Symptoms
Car problems, by symptom
Start from what you hear, feel or see. Each page lists the likely causes, most common first, the checks you can make safely yourself and whether it is safe to keep driving.
Noises
- What causes a grinding noise when braking? A grinding noise when you brake usually means the brake pads have worn through their friction material, so their steel backing plates are scraping the discs.
- What causes a knocking noise over bumps? A knocking or clunking noise over bumps usually comes from a worn joint in the front suspension.
- Why are my brakes squeaking? Brakes squeak when the pads and disc vibrate at a high pitch as they rub.
- Why does my car click when turning? A clicking noise when you turn, loudest on full lock as you pull away, is usually a worn outer CV joint on a front driveshaft, most often after its boot has split.
- Why does my car make a noise when I press the clutch? A whirr, squeal or chirp that starts when you press the clutch pedal is usually a worn release bearing (US: throw-out bearing), which works only while the pedal is down.
- Why is my car humming when I drive? A humming noise that rises with road speed is usually a worn wheel bearing, especially if it changes as you go round a bend.
Shaking and vibration
- Why does my steering wheel shake when braking? A steering wheel that shakes when you brake usually means the front brake discs have worn unevenly, which is often called warped.
Pedal feel
- How can you tell if a clutch is slipping? A slipping clutch lets the engine's revs rise without the car speeding up to match, most clearly when you accelerate hard in a high gear or climb a hill.
- What causes a spongy brake pedal? A spongy or soft brake pedal usually means air in the brake fluid, which compresses where fluid does not.
- Why is my clutch pedal stuck to the floor? A clutch pedal that sinks to the floor or stays there is nearly always a hydraulic fault: a fluid leak, air in the line or a failed seal in the master or slave cylinder.
Steering and pulling
- Why does my car pull to one side when braking? A car that pulls to one side when braking usually has a brake that grips harder on one side than the other.
Gear changes
- Why does my car jump out of gear? A manual gearbox jumps out of gear when the sleeve locking the gear to its shaft is pushed back to neutral.
- Why does my gearbox grind when I change gear? A gearbox grinds when the gear you select is still turning at a different speed from the shaft it is being locked to.
Tyre wear
- What causes uneven tyre wear? Uneven tyre wear usually means the wheel alignment is out, the tyre pressures are wrong or a suspension part is worn, and the pattern points to which.
See where each part sits
Every part these pages mention is in the app in 3D: tap it for what it does and how it fails.
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