Cars · Lesson 13 of 15Beginner5 min read

Troubleshooting by Symptom

Good troubleshooting starts with noticing. What do you see, hear, smell and feel, and when does it happen? Those clues point to a system, and the system points to a fix. This finder walks you through the common ones.

Think like a technician

Notice the details. When does it happen: cold or warm, at a certain speed, when braking, when turning? Does it change with engine speed or with road speed?
Use your senses. Look for drips and smoke, listen for sounds, notice smells, feel for vibration and pulling.
Check the simple things first. Fuel in the tank, tire pressure, fluid levels, a tight gas cap, a blown fuse.
Read the codes and the warning lights. They’re clues, not answers (Lesson 5, and Read Dashboard Warning Lights).
Know when to stop. Some symptoms mean pull over now. The finder marks them.

Causes are listed roughly from the most common and simplest to check, to the less common. Your owner’s manual and a qualified technician have the final word for your car.

Drips by color

A puddle under the car is one of the best clues you’ll get. Slip a sheet of white cardboard under the engine overnight to see the color and where it lands.

Slide a sheet of white cardboard under the car overnight to see the color and where it drips. Source: Federal Trade Commission, Auto Repair Basics.

Smells, sounds and smoke (FTC and U.S. Navy training)
Clue	What it often means
Smell of burned toast	An electrical short and burning insulation
Smell of rotten eggs	A problem in the catalytic converter or other emission control parts
Thick, acrid smell	Burning oil
Gasoline smell after a failed start	A flooded engine; a strong fuel smell any other time needs checking
Sweet, steamy smell	A coolant leak
Squeal that follows engine speed	A loose or worn drive belt
Screech while moving	Brake wear indicators: time for brake service
Rumble	A bad exhaust pipe, converter or muffler; or a worn U-joint
Ping that follows engine speed	Fuel with lower octane than the car needs
Heavy rhythmic knock	Worn crankshaft or connecting rod bearings, or a loose torque converter
Random clunk	A loose shock absorber or other suspension part, or a loose exhaust pipe
Blue-gray smoke	Oil burning in the cylinders
Black smoke	Too much fuel or too little air
White smoke that doesn’t clear after the engine warms up	Possibly coolant getting into the cylinders

Before you pay for a repair

Check for open safety recalls: enter the 17-character VIN, found on the lower left of the windshield, at NHTSA’s recall site. Recall repairs are free at a dealer.
Ask for a written estimate that lists the condition to fix, the parts and the expected labor, and that says the shop will call you before doing extra work.
Look for technicians with ASE certification, but remember the FTC’s point: certification alone isn’t a guarantee of good or honest work.
Emission parts may still be under federal warranty (Lesson 5).

Check yourself

Tap an answer to check it, or open “Show the answer.”

You find a red, oily spot under the car. What is it most likely?
Show the answer
Transmission or power-steering fluid. A red oily spot points to transmission or power-steering fluid.
A sweet, steamy smell usually means what?
Show the answer
A coolant leak. Ethylene glycol coolant smells sweet when it leaks onto hot parts.
The engine clicks but won’t crank. What’s the simplest thing to check first?
Show the answer
The battery and its connections. Clicking with no crank is often a weak battery or a poor connection, the simplest things to check.
Which symptom means stop driving and get help?
Show the answer
The temperature gauge in the red and steam from the hood. An overheating engine can be seriously damaged; stop as soon as it’s safe.

Go deeper

Federal Trade Commission: Auto Repair Basics The FTC’s guide to symptoms and choosing a shop.
NHTSA: Check for Recalls Look up recalls with your VIN.
Being an Adult 101: Read Dashboard Warning Lights What each dashboard warning light means.
U.S. EPA: What to Do with the Check Engine Light (EPA420-F-00-041) What to do when the check engine light comes on.

Sources

The finder also draws on these sources:

I finished this lessonSaved on this device only.

A free course from Teddy Rook Book. It explains how cars work in general and follows U.S. sources; your owner’s manual and your vehicle’s service information are the final word for your car, along with state and local rules.