White smoke from exhaust, what it means and when it’s bad

White smoke coming from the exhaust doesn’t usually indicate a head gasket problem

White smoke from exhaust on cold startup is usually not a problem

When you start a cold engine, the computer commands a rich fuel mixture. The exhaust produced from a cold engine and rich fuel mixture produces a lot of hot water vapor from the exhaust. As soon as that hot water vapor his the cold air, it condenses, forming thin white smoke. It’s not really smoke. In fact, it like like a very thin mist of white vapor.

If the white smoke from the exhaust goes away as the engine heats up, it is perfectly normal and nothing to worry about.

Thick white smoke that doesn’t go away after the engine heats up is different

If engine coolant gets into the combustion chamber through a breach in the head gasket, the burned coolant can create a cloud of white smoke from the exhaust that doesn’t get much better as the engine heats up. You will also notice a low coolant level in the coolant reservoir under the hood. This is serious and should be checked by a shop ASAP. It will not get better on its own and can get much worse and cost a lot more if you ignore the symptoms.

Thick white smoke that doesn’t go away as the engine heats up is a symptom of a bad head gasket. Get it checked out ASAP.

©, 2023 Rick Muscoplat