Car questions, answered
Straight answers to the questions drivers ask us most: what a warning light means, whether a noise can wait, and how to keep a car running right. Written by a San Mateo shop that would rather you understand your car.
Warning lights
Dashboard warning lights explainedDashboard lights follow a color code. Red means stop or act now (oil pressure, engine temperature, brakes, charging). Amber or yellow means something…Why is my check engine light on?A steady check engine light means the car's computer has detected a fault in the engine, emissions or fuel system and stored a trouble code. Check…Is it safe to drive with a flashing check engine light?A flashing check engine light means the engine is actively misfiring badly enough to damage the catalytic converter. Drive only as far as you need…Why is my tire pressure light on?A steady tire pressure (TPMS) light means at least one tire is at least 25% below its recommended pressure, often because cold mornings lower the…What does the battery warning light mean?The battery-shaped light usually means the charging system isn't keeping up, most often a failing alternator, a worn or broken serpentine belt, or a…What should I do if the oil pressure light comes on?Pull over safely and turn the engine off as soon as you can. The red oil can light means oil pressure is too low to protect the engine, and driving…Why is my brake warning light on?First make sure the parking brake is fully released. If the red brake light stays on, the brake fluid is likely low, which usually means the pads are…
Noises and how it drives
Why are my brakes squeaking?A light squeak for the first few stops on a damp morning is usually surface rust on the rotors and goes away on its own. A sharp, high-pitched squeal…Why do my brakes grind when I stop?Grinding when you brake usually means the pad material is gone and the metal backing plate is scraping the rotor. That damages the rotor quickly and…Why does my steering wheel shake when I brake?A steering wheel that shakes, or a brake pedal that pulses, when you slow down is usually caused by front rotors that have worn unevenly, often…Why does my car pull to one side?Start by checking that all four tires are at the right pressure, since a low tire is the most common cause. If the pressures are fine, the usual…Why is my steering wheel hard to turn or noisy?On cars with hydraulic power steering, a heavy wheel or a whine when turning usually means low fluid from a leak, a worn power steering pump or a…Why does my car clunk over bumps?A clunk or knock over bumps is most often worn sway bar end links, worn strut mounts or shocks, tired control arm bushings, or a worn ball joint. End…What's that rattling noise under my car?A metallic rattle from under the car is most often a loose exhaust heat shield, especially at certain engine speeds. A plastic flapping or scraping…Why does my car click when I turn?A rhythmic click or pop that speeds up as you accelerate through a tight turn is the classic sign of a worn outer CV (constant velocity) joint on a…Why is there a humming noise that gets louder with speed?A hum or growl that gets louder as you go faster, and doesn't change when you shift gears or rev the engine, is usually a worn wheel bearing or tires…Why does my car vibrate at highway speed?A vibration that shows up around 55 to 70 mph and fades at higher or lower speeds is most often an out-of-balance wheel, usually after a wheel weight…Why does my Honda rattle for a second on a cold start?A loud grinding or rattling sound for a second or two right after starting a cold Honda or Acura is a well-known sign of a worn VTC (variable timing…
Leaks, smells and smoke
What fluid is leaking from my car? A color guideSlide a piece of white cardboard under the car overnight and look at the color. Clear and watery near the front passenger side is usually A/C…Does a small oil leak need to be fixed right away?Not always. A slow seep that leaves only a damp film, on a car that loses little oil between changes, can often be watched and photographed at each…Why does my car smell like burning oil?Most often, oil is leaking onto a hot exhaust part and burning off. The usual source is a leaking valve cover gasket above the exhaust manifold, an…Why does my car smell sweet, like syrup?A sweet, syrupy smell almost always means coolant (antifreeze) is leaking and evaporating on a hot engine part. If the smell is inside the car,…What does the color of exhaust smoke mean?Thin white vapor that disappears as the engine warms up is just condensation, and it's normal on cool Bay Area mornings. Thick white smoke that keeps…What should I do if my car is overheating?Turn off the A/C and turn the heater to full hot with the fan on high, which pulls heat away from the engine. Pull over somewhere safe and turn the…
Won't start
Why does my car click but not start?A rapid clicking or chattering when you turn the key usually means the battery is too weak to crank the engine; a jump start will usually get you…My car won't start after sitting for weeks. What now?The most likely cause is a drained battery, since modern cars draw a small amount of power even when off. Try a jump start or a battery charger…Is it my battery or my alternator?If your car starts after a jump and then runs fine but won't restart the next morning, the battery is usually the problem. If it dies while you're…
Maintenance
How often should I change my oil?Follow your car's oil life monitor or the interval in the owner's manual, which for most modern cars on synthetic oil is somewhere between 5,000 and…What do Honda Maintenance Minder codes mean? (A, B, 1–7)Honda and Acura's Maintenance Minder shows a main code and sometimes sub-codes. "A" means replace the engine oil. "B" means replace the oil and…When does my timing belt need replacing?It depends on your engine. Most belt-driven engines call for a new timing belt somewhere between 60,000 and 105,000 miles, or after 7 to 10 years,…How often should brake fluid be changed?Most manufacturers recommend replacing brake fluid every two to three years, regardless of mileage; your owner's manual or maintenance reminder gives…Does "lifetime" transmission fluid ever need changing?Often, yes. Some manufacturers describe transmission fluid as "lifetime," but the fluid still breaks down with heat and miles, and many owner's…How long do brake pads last?Most brake pads last somewhere between 30,000 and 70,000 miles. Front pads usually wear faster than rears. Hybrids and EVs often go much longer…What's included in a 30k, 60k or 90k mile service?Major services build on a regular oil change and inspection. Around 30,000 miles, most cars add engine and cabin air filters and sometimes brake…How often should I rotate my tires?Every 5,000 to 7,500 miles is the common recommendation, which lines up with most oil changes; your owner's manual or maintenance reminder gives your…
Hybrids and EVs
Why won't my hybrid start or go into Ready mode?The most common cause is a weak 12-volt auxiliary battery, not the big hybrid battery. Hybrids use a small 12-volt battery to power the computers…Do hybrids need different maintenance?Mostly the same, with a few additions. Hybrids still need oil changes, tire rotations, brake inspections, brake fluid, filters and coolant. On top of…Can coilovers make a car ride softer?Yes, if you choose them for comfort. Coilovers are often used to lower and stiffen a car, but a quality adjustable set with appropriate spring rates…
Smart car-owner decisions
Will using an independent shop void my car's warranty?No. Under the federal Magnuson-Moss Warranty Act, a manufacturer can't void your warranty just because maintenance or repairs were done by an…How do I get a second opinion on a car repair quote?Ask the first shop for a written, itemized estimate, which California shops are required to provide. Take it to another qualified shop and ask them…What are my rights at a California auto repair shop?Under California's Automotive Repair Act, a shop must be registered with the Bureau of Automotive Repair, give you a written estimate before starting…How do I know which car repairs can wait?Sort the list into four groups. Safety items, like brakes, tires, steering and suspension joints, come first. Next is anything causing damage to…How do I find an honest mechanic?Look for a shop that shows you evidence, with photos, measurements or the old part, explains things in plain language, ranks recommendations by…What should be checked on a used car before or after buying?Have an independent mechanic inspect it, ideally before you buy or early in any return window. The essentials are brakes, tire tread and age,…Should I use OEM or aftermarket parts?Both can be the right choice. OEM (original equipment) parts are made to the manufacturer's spec and fit exactly, which matters most for sensors,…
Bay Area car life
Why did my car fail a California smog check?The most common reasons are a check engine light that's on, "readiness monitors" that haven't finished their self-tests (often after a battery change…My catalytic converter was stolen. What do I do?First, file a police report; your insurer will want the report number. Then call your insurance company, since comprehensive coverage often pays for…What should I check before a road trip?A week or so before a long trip, check tire pressure and tread (including the spare), brake condition, oil and coolant levels, the battery, wipers…
Comfort and electrical
Why is my car AC blowing warm air?The most common cause is low refrigerant from a slow leak, since A/C systems are sealed and shouldn't need topping up. Other causes are a compressor…Why won't my power window go up?If you hear the motor whir but the glass doesn't move, the window regulator (the mechanism that lifts the glass) has usually broken. If you hear…
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