Smoke and smells
Sweet antifreeze smell: what it means and what to do
A sweet, syrup-like smell when you stop the car or turn on the heater usually means coolant is escaping and evaporating on hot parts. If you smell it inside the cabin or the windows fog up with a greasy film, it may be the heater core.
See a garage soonSmoke and smells
Reviewed by Daniel Morales, founder of Reprorace SL, on
Is it serious? Can I keep driving?
Carefully, and only as far as the garage. You can drive carefully to a shop if the engine temperature and the coolant level are fine. If the temperature rises, you see steam or the level drops fast, stop and switch the engine off. Air out the car: those vapors are not good to breathe.
A careful, general answer: only someone who inspects the car can say whether it is safe to drive. When in doubt, stop somewhere safe and call for assistance.
Most likely causes
- Leaking hose or clamp: drips onto the exhaust or the block and evaporates.
- Heater core: the smell comes through the vents and the windows fog up.
- Cap or expansion tank: steam escapes when the system is under pressure.
- Water pump: its seal drips at the front of the engine.
- Head gasket: if there is also white smoke and the level drops with no visible leak.
Listed from more to less common in general; on your car they may be different. A fault-code reading and a check at the garage confirm which one it is.
To understand it better: What does the engine thermostat do and what does P0128 mean? How often should you run diagnostics on your car?
Car system: Cooling
What you can check yourself
With the engine cold, check the level in the expansion tank.
Look for drips or colored crust on the hoses, the radiator and under the car.
Check whether the passenger floor mat is damp: that points to the heater core.
Notice whether the windows fog with a greasy film when the heater is on.
Safe checks only: with the engine off and cold whenever you look under the hood, without taking anything apart and without touching hot or moving parts.
How the ECO-LITE helps diagnose it
Plugged into the OBD socket, the ECO-LITE reads the fault codes of the control units that answer, with the freeze-frame data captured when the fault happened, and shows live data on your phone or computer. With your permission, your garage can see them remotely before you bring the car in.
What to look at here: live coolant temperature and level or temperature codes; the smell itself sets no code.
Frequently asked questions
Is coolant toxic?
Yes, the liquid is toxic if swallowed and its vapors are not good to breathe. Clean up spills and keep it away from children and pets.
Why do I only smell it when I stop?
Because without the airflow from driving, the vapor from a small leak builds up around the car.
Can I use a leak sealer?
It can be a temporary patch, but it can also clog passages. Better to find and fix the leak.
Keep reading
- Engine cooling: how it works and what fails
- Low coolant warning light on: what to do
- White smoke from the exhaust: what it means and what to do
- Car heater not blowing hot: what it could be
- Car symptoms: what they mean and what to do
- Check engine light on: what to do
- How to read and clear your car's fault codes
- OBD fault codes: what each one means