How to describe a car problem to a mechanic

Why the description matters

Intermittent problems are the ones that cost the most time. The car shudders on the highway, then behaves perfectly for the technician's ten-minute test drive. Whatever you can tell the shop about when and how it happens is the map they work from. A vague description tends to get a general check. A precise one gets the right test.

The Federal Trade Commission's guide to auto repair makes the same point from the other side. It says you can detect many common problems with your own senses (looking, listening, feeling and smelling), and it walks through what those clues usually mean.

Before you go: write it down

Keep a note on your phone for a week or two, and add to it every time the problem shows up.

• When. Cold start or warm engine? First drive of the day? After sitting for a few days?
• Speed and load. At idle, accelerating, cruising, braking, turning? At what speed, roughly?
• How often. Every time, once a week, only on long trips?
• Conditions. Hot or cold weather, rain, hills, a full load, towing?
• What changed. Did it start after a repair, a new set of tires, a pothole, a fill-up?
• Warning lights. Which ones, and did they stay on or go out? Our warning light guide explains the colors.
• Mileage. The odometer reading when it started, and now.

The mileage is the detail owners leave out most. In the complaints owners file with NHTSA for the vehicles on this site, only 49% state a mileage we can read. Your mechanic will want it, and so will anyone comparing your car against others.

Describe what you sense, not what you think it is

"I think it's the transmission" sends a shop down one path. "It hesitates for a second when I press the gas from a stop, then lurches" lets the technician decide. Give the symptom first. Add your guess afterward, if you have one.

The FTC's guide lists the kinds of clues that help, and the words to use for them.

Sounds. Name the sound and when it happens. The FTC distinguishes a squeal (shrill, usually tied to engine speed, often a loose or worn belt), a click, a screech (high-pitched and metallic while moving, often brake wear indicators), a rumble, a ping (metallic tapping with engine speed, often fuel with too low an octane rating) and a heavy knock (a rhythmic pounding that can mean worn crankshaft or connecting rod bearings). Say whether it follows engine speed or road speed. That one distinction narrows things a lot.

Smells. The FTC's list includes burned toast (often an electrical short, and a reason not to drive until it's diagnosed), rotten eggs (usually the catalytic converter or other emission parts), a thick acrid smell (burning oil), gasoline after a failed start, burning resin (overheated brakes or clutch) and a sweet, steamy smell (a coolant leak).

Leaks. Note the color of any drip under the car. According to the FTC, yellowish green, pastel blue or fluorescent orange points to antifreeze, dark brown or black oil to an engine oil leak, and red to transmission or power-steering fluid. A clear puddle is usually just condensation from the air conditioning.

Feel. Pulling to one side, vibration at a certain speed, a spongy brake pedal, steering that wanders. Say when it happens and whether it's getting worse.

Use the owners who went first

If your problem is common on your model, other owners have described it already. Look up your year, make and model here and find the matching symptom sheet. Each sheet lists the phrases owners use most, what got replaced and at what mileage, and whether a recall or NHTSA investigation covers that system.

Two cautions. A pattern on your model is a lead for the technician, not a diagnosis. And don't lead with "the internet says it's the rack." Offer it as context: "I've read this is a known issue on this model around 60,000 miles."

At the counter

• Ask for a written estimate. The FTC says it should name the condition to be repaired, the parts and the expected labor charge, and that you should get a signed copy.
• Ask to be called before extra work. The estimate should say the shop will contact you before going past a set amount of time or money. The FTC notes some states require that.
• Ask about diagnostic charges. Many shops charge for diagnosis, and the FTC suggests finding out whether you'll pay it if you get the work done elsewhere.
• Offer to ride along. If the problem only shows up in certain conditions, a short drive with the technician can help them catch it.

Ask them to check the simple things first

The FTC gives several examples. Loose wiring can make an alternator look defective. Corroded or loose battery terminals can make a battery look dead. What seems like a failed starter may be a dead battery or a poor connection. For transmission complaints, it says to make sure the technician checks simple items like a disconnected hose or plugged filter first, since transmission repairs are normally expensive.

When you pick it up

Ask for a completed repair order. The FTC says it should list each repair, the parts and what each cost, the labor charges, and the odometer reading when the car came in and when the work was finished. Ask for the old parts back, which some states require shops to provide.

Keep that paperwork. If the problem later turns into a safety recall, a repair order is what you'll need to claim your money back (our reimbursement guide explains how). If it's a safety problem, it also belongs in a complaint to NHTSA, and our complaint guide covers that.

If the fix doesn't hold

Go back to the same shop first, with your notes. If the answer isn't satisfying, the FTC suggests a second opinion for expensive or complicated repairs, and notes that shops doing diagnosis only (without selling the repair) may give a more objective view. For disputes, it points to the shop manager or owner first, then your state attorney general or local consumer protection office, then small claims court.