White Smoke From Your Exhaust: How To Diagnose and Fix It

When it’s thick and heavy, you have a major problem.

Light white smoke comes out of a car's exhaust pipe.
Depositphotos

The Drive and its partners may earn a commission if you purchase a product through one of our links. Read more

As a general rule of automotive ownership, you never want to see your car smoking. Flames from the exhaust, maybe. But smoke? That’s a hard no. Regardless of the color, smoke is an abnormality and suggests something is wrong.

Fleeting condensation aside, especially during colder months, thick white smoke is a sign of a major issue that needs to be addressed immediately. Ignoring the smoke could, at worst, lead to a blown engine. 

To understand why your car is smoking and why the smoke is the color it is, you need to understand the basics of how a car works. Then, and only then, can we diagnose what’s the issue. The Drive’s encyclopedic informational team can help with that in terms and steps everybody can learn. Let’s get to it.

What Are Exhaust Emissions? 

The exhaust fumes that come out of the tailpipe of your vehicle are the direct byproducts of the combustion process happening in the engine. A spark lights a mixture of gasoline and air, and the resulting gases are funneled down the exhaust system. They pass through a catalytic converter to reduce harmful emissions and through the muffler to reduce noise. 

What Do Exhaust Emissions Normally Look Like? 

Under normal conditions, you probably won’t see the exhaust coming out of your tailpipe. As mentioned in the introduction, you might occasionally see a light white color, which is just water vapor. It’s important to understand that this is very different from the thick white smoke that brought you to us.

Why Does My Car Emit White Smoke From The Exhaust On Startup?

You know how people stranded on deserted islands send bonfire smoke signals to passing plans and ships? That’s what’s happening when you see white, black, or blue smoke coming from your exhaust pipe. Your car is sending out a distress signal begging for help.

White smoke coming out of your exhaust suggests that coolant or water has inadvertently entered the combustion chamber. When it’s burned within the block, it produces thick white smoke that exits through the exhaust. No bueno.

Exhaust fumes trail from an exhaust pipe.
Depositphotos

Much can be learned from watching the exhaust.

What Causes Coolant Or Water To Enter The Combustion Chamber?

Thick white smoke coming out of the exhaust typically indicates a blown head gasket, a crack in the head, or a crack in the engine block. Cracks and bad gaskets allow the fluid to travel to places it shouldn’t be. If it travels, then the problems begin.

What Should I Do If I See White Smoke Coming From My Exhaust?

Most importantly, you should not continue to run the car. If your engine has a gasket failure or a crack, it could lead to further contamination or overheating, which essentially means, “Goodbye, engine.”

If you want further proof that you’re having an issue with coolant leaking within your block, you have two options. First, you can check the coolant level. If you notice the level is low and do not see coolant leaking anywhere else, it supports the theory that you have a head gasket leak or crack. Furthermore, you can buy an engine block leak detector kit that uses chemistry to detect contamination in your coolant.

Unfortunately, once it’s set in that you have a blown head gasket, a cracked cylinder head, or a cracked engine block, it’s time to accept that you have a major repair ahead of you. The only way to confirm these issues is by removing half the engine and getting to the block. 

Where you go from here is up to you. Because this is one of the biggest car repairs one can encounter, we do not recommend amateurs without the proper tools to tackle this task in their own garages. Take it to your trusted mechanic and discuss whether or not a repair is worth it, depending on the value of the vehicle. You can either rebuild the engine, replace the engine, or buy a new car. For more information, visit The Drive’s guide, How To Deal With a Blown Head Gasket.

However, if you’re comfortable with the project, use a proper service manual, make a plan, and make sure you have the correct tools. Take your time, don’t cut corners, and don’t forget to label everything when you’re taking it all out.

An exhaust tailpipe spews vapor on a cold day.
Depositphotos

A normal exhaust on a cold day might show some light white vapor.

Sometimes You Need a Certified Mechanic

"As much as The Drive loves to put the "you" in do-it-yourself, we know that not everyone has the proper tools, a safe workspace, the spare time, or the confidence to tackle major automotive repairs. Sometimes, you just need quality repair work performed by professionals you can trust like our partners, the certified mechanics at Goodyear Tire & Service

FAQs About White Smoke Coming From The Exhaust

You have the questions, The Drive has the answers!

Q. So Can Low Oil Cause White Smoke?

A. No, it cannot. Unrelated to the fluid’s level, if oil does make it into the combustion chamber, you could see blue-tinted smoke coming from your exhaust.

Q. Ok, But Can Bad Spark Plugs Cause White Smoke From The Exhaust?

A. No, these two issues are unrelated.

Q. Then Why Is There Blue Smoke Coming From My Exhaust?

A. That’s a completely different issue, sometimes the whitish smoke that comes out of your exhaust is tinted blue. This suggests your engine is burning oil. When oil burns, it produces bluish smoke. 

Q. Is Burning Oil Bad?

A. Is your engine a two-stroke dirtbike?

Q. No.

A. Then yeah, it’s bad.