Car leaking fluid? Identify it by colour, smell and position
Put a sheet of card under the car overnight, then look at the colour, the feel and where the drip lands. Brown or black and oily is usually engine oil. Green, pink or orange and sweet-smelling is coolant. Clear water under the front footwell is normally air-conditioning condensation, which is nothing to worry about.
Two leaks mean don't drive: a slippery fluid near a wheel can be brake fluid, and a smell of fuel is a fire risk.
Free interactive diagnosis
What does it look like, and where is it?
Is it safe to keep driving?
For a typical car with each symptom. These are general guidance, not a diagnosis — if you're unsure, don't drive it.
- Car leaking oil (brown or black)Drive carefully
- Car leaking coolant (green, pink or orange)Drive carefully
- Red fluid leakingDrive carefully
- Car leaking waterUsually OK to drive
- Fluid leaking near a wheelDon't drive
- Smell of fuel or a fuel leakDon't drive
- Blue, watery leakUsually OK to drive
Car leaking oil (brown or black)
Drive carefully — book it in
You can drive gently, but get it looked at within days rather than weeks. Left alone it will get worse, less safe or more expensive.
Likely causes
- Engine or gearbox oil leakMost likely
Dark brown drips under the engine, an oily underside, and a burning smell if it's dripping onto the exhaust.
If it's this: get it checked soon.
- Automatic gearbox or power steering fluid leakLikely
Red or pink oily fluid, a whine when steering, or the gearbox slipping.
If it's this: get it checked soon.
What to do next
Check the oil level today and top it up if needed. A slow leak is a nuisance; a fast one can empty the engine.
Car leaking coolant (green, pink or orange)
Drive carefully — book it in
You can drive gently, but get it looked at within days rather than weeks. Left alone it will get worse, less safe or more expensive.
Likely causes
- Coolant leak (hose, radiator or water pump)Most likely
The coolant is below MIN when the engine is cold, there's a sweet smell, and a puddle under the front of the car.
If it's this: get it checked soon.
- Head gasketPossible
Thick white sweet-smelling smoke, coolant disappearing with no visible leak, and bubbles in the expansion tank with the engine running.
If it's this: don't drive.
What to do next
Check the coolant level when the engine is cold and top it up. Watch the temperature gauge — if it climbs, stop.
Red fluid leaking
Drive carefully — book it in
You can drive gently, but get it looked at within days rather than weeks. Left alone it will get worse, less safe or more expensive.
Likely causes
- Automatic gearbox or power steering fluid leakMost likely
Red or pink oily fluid, a whine when steering, or the gearbox slipping.
If it's this: get it checked soon.
- Engine or gearbox oil leakLikely
Dark brown drips under the engine, an oily underside, and a burning smell if it's dripping onto the exhaust.
If it's this: get it checked soon.
What to do next
Check the power steering fluid (if it has one) and get the gearbox level checked — an automatic gearbox run low on fluid gets damaged quickly.
Car leaking water
Usually fine to drive — get it checked when convenient
Usually a nuisance rather than a danger, and unlikely to strand you or cause other damage in the meantime. Get it checked when it's convenient — sooner if it gets worse or anything else changes.
Likely causes
- Air-conditioning condensationMost likely
Clear water with no smell under the front of the car after using the air-con. Normal.
If it's this: not urgent.
- Coolant leak (hose, radiator or water pump)Possible
The coolant is below MIN when the engine is cold, there's a sweet smell, and a puddle under the front of the car.
If it's this: get it checked soon.
What to do next
Almost certainly air-con condensation, which is normal. If it smells sweet or feels slippery, it isn't water.
Fluid leaking near a wheel
Stop — don't drive it
If you're driving, pull over when it's safe and switch off. Don't drive it again until it's been checked — have it recovered if you need to. Carrying on risks the engine, your brakes or your steering, and recovery costs less than the damage.
Likely causes
- Leaking brake hose or corroded brake pipeMost likely
A spongy pedal, the brake fluid level dropping, and a wet patch on the inside of a wheel.
If it's this: don't drive.
- Worn or leaking shock absorberLikely
A bouncy, floaty ride, oil wetting the shock absorber body, and patchy wear across the tyre tread.
If it's this: get it checked soon.
What to do next
Brake fluid near a wheel means a leak in the braking system. Check the brake fluid reservoir and don't drive it until it's checked.
Smell of fuel or a fuel leak
Stop — don't drive it
If you're driving, pull over when it's safe and switch off. Don't drive it again until it's been checked — have it recovered if you need to. Carrying on risks the engine, your brakes or your steering, and recovery costs less than the damage.
Likely causes
- Fuel leakMost likely
A strong fuel smell or drips. Don't start the engine — a fuel leak is a fire risk.
If it's this: don't drive.
What to do next
Don't start the engine or smoke near it. A fuel leak is a fire risk — have it recovered to a garage.
Blue, watery leak
Usually fine to drive — get it checked when convenient
Usually a nuisance rather than a danger, and unlikely to strand you or cause other damage in the meantime. Get it checked when it's convenient — sooner if it gets worse or anything else changes.
Likely causes
- Screenwash bottle or pipe leakMost likely
Thin blue or pink fluid, and the washer bottle keeps emptying.
If it's this: not urgent.
What to do next
Screenwash. Harmless, but you'll want the bottle or pipe fixed before a dirty winter road.
A shortlist, not a diagnosis
The ranking is the one a mechanic would give over the counter for a typical car — nobody can road-test a car over the internet, and the real cause may not be listed. Add the registration in the checker above to have it checked against that car's MOT advisories, mileage and engine. Have the car checked by a qualified mechanic before relying on it, and if you're unsure whether it's safe, don't drive it.
Common questions
Is it normal for a car to leak water?
Yes, if it's clear, has no smell and drips under the front of the car after the air conditioning has been on — that's condensation. Water that smells sweet or is coloured is coolant, and water inside the car usually means a blocked drain or a failed seal.
Can I drive with an oil leak?
A slow seep, usually yes, as long as you check the level often and keep it topped up. A steady drip, a puddle, or oil landing on the exhaust (smoke or a burning smell) needs fixing within days — running low on oil destroys an engine.
What colour is brake fluid?
Clear to yellowish when new, darkening towards brown with age, and slippery to the touch. Any fluid near a wheel or on the inside of a tyre could be brake fluid — don't drive until it's been checked.
Related symptoms
Exhaust smoke
Smoke from the exhaust: what white, blue and black smoke mean
Brakes
Brake problems: squeaking, grinding, judder or a soft pedal
Other warning lights
Dashboard warning light on? What it means and what to do
All symptoms: Engine management light · Other warning lights · Won't start · Exhaust smoke · Running poorly · Brakes · Steering & vibration · Noises · Symptom checker