Six Causes of Smoke from Under the Hood: What To Do?

Are you a driver and have ever seen smoke from the underside of your car? This condition is scary and alarming, especially if you don’t know what is causing it. It is unusual for white smoke to come from your engine.

The engine's causes are discussed and possible solutions offered. A repair can be estimated at a cost that you might not have to pay.

Your combustion engine produces water vapor and carbon dioxide when it is operating as it should. The exhaust system channels this out and it is almost always unnoticed. It can also start to burn other things if the engine is not running properly. 

A form of contamination is indicated by white smoke. The engine burns something other than fuel and air. 

An external coolant, or oil, leak is the most frequent reason white smoke is seen from engines. An overheating engine could cause an external coolant leak, as the heat pushes coolant from the system to the engine bay.

Here’s a more detailed list of why there is white smoke coming from your engine:

How can white smoke be produced from an engine?

1. External Coolant Leak

White smoke coming from your engine bay could be due to an internal coolant leak, or overheating. If coolant is in direct contact with hot parts, it can cause white smoke to form.

Bad gaskets and cracked coolant hoses are two common causes of coolant leaks. To find out more about how to spot a coolant leakage, please visit this coolant leaks article.

Overheating can result in white smoke coming from the engine bay. This is because the coolant has emitted from the coolant systems. If the smoke is coming from the exhaust and not from the engine bay, let’s continue!

Reported: 9 Reasons Your Car's Engine Heats Up

2. Head Gasket

If the head gasket fails, coolant may leak into either the engine compartment or the exhaust pipe. The leak may be visible from the outside of your exhaust pipe if it's serious. But these issues often go unnoticed. 

It will still produce white smoke from the engine. Overheating can lead to engine damage. It is one of the most expensive repairs, but it is essential if your engine is to be saved. 

3. Broken Cylinder Head

If a head cracks in cylinder heads, coolant could leak into the chamber. The coolant will react with fuel to create the same smoke as a blown gasket.

As coolant is seeping into the engine, it can’t do its job, leaving your engine at risk for overheating. To check if coolant or oil are mixed, you can inspect the reservoirs. 

4. Defective Fuel Injector

Injectors ensure that fuel and oxygen are mixed together in the proper amount for combustion. The modern motors are extremely calibrated in order to make sure that the mixture does not change.

However, if the injector isn’t working right, the mixture might receive too much fuel. Because this fuel won’t be able to burn correctly, you will notice white or grey smoke coming from the exhaust. 

5. Poor Diesel Injector Pump Timing

You can also have trouble with your diesel engine if the mixture isn’t just right. It will behave just like an ailing fuel injector in a gasoline engine if the timing of your injector pump is not correct.

A mixture that is too fuelled can result from bad timing. It will eventually burn off, resulting in white smoke coming from your engine. 

6. Seals and valves that leak

Many seals and valves make up the engine. They all need to do their jobs properly for everything else to work. Oil can leak from a piston valve seal or ring if it becomes damaged. 

The burnt oil is more blue than the smoke, but it can easily be mistaken for white smoke. The oil will look whiter if there is less leakage, but eventually it will turn bluer. 

3 Different types of white smoke from engines

1. Vapor Thin
2. Sweet-Smelling Pipe
3. Smoke in Normal White

Vapor Thin

As part of its exhaust, your car will typically produce some vapor. If you aren’t used to seeing it or you start your vehicle on a cold day, you might be more alarmed. 

Exhaust steam that is produced when temperatures drop can appear darker and sometimes mistakenly be called smoke. You don't have to worry if the exhaust steam disappears rapidly. 

Sweet-Smelling Pipe

If the smoke appears thick, it is likely that there has been a coolant leak. Because coolant has a sweet smell, animals will also be attracted by it. 

Coolant can also be mixed with fuel to create white smoke. It’s also going to produce a distinct sweet smell that is unlike any other automotive fluid. A cracked cylinder or head gasket could lead to this problem, and both are expensive repairs. 

Normal White Smoke

If you notice white smoke coming from the engine, but you don’t smell anything unique, it could be caused by condensation in the exhaust. The exhaust can form just like water vapour, particularly if it is new to the vehicle.

Imagine dew on the grass. It's the exact same scenario, except that it is in your car exhaust. This will cause the smoke to quickly exhale. You should have your engine checked if the smoke continues to persist. 

Engine Smoke Repair Prices

According to the cause, cost of repairing white smoke will vary. As we’ve illustrated, there are several conditions that could occur. For something as simple as a bad gasket replacement will cost less than $150. Labor included. 

The cost of all other repairs can be quite high. A leaking seal or valve could run you anywhere between $50 and $1,000. The cost of a broken pump or fuel injector could be as high as $2,000 What’s most serious is a blown head gasket or the cracked cylinder, which isn’t just costly, but also difficult to repair. These problems can cost you up to $2,500 depending on the car that you have. 

If you are seeing white smoke from your engine you should get it fixed immediately. If you don't, the engine will suffer severe damage and may need to be replaced completely.