Symptom checker
Pick a sound, smell, feeling or leak and see the likely causes.
This narrows things down; it is not a diagnosis. If the car feels unsafe, stop and call for help.
All symptoms as a list
- High-pitched squeal when you brake (Fix soon): Brake pad wear indicator touching the disc; Glazed or low-quality pads; Moisture or light rust (stops after a few brakes). Read the full answer
- Grinding or scraping when you brake (Stop driving now): Pads worn down to the metal backing; A stone stuck between pad and disc; Damaged or worn discs. Read the full answer
- Clicking when you turn the key, but the engine won't turn over (Safe to monitor): Flat or weak battery (rapid clicking); Loose or corroded battery terminals; Faulty starter motor (single click). Read the full answer
- Squeal from the engine at start-up or when turning the wheel (Fix soon): Worn or loose drive belt; Worn belt tensioner or pulley; Low power steering fluid (older hydraulic systems).
- Humming or droning that gets louder as you speed up (Fix soon): Worn wheel bearing; Uneven tire wear; Tire tread pattern noise.
- A sweet, syrupy smell (Fix soon): Coolant (antifreeze) leaking onto hot engine parts; Leaking heater core (smell inside the car, misty windscreen). Read the full answer
- A smell of burning oil (Fix soon): Oil leaking onto the exhaust; Oil spilled during a recent oil change; Leaking valve cover gasket. Read the full answer
- Burning plastic or an electrical smell (Stop driving now): Overheating wiring or a short circuit; A failing electrical component or blower motor. Read the full answer
- A hot, acrid smell near one wheel (Fix soon): Sticking brake caliper; Handbrake left partly on; Hard braking down a long hill. Read the full answer
- A rotten-egg (sulphur) smell (Fix soon): Failing catalytic converter; Engine running too rich (check engine light often on). Read the full answer
- A strong smell of raw fuel (Stop driving now): Fuel leak from a line, injector or the tank; Loose or damaged fuel cap (a faint smell only).
- Steering wheel or pedal shakes when you brake (Fix soon): Uneven brake discs; Wheel nuts tightened unevenly; Worn suspension parts. Read the full answer
- The brake pedal feels soft, spongy or sinks (Stop driving now): Air or water in the brake fluid; Brake fluid leak; Failing master cylinder. Read the full answer
- The car pulls to one side when you brake (Fix soon): Sticking caliper; Unevenly worn or contaminated pads; Uneven tire pressures. Read the full answer
- The temperature gauge is high or there's steam from the bonnet (Stop driving now): Low coolant from a leak; Failed cooling fan; Stuck thermostat or failed water pump. Read the full answer
- Vibration through the steering wheel at higher speeds (Fix soon): Wheels out of balance; A damaged or bulging tire; Bent wheel. Read the full answer
- Clear, odourless water under the front of the car (Safe to monitor): Normal air-conditioning condensation, especially on warm days. Read the full answer
- A green, pink, orange or blue puddle that smells sweet (Fix soon): Coolant leak from a hose, the radiator or the water pump. Read the full answer
- A brown or black oily patch (Fix soon): Engine oil leak (sump plug, oil filter, gaskets). Read the full answer
- A red or reddish-brown fluid (Fix soon): Automatic transmission fluid; Power steering fluid (older cars).
- A clear to yellow-brown slippery fluid near a wheel (Stop driving now): Brake fluid leak. Read the full answer
- Nothing happens and the dashboard is dim or dark (Safe to monitor): Flat battery; Loose or corroded battery terminals; Key fob battery flat (push-button cars). Read the full answer
- The engine turns over but won't start (Safe to monitor): Out of fuel or a failed fuel pump; Immobiliser not recognising the key; Ignition or sensor fault. Read the full answer
- You hear clicking but the engine doesn't turn (Safe to monitor): Weak battery; Starter motor or solenoid fault. Read the full answer