. Do you need a car diagnostic if no warning lights are on? Most of the time, no. Your car's computers check the engine, emissions, and several other systems every time you drive. When they confirm a problem, they turn on a warning light. If nothing is lit and the car starts, runs, stops, and drives the way it always has, a scan is unlikely to find anything worth fixing. What keeps a healthy car healthy is regular maintenance, not regular scanning. That means oil changes on schedule, fluids and filters at the intervals in your owner's manual, and a mechanic looking at the brakes, tires, belts, and hoses. Most of those parts don't have sensors, so a scan can't see them anyway. There are exceptions, though. The computer stores pending codes for faults it has seen but not confirmed, and it can log problems in systems like ABS or airbags that don't always light the check engine light. The situations below are where looking for those makes sense. Should you scan a used car before you buy it? Yes, this is one of the best times to do it. A seller can clear the codes and turn off the check engine light right before you look at the car. A scan can still catch that, because clearing codes also resets the car's readiness monitors. If several monitors show "not ready," the codes were cleared recently or the battery was disconnected, and you should ask why. A good pre-purchase scan also reads the other modules, not just the engine. Stored codes in the ABS, airbag, or body computers can point to problems a test drive won't show you. A scan is only one part of checking a used car. Brakes, suspension, tires, leaks, and rust need a hands-on look. If you're buying a used car in Maryland, it will also need to pass a Maryland State Inspection before it can be titled and registered, so it's worth knowing what you're getting into first. Is a diagnostic worth it before a road trip? It can be, as part of a bigger pre-trip check. A scan may catch pending codes, like an early misfire or a sensor starting to fail, that could turn into a warning light halfway to your destination. It's a small part of the picture, though. For a long drive, the things that most often leave people stranded are: A weak battery, especially in very hot or very cold weather Worn brakes or low tire tread Low coolant, or old hoses and belts Low or overdue oil A battery and charging test is quick and catches a lot. If yours is getting old or slow to crank, have the battery, alternator, and starter tested before you go. What if the problem comes and goes? Intermittent problems are where a scan earns its keep, even with no light on right now. A check engine light that came on and went off, a stall that happens once a week, or hesitation only when the engine is warm can all leave stored or pending codes behind. Freeze frame data shows the speed, temperature, and load when the fault happened, which helps a mechanic recreate it. A few things make intermittent problems easier to find: Don't clear the codes or disconnect the battery. That erases the evidence. Write down when it happens: cold or warm engine, speed, weather, and what you were doing. Bring the car in while the problem is happening, if you safely can. If the light comes back on and stays on, our check engine light page covers what it usually means. Should you get a scan before a Maryland State Inspection? Only in some cases. The Maryland State Inspection is mainly a hands-on safety check of things like brakes, steering, suspension, tires, lights, and other equipment. Most of those problems won't show up on a computer scan. Emissions testing in Maryland is a separate program, so the safety inspection isn't a computer emissions test. A scan before inspection is most useful when a warning light for a safety system, such as ABS or airbags, has been flickering on and off. Knowing the cause ahead of time lets you fix it before the inspection instead of after. We're a licensed Maryland State Inspection station, and certificates are sent to the MVA electronically. Buying a used car or chasing an odd problem?Our ASE-certified mechanics read the codes, check the readiness monitors, and test to confirm the cause on all makes and models.See computer diagnostics QuestionsDiagnostics with no warning lights FAQHow often should I get a car diagnostic?There's no set schedule. Get one when a warning light comes on, when you notice a new symptom, or in special cases like buying a used car or chasing a problem that comes and goes.Can a diagnostic find problems before symptoms appear?Sometimes. Pending codes can show up before the check engine light, but many wear items like brake pads, tires, and suspension parts never set a code at all.Can a scan tell if someone cleared the codes?Usually, yes. Clearing codes resets the readiness monitors, and several monitors showing "not ready" is a sign the codes were cleared or the battery was disconnected recently.Does the Maryland State Inspection include an emissions test?No. The safety inspection covers equipment like brakes, steering, suspension, tires, and lights, while emissions testing is handled by a separate state program. Our Maryland State Inspection page has the details.What does a car diagnostic actually show?It shows trouble codes, pending codes, freeze frame data, live sensor readings, and readiness monitors. Our guide on what a car diagnostic test tells you explains each one. About the authorChristian owns New Level Auto Service in Rockville, MD. He has more than 20 years of experience working on cars and has run the shop for over 10 years. The shop is a licensed Maryland State Inspection station with ASE-certified mechanics who work on all makes and models. More about our shop. Bring your car to New Level Auto ServiceWe're at 716 E Gude Dr in Rockville, MD. Walk-ins are welcome, and calling ahead gets you in faster.Phone (301) 762-1200Hours Monday to Friday 8 AM to 5 PM, Saturday 9 AM to 2 PMExtras Night drop and 24-hour emergency towingCall nowDirections
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Car Troubleshooting
Why Is My Car AC Blowing Warm Air?
Car AC blowing warm air? The most common cause is low refrigerant from a leak. Other common causes are a compressor or compressor clutch that isn't engaging, a condenser fan that has stopped working, a blown fuse or relay, or a stuck blend door. A few quick checks can narrow it down, but most AC fixes need proper gauges and leak testing. Quick answerThe number one cause is a refrigerant leak. AC systems are sealed, so low refrigerant means it's escaping somewhere.Other usual suspects: compressor or clutch failure, condenser fan problems, electrical faults, and blend door actuators.You can check the AC settings, the cabin air filter, fuses, and whether the compressor and fans come on.DIY recharge cans don't fix leaks, can overcharge the system, and some contain sealant that causes bigger problems.Cold at highway speed but warm at idle often points to the condenser fan. Why is my car AC blowing warm air? Your AC works by pumping refrigerant through a loop: the compressor squeezes it, the condenser in front of the radiator sheds heat, and the evaporator behind the dash gets cold and chills the air blowing past it. If any part of that loop fails, the air coming out of the vents stays warm. These are the causes we see most often: Low refrigerant from a leak. Refrigerant doesn't get "used up." If it's low, there is a leak at a hose, O-ring, the condenser, the compressor seal, or the evaporator. Compressor or compressor clutch problems. The compressor is the heart of the system. If its clutch won't engage or the compressor itself is worn out, nothing gets cold. Condenser fan not working. The condenser needs airflow to release heat. At highway speed, air rushes through on its own. At a stoplight, the electric fan has to do that job. A dead fan usually means cold air while moving and warm air at idle. Electrical faults. A blown fuse, a bad relay, a failed pressure switch, or a damaged wire can keep the compressor from turning on even when everything else is fine. Blend door actuator. A small motor behind the dash controls how much air passes over the heater core. If it sticks on the heat side, you get warm air no matter what you set. Clicking behind the dash is a common clue. Clogged cabin air filter. This mostly weakens airflow, but a badly clogged filter can make the AC feel like it's barely working. What can you check yourself? These checks are safe and quick. Do them with the car parked and the parking brake on: Confirm the settings. Make sure the AC button is on, the temperature is set to cold, and the fan is running. On automatic systems, try recirculation mode on a hot day. Watch the compressor. With the engine running and AC on max, look at the front of the compressor pulley. The center part should spin with the pulley and you may hear a click when it engages. If it never engages, the problem may be low refrigerant or electrical. Look at the condenser fans. With the AC on, the electric fan or fans behind the grille should usually run. If they don't, that's a strong clue. Check the front of the condenser. Leaves, bugs, and dirt packed against the condenser block airflow. Look through the grille for obvious debris. Check the cabin air filter. On many cars it's behind the glove box. A filter packed with dust and leaves cuts airflow. Most need replacement every 15,000 to 30,000 miles, or about once a year. Check the fuses. Your owner's manual shows which fuse and relay control the AC. A blown fuse is easy to spot. Notice the pattern. Warm only at idle, warm only on one side, warm after 20 minutes of driving, or warm all the time? Each pattern points to different parts. Also look for oily residue on AC hoses and fittings. Refrigerant carries oil, so an oily spot often marks the leak. Should you use a DIY AC recharge can? We don't recommend using a recharge can without knowing why the system is low. Here's why: It doesn't fix the leak. If refrigerant leaked out once, the new charge will leak out too. You may get a few weeks of cold air and then be back where you started. Overcharging is easy. The small gauge on a can only reads one side of the system and doesn't account for outside temperature well. Too much refrigerant raises pressures, makes cooling worse, and can damage the compressor. Sealant can cause more damage. Many cans include a stop-leak sealant. It can clog small passages like the expansion valve or orifice tube, and it can contaminate a shop's recovery equipment, which is why many shops test for it before working on a system. Your car may use a different refrigerant. Many newer vehicles use R-1234yf instead of the older R-134a. They are not interchangeable. The correct type is printed on a label under the hood. It may not be the refrigerant at all. If the problem is a fan, fuse, or blend door, refrigerant won't help. The right way to recharge an AC system is to recover what's left, pull a vacuum to remove air and moisture, check that it holds, and refill with the exact amount by weight listed for your car. What needs a mechanic? Once the easy checks are done, most AC problems need tools a driveway doesn't have. During an auto AC repair diagnosis, a mechanic will typically read high-side and low-side pressures, check the compressor clutch circuit, and look for leaks using UV dye or an electronic leak detector. Electrical problems may call for computer diagnostics, since many AC systems are controlled by modules that store trouble codes. Bring the car in soon if you notice any of these: Grinding, squealing, or rattling when the AC turns on. A failing compressor can shed metal through the whole system if it's ignored. A burning smell or smoke from the vents or under the hood. The engine temperature gauge climbing while the AC is on. The condenser sits in front of the radiator, and a bad fan can affect both. Our cooling system repair page covers that side of things. How can you keep your AC working longer? Run the AC for about 10 minutes at least once a month, even in winter. The refrigerant carries oil that keeps seals from drying out. The defroster setting on many cars runs the compressor automatically. On a hot day, open the windows or run the fan for a minute first to push the hot air out, then switch to AC. Replace the cabin air filter on schedule. Get a slow leak checked in spring, before it turns into a failed compressor in July. AC still blowing warm?We check pressures, test for leaks, and diagnose the compressor, fans, and electrical side so you know what's actually wrong before anything gets replaced.See our AC repair service QuestionsWarm car AC FAQ Why does my car AC blow cold while driving but warm at idle?That usually points to the condenser fan. At speed, air flows through the condenser on its own, but at idle the electric fan has to move the air, so a weak or dead fan shows up at stoplights first. Does car AC refrigerant need to be topped off regularly?No. The AC is a sealed system, so it shouldn't lose refrigerant under normal use. If it's low, there's a leak that should be found and fixed. Why is my AC cold on one side and warm on the other?On cars with dual-zone climate control, this is often a blend door actuator stuck on one side. Low refrigerant can also cause it on some vehicles. Can a bad AC compressor damage the rest of the system?Yes. A compressor that fails internally can send metal debris through the hoses, condenser, and valves. That's why a noisy compressor should be checked before it fails completely. Is it safe to drive with a broken car AC?Usually yes, as long as there's no burning smell, loud grinding, or rising engine temperature. Without AC, the windshield can fog more easily, so use the defroster and fresh air to keep it clear. About the authorChristian owns New Level Auto Service in Rockville, MD. He has more than 20 years of experience working on cars and has run the shop for over 10 years. The shop is a licensed Maryland State Inspection station with ASE-certified mechanics who work on all makes and models. More about our shop. Bring your car to New Level Auto ServiceWe're at 716 E Gude Dr in Rockville, MD. Walk-ins are welcome, and calling ahead gets you in faster.Phone (301) 762-1200Hours Monday to Friday 8 AM to 5 PM, Saturday 9 AM to 2 PMExtras Night drop and 24-hour emergency towingCall nowDirections
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Car Troubleshooting
Signs of a Failing Alternator While Driving
The most common signs of a failing alternator while driving are a battery-shaped warning light on the dash, headlights or dash lights that dim or flicker, electrical features acting up, a whining or grinding noise from the engine, and a burning rubber or electrical smell. If you see these, turn off extra electrical loads and get the charging system tested soon. Quick answerThe battery light usually means the charging system has a problem, not necessarily the battery.Dim or flickering lights, slow power windows, and a radio that resets are classic alternator clues.Most alternators last about 7 to 10 years or roughly 80,000 to 150,000 miles.A car that dies while driving points to the alternator. A car that won't start after sitting points more to the battery.With a dead alternator, the car runs on battery power alone and can stall within minutes to an hour. What does an alternator do? The alternator is a small generator driven by the engine through a belt. While the engine runs, it makes electricity to power the headlights, ignition, fuel pump, computers, climate fan, and everything else, and it recharges the battery at the same time. The battery's main job is to start the car. After that, the alternator carries the electrical load. That's why a failing alternator often shows up while you're driving, and a weak battery usually shows up when you try to start. What are the warning signs of a failing alternator while driving? Alternators rarely die all at once. They usually give some warning first. Watch for these signs: Battery or charging warning light. This light is shaped like a battery, and on some cars it reads "ALT" or "GEN." It comes on when the charging voltage is too low or too high. The battery symbol confuses people, but it usually points to the alternator, its belt, or the wiring. Dim or flickering lights. Headlights, dash lights, or interior lights that dim at idle and brighten when you rev the engine are a common early sign. So are lights that pulse or flicker. Electrical glitches. Power windows moving slowly, the radio resetting, the climate fan weakening, gauges jumping around, or several warning lights coming on at once can all come from low voltage. Modern cars are full of modules that act strangely when voltage drops. Whining or grinding noise. A high-pitched whine that rises with engine speed can come from worn alternator bearings or internal problems. Grinding or rattling usually means the bearings are getting worse. Burning smell. A hot rubber smell can mean the belt is slipping on the alternator pulley. An electrical, burning-wire smell can mean the alternator is overheating from working too hard. Either one should be checked right away. A battery that keeps going dead. If the battery is new or tests fine but keeps running down, the alternator may not be recharging it. A bad alternator can also shorten the life of a good battery. Stalling or rough running. Once voltage gets low enough, the ignition and fuel system can't work properly, and the engine may stall. A failing alternator can also turn on the check engine light, since many cars store charging system trouble codes. Can a bad alternator cause the engine to overheat? Not directly. The alternator makes electricity. It doesn't cool the engine. The confusion usually comes from the serpentine belt. On many engines, one belt drives the alternator, the water pump, the power steering pump, and the AC compressor. If that belt breaks or comes off, perhaps because a seized alternator pulley shredded it, the water pump stops too. Then you can see the battery light and the temperature gauge climbing at the same time. If both of those happen together, pull over safely and shut the engine off. Driving with a broken belt can overheat the engine quickly and cause serious damage. If the temperature gauge climbs on its own, without the battery light, that's a cooling problem, and our cooling system repair page is a better place to start. What should you do if the battery light comes on while driving? Turn off what you don't need. Switch off the AC or heater fan, heated seats, the radio, and phone chargers. This stretches the battery power you have left. Keep headlights on if you need them to be seen. Safety comes first, especially at night or in rain. Watch the temperature gauge. If it climbs, the belt may be broken. Pull over and shut the engine off. Don't turn the engine off until you're somewhere safe. With a failing alternator, the car may not restart once you shut it down. Head straight to a shop or home. A car running on battery alone might go anywhere from a few minutes to about an hour, depending on the battery and how much is running. If the car won't make it, we offer 24-hour emergency towing to our shop in Rockville. How long do alternators usually last? Most alternators last about 7 to 10 years, or roughly 80,000 to 150,000 miles. Some go much longer. Lots of short trips, heavy electrical loads like aftermarket stereos or extra lights, heat, and oil or coolant leaking onto the alternator can all shorten its life. A worn or loose belt can make the alternator work harder or charge poorly, so belts are worth checking during regular maintenance. For comparison, most car batteries last about 3 to 5 years. Heat is hard on batteries, and the DC area's hot summers take a toll. Is it the battery or the alternator? The two are easy to mix up, because a bad alternator leaves you with a dead battery. These patterns help tell them apart: Car starts with a jump and runs fine, but won't start the next morning. This points to the battery, or to something draining it overnight. Car starts with a jump but dies again while driving, or the battery light stays on. This points to the alternator. Lights dim while driving and get worse over time. Likely the alternator. Slow, labored cranking in cold weather with a battery over 4 years old. Likely the battery. Click but no crank, with bright dash lights. That can be the starter, not the battery or alternator. We cover starting problems in more detail in our guide on whether a car that won't start needs a battery, alternator, or starter. A real test is quick. With the engine off, a healthy, fully charged battery reads about 12.6 volts. With the engine running, a working charging system usually reads about 13.5 to 14.7 volts. When we do battery, alternator, and starter testing, we also load-test the battery and check the alternator's output under load. One old trick to avoid: don't disconnect the battery cable with the engine running to "test" the alternator. On modern cars, that voltage spike can damage electronics. Battery light on or lights dimming?We test the battery, alternator, and starter so you replace only the part that has actually failed.Battery, alternator and starter service QuestionsFailing alternator FAQ How long can you drive with a bad alternator?It depends on the battery's charge and how much electrical load is running, but usually somewhere from a few minutes to about an hour. Turn off extra accessories and drive straight to a shop. Can a bad alternator ruin a new battery?Yes. An alternator that undercharges leaves the battery deeply drained over and over, which shortens its life. One that overcharges can overheat the battery. Does the battery light always mean a bad battery?No. The battery light is a charging system warning. It usually points to the alternator, the drive belt, or the wiring rather than the battery itself. What does a bad alternator sound like?Usually a whine that rises and falls with engine speed, or a grinding or rattling noise from worn bearings. A squeal on startup is more often a loose or worn belt. Can you test an alternator at home?You can get a rough idea with a multimeter: about 12.6 volts with the engine off and about 13.5 to 14.7 volts with it running. A load test at a shop gives a more reliable answer. About the authorChristian owns New Level Auto Service in Rockville, MD. He has more than 20 years of experience working on cars and has run the shop for over 10 years. The shop is a licensed Maryland State Inspection station with ASE-certified mechanics who work on all makes and models. More about our shop. Bring your car to New Level Auto ServiceWe're at 716 E Gude Dr in Rockville, MD. Walk-ins are welcome, and calling ahead gets you in faster.Phone (301) 762-1200Hours Monday to Friday 8 AM to 5 PM, Saturday 9 AM to 2 PMExtras Night drop and 24-hour emergency towingCall nowDirections
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Vehicle Maintenance
7 Brake Myths vs. Facts Every Driver Should Know
Most brake maintenance myths lead drivers to wait too long. The facts: a brief squeak on a damp morning is normal, but a steady squeal, grinding, a soft pedal, or a pulsing pedal are not. Brake fluid wears out even when the brakes feel fine, and a lit ABS light usually means regular braking still works but anti-lock does not. Quick answerA light squeak that goes away after a few stops is usually moisture or surface rust. Grinding is never normal.Replace pads before they wear down to metal. Waiting costs you rotors and stopping distance.A soft, sinking, or very hard brake pedal is a warning sign, not a quirk of an older car.Many manufacturers call for new brake fluid every 2 to 3 years. Your owner's manual has the exact interval.New pads don't always need new rotors. It depends on rotor thickness and condition. Is brake noise normal? Myth: Brakes make noise, so noise doesn't mean anything. Fact: Some noise is normal and some is not. A light squeak or scraping sound on the first few stops after rain, a car wash, or a night parked outside is usually a thin layer of rust on the rotors. It wipes off in a few stops and goes away. These sounds are different and worth a visit: A steady high-pitched squeal on most stops. Many brake pads have a small metal tab called a wear indicator. It rubs the rotor and squeals when the pad is getting thin, usually around 2 to 3 mm of material left. Grinding or growling. This often means the pad material is gone and metal is rubbing on metal, or a rock or piece of debris is caught in the brake. Get it checked right away. Clicking or clunking when you brake. Loose or missing hardware can let the pads shift in the caliper. Can you wait until your brakes stop working? Myth: You only need new brakes when they stop working. Fact: Brakes rarely fail all at once. They wear gradually, and stopping distance gets longer so slowly that most drivers don't notice. Once the friction material is gone, the steel backing plate grinds into the rotor. That can ruin the rotor, overheat the caliper, and turn a simple pad replacement into a much bigger brake job. The smart time to replace pads is when a mechanic measures them at around 3 mm, or when the wear indicator starts to squeal. A brake inspection once a year, or at every tire rotation, catches this early. Should you have to press hard on the brake pedal? Myth: As a car gets older, you just have to push the pedal harder. Fact: Modern brakes are power-assisted. A healthy pedal feels firm and stops the car with moderate pressure, the same way every time. A change in how the pedal feels usually points to a specific problem: Soft or spongy pedal: often air or moisture in the brake fluid, or a small leak. Pedal slowly sinks toward the floor at a stop: possible master cylinder or hydraulic problem. Don't keep driving it. Very hard pedal that takes a lot of effort: often a brake booster or vacuum supply problem. Glazed or contaminated pads can also cause it. Pedal pulses when you stop: usually uneven rotor thickness, often called warped rotors. Does brake fluid matter if the brakes work fine? Myth: If the brakes work, the fluid is fine. Fact: Most brake fluid (DOT 3, DOT 4, and DOT 5.1) absorbs moisture from the air over time. Water in the fluid lowers its boiling point, so under hard or repeated braking, like a long downhill, the fluid can boil and the pedal goes soft. Moisture also corrodes brake lines, calipers, and the ABS unit from the inside. Old fluid can look fine and still be worn out, which is why it's replaced on a time schedule, often every 2 to 3 years. Myth: Low brake fluid just needs a top-off. Fact: The fluid level drops slowly as pads wear, because the caliper pistons move outward to follow them. A low reservoir usually means worn pads or a leak. Topping it off hides the warning without fixing the cause, so have the pads and lines checked first. Do you need new rotors with every brake job? Myth: Rotors always have to be replaced with the pads. Fact: Not always. Every rotor has a minimum thickness stamped on it. If the rotor is above that number, smooth, and not causing a pulsing pedal, it can often stay. Rotors need replacing when they're below minimum thickness, deeply grooved, cracked, badly rusted, or showing hard spots from overheating. Many modern rotors are thin to begin with, so replacing them is often the better choice, but it should be based on measurement, not habit. Does the ABS light mean your brakes will fail? Myth: If the ABS light is on, you have no brakes. Fact: In most cars, an ABS light on its own means the anti-lock system has shut itself off because of a fault, often a wheel speed sensor or its wiring. Your normal brakes usually still work, but the wheels can lock up in a hard stop or on wet and icy roads. If the red BRAKE light comes on too, treat it as more serious and have it checked before driving. Our ABS repair page explains the common causes. Brakes feel or sound different?Our ASE-certified mechanics check pads, rotors, calipers, lines, and brake fluid on all makes and models, and we explain what we find in English or Spanish.See brake repair QuestionsBrake maintenance myths FAQHow often should brakes be inspected?Once a year or at every tire rotation is a good rule, plus any time the noise or pedal feel changes. Brakes are also checked as part of the Maryland State Inspection.Are disc brakes better than drum brakes?Disc brakes shed heat better and recover faster when wet, which is why nearly every car has them in front. Drum brakes are still common on the rear of many cars and light trucks and work well when they're adjusted and maintained.Is it safe to drive with squeaky brakes?A squeak that goes away after a few stops is usually harmless. A squeal on most stops often means the pads are getting thin, and grinding means you should get the car checked as soon as possible.How long do brake pads last?Most brake pads last between 30,000 and 70,000 miles, depending on the car and how it's driven. Our guide on how long brake pads last covers what wears them out faster.Do I need to change brake fluid if it looks clean?Yes, if it's due by time or mileage in your owner's manual. Brake fluid absorbs moisture you can't see, so color alone doesn't tell you if it's still good. About the authorChristian owns New Level Auto Service in Rockville, MD. He has more than 20 years of experience working on cars and has run the shop for over 10 years. The shop is a licensed Maryland State Inspection station with ASE-certified mechanics who work on all makes and models. More about our shop. Bring your car to New Level Auto ServiceWe're at 716 E Gude Dr in Rockville, MD. Walk-ins are welcome, and calling ahead gets you in faster.Phone (301) 762-1200Hours Monday to Friday 8 AM to 5 PM, Saturday 9 AM to 2 PMExtras Night drop and 24-hour emergency towingCall nowDirections
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Car Troubleshooting
Check Engine Light On? What to Do (Steady vs. Flashing)
If your check engine light is steady, the car is usually safe to drive for now, but get the code read within a few days. If it's flashing, the engine is misfiring badly enough to damage the catalytic converter. Slow down, avoid hard acceleration, and stop driving as soon as it's safe. Check the gas cap first, then get a proper diagnosis. Quick answerSteady light: not an emergency. Drive normally and get it checked soon.Flashing light: serious misfire. Pull over when safe and don't keep driving.Red oil pressure or temperature lights with it: stop and shut the engine off.A loose gas cap is a common cause, but the light can take a few days of driving to go off after you tighten it.A code tells you where to look, not exactly what part to replace. What does the check engine light mean? The check engine light, also called the malfunction indicator lamp, comes on when your car's computer detects a problem with the engine, ignition, fuel, or emissions system. When it turns on, the computer stores a diagnostic trouble code, such as P0301 or P0420, that points to the system involved. The light itself doesn't tell you how serious the problem is. It covers everything from a loose gas cap to a failing catalytic converter. What it does tell you is to pay attention, and whether it's steady or flashing is your first clue. Steady vs. flashing: is it safe to keep driving? A steady check engine light means the computer found a fault, but nothing is likely to fail in the next few minutes. You can usually keep driving normally. Still, don't ignore it for weeks. A small problem like a failing oxygen sensor can hurt fuel economy and, over time, damage more expensive parts. A flashing check engine light means the engine is misfiring badly. Unburned fuel is going into the exhaust, where it can overheat the catalytic converter and ruin it quickly. If it's flashing: Ease off the gas and slow down. Hard acceleration makes it worse. Don't tow anything or climb long hills if you can avoid it. Get off the road when it's safe and turn the engine off. Have the car towed, or drive only a very short distance gently if you have no choice. Some other signs mean stop right away, no matter what the check engine light is doing: The red oil pressure light comes on. The temperature gauge goes into the red or a red temperature light comes on. You smell burning, see smoke, or hear loud knocking. The car suddenly loses power or shakes hard. What should you check first? A few simple checks can help before you bring the car in: Check the gas cap. Take it off and put it back on until it clicks. Look for a cracked seal. A loose cap causes an evaporative (EVAP) system leak code. The light won't go off right away. It usually takes a few days of normal driving for the computer to recheck the system. Look at the other warning lights. Oil pressure, temperature, battery, and brake lights tell you more about what's going on and how urgent it is. Notice how the car drives. Rough idle, shaking, hesitation, stalling, a loss of power, or worse gas mileage all help narrow things down. Write down when it happens: cold starts, highway speed, at idle, or in the rain. Check the oil and coolant. With the engine off and cool, check the oil on the dipstick and the coolant level in the overflow tank. Never open a hot radiator cap. If everything looks normal and the car drives fine, it's still worth getting the code read. The light being on also hides new problems, because it can't come on "again" to warn you about a second fault. What are the most common causes? These are the causes we see most often when a check engine light comes on: Loose or damaged gas cap. The easiest fix, and a common one. EVAP system leaks. Cracked hoses, a bad purge valve, or a vent valve in the fuel vapor system. Oxygen sensors. They measure exhaust oxygen to help set the fuel mixture. A bad one hurts fuel economy. Spark plugs and ignition coils. Worn plugs or a failing coil cause misfires and are a very common reason for a flashing light. Regular tune-ups help prevent this. Mass airflow sensor. A dirty or failing sensor can cause hesitation, rough idle, and poor mileage. Catalytic converter. Often a result of other problems, like long-term misfires or burning oil. Our exhaust and muffler repair page covers that part of the system. Vacuum leaks and thermostat problems. Cracked vacuum hoses and a thermostat stuck open are also frequent causes. Is a free code scan enough? A code reader, including the free scans some parts stores offer, is a good start. It tells you which system flagged the problem. But a code isn't a diagnosis. A P0420 code, for example, says the catalytic converter isn't working efficiently, but the real cause might be an oxygen sensor, an exhaust leak, or a misfire. Replacing parts based only on the code can waste money and leave the real problem in place. A full diagnosis uses a professional scan tool to look at live sensor data, freeze frame data from when the fault happened, and readiness monitors, then tests the suspect parts directly. That's what our check engine light service and computer diagnostics cover. One more tip: don't just clear the code and hope. Clearing it erases useful information, and the light will come back if the problem is still there. It also resets the readiness monitors, which can cause a car to fail an emissions test until it's been driven enough to set them again. In Maryland, a check engine light that's on will also keep your car from passing the MVA's emissions (VEIP) test. Check engine light still on?We read the codes, check live data, and test the parts involved so you know the actual cause before you pay for a repair.Check engine light service QuestionsCheck engine light FAQ Can I drive with the check engine light on?If it's steady and the car drives normally, yes, for a short time. If it's flashing, or if the oil pressure or temperature light is also on, stop driving as soon as it's safe. How long does it take for the light to go off after tightening the gas cap?Usually a few days of normal driving. The computer has to run its EVAP self-test again before it turns the light off, so it won't happen right away. Why is my check engine light flashing?A flashing light almost always means a severe engine misfire. It can quickly overheat and damage the catalytic converter, so slow down and stop driving when it's safe. Will a check engine light go off by itself?Sometimes. If the problem was temporary, like a loose gas cap, the light can turn off after the computer rechecks the system. The code usually stays stored for a while, so it's still worth having it read. Can you check my engine light without an appointment?Yes. Walk-ins are welcome at our Rockville shop, but calling ahead at (301) 762-1200 gets you in faster. About the authorChristian owns New Level Auto Service in Rockville, MD. He has more than 20 years of experience working on cars and has run the shop for over 10 years. The shop is a licensed Maryland State Inspection station with ASE-certified mechanics who work on all makes and models. More about our shop. Bring your car to New Level Auto ServiceWe're at 716 E Gude Dr in Rockville, MD. Walk-ins are welcome, and calling ahead gets you in faster.Phone (301) 762-1200Hours Monday to Friday 8 AM to 5 PM, Saturday 9 AM to 2 PMExtras Night drop and 24-hour emergency towingCall nowDirections
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