What Is The White Smoke Coming Out Of A Car Exhaust?

And why does it always seem to happen at the most inconvenient time?

Holly Large - Editorial Assistant

Holly Large

Holly Large - Editorial Assistant

Holly Large

Jr Copy Editor & Staff Writer

Holly is a graduate medical biochemist with an enthusiasm for making science interesting, fun and accessible.

Jr Copy Editor & Staff Writer

Fact Checked by Johannes Van Zijl

Johannes has a MSci in Neuroscience from King’s College London and serves as the Managing Director at IFLScience.

white exhaust fumes

No, it doesn't mean there's a mini version of Stars in Their Eyes happening inside the exhaust pipe.

Image credit: Ambartsumian Valery/

Cars are generally a convenient way to get us from A to B, but unfortunately, they’re also no stranger to going wrong from time to time. Sometimes it’s difficult to tell what the problem is, but there can be clues to look out for. One of these is white smoke coming from the exhaust – but what does it mean? 

Time matters

The first step to deciphering white exhaust smoke is taking note of how long it lasts. If it only pops up for a short while after starting up and the weather also happens to be wet, what you’re probably seeing is evaporation as the result of the car warming up.


However, if white smoke continues to come out of the exhaust, this is generally a sign that coolant is leaking into the car’s engine. That’s not great news, as coolant helps to stop your engine from overheating and eventually, packing up. 

And if coolant is leaking, that can be indicative of a bigger issue; it’s important to find out what’s causing the leak in case that could cause other problems. It’s like one big, inconvenient, and potentially quite expensive, puzzle.

Blown gasket

Coolant leaking can sometimes be the result of a failed or “blown” head gasket. Found between the cylinder head at the top of the engine and the block, this is the part of a car that stops coolant and oil from mixing together.

The head gasket can get damaged due to overheating, or sometimes due to sudden amounts of high pressure. This breaks the seal between oil and coolant and abracadabra – you’ve got white smoke.

Cracked cylinder head or block

Remember those other parts of the engine we mentioned, the cylinder head and the block (the main part of the engine)? Well, those are important in keeping coolant out of the engine too. Even if there’s not a problem with the gasket, the cylinder head is sealed in place with it, so if it’s cracked or deformed in anyway, that can also lead to leakage issues. 

Similarly, the main engine block holds all of the major parts of an engine together, so if there’s damage to it, coolant may be able to escape from somewhere and run riot.

All that being said, this information is just an indicator of what the issue could be. There are many different possibilities; leaky radiator caps or damaged radiator hoses can also create problems. It’s best to get an official diagnosis from a professional in order to get a car running both smoothly and safely once again.

All “explainer” articles are confirmed by fact checkers to be correct at time of publishing. Text, images, and links may be edited, removed, or added to at a later date to keep information current.


  • tag
  • cars,

  • engines,

  • exhaust fumes