Index
Diagnose by symptom
Start with what the car is doing — the noise, the light, the smell, the feel. Each guide gives you the safe-to-drive verdict first, then the causes ranked by likelihood with honest cost bands.
Noises
StopGrinding when brakingA grinding noise when you brake usually means the pads are gone and metal is cutting metal.SoonBrakes squealingSquealing brakes usually mean the wear indicator has reached the rotor — a deliberate….SoonSqueal on startupA high-pitched squeal at cold start or under load is the serpentine belt slipping.StopEngine knockingA deep knock that speeds up with the engine can be bearing failure — minutes matter.SoonClunk over bumpsA clunk or knock over bumps is a worn suspension joint or link letting parts move that….SoonHumming rises with speedA hum that tracks road speed and changes when you weave is a wheel bearing; steady drone….
Warning lights
StopCheck engine light flashingA flashing check engine light means an active misfire is dumping raw fuel into the….SoonCheck engine light steadyA steady check engine light means a fault is stored — the code turns guessing into a….StopOil pressure light onThe red oil can light means oil pressure has dropped below survival levels — bearings….SoonBattery light onThe battery light means the alternator stopped charging — the car is running down its….
Smoke & smells
SoonWhite exhaust smokeThin white vapor on cold mornings is normal condensation.SoonBlue exhaust smokeBlue-tinged exhaust smoke means oil is reaching the combustion chambers.SoonBlack exhaust smokeBlack exhaust smoke means the engine is running rich — burning more fuel than the air….SoonSweet smellA sweet, syrupy smell means coolant is leaking — and if it's inside the cabin, the….SoonRotten egg smellA sulfur smell from the exhaust means the catalytic converter is struggling — often….StopBurning smellBurning rubber, hot oil, and burning plastic smells each point at different failures —….
Driving feel
SoonShaking at highway speedVibration that appears at 55–70 mph and fades either side is classic wheel imbalance.SoonShakes when brakingA steering wheel that pulses under braking points at uneven brake rotors.SoonPulls to one sideA car that drifts or pulls left or right — the causes in the order they're actually….StopBrake pedal soft or sinkingA soft or sinking brake pedal means the hydraulic system is not holding pressure.SoonTransmission slippingSlipping, flaring RPM, or harsh shifts — check the transmission fluid before believing….SoonRough idle or stallingAn engine that shakes at idle or stalls at stops has an air, fuel, or spark problem that….
Won't start
SoonWon't start — clickingRapid clicking usually means a weak battery; one loud clunk points at the starter.SoonWon't start — silenceTotal silence when you turn the key means the start signal never reached the starter.
Leaks & overheating
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Describe what it’s doing in your own words and the symptom checker gives you a safe-to-drive verdict, ranked causes with costs, and notes to take to the shop — free, no sign-up.
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