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White Smoke From Semi Truck Exhaust? (9 Causes Explained!)

When using a semi truck or any other vehicle, seeing thick smoke coming out from the exhaust is a big no. It is a possible indication of a problem with the engine. If the smoke’s color is white, the most common reason is injector failure. 

Some people overlook that seeing white smoke is okay or less harmful. But it has similar concerns when seeing a black or a gray smoke from the exhaust.

So what should you do as soon as you see a cloud of white smoke coming out from your semi truck’s exhaust? First thing, you need to know the underlying causes of it.

Here’s a short summary of Why you will get White Smoke from a Semi-Truck Exhaust:

A semi-truck exhaust may emit white smoke due to damaged components such as injectors, crankshaft keyway, timing gear, cylinder liners, or fuel lines. Also, low cylinder compression and combustion of diesel fuel with water mixture could also cause white smoke to be discharged from a truck’s exhaust.

How much White Smoke from the Exhaust is Normal?

Even if you consider white smoke to indicate engine failure or issues, it is often not a sign of any trouble.

If there is only thin white smoke coming out of your semi truck’s exhaust, it can just result from the engine warming up, which is normal.

But if it is a thick burst of smoke, you should check and find out the cause regardless of the color.

Is White Smoke on Cold Start Normal?

If you see a cloud of white smoke coming from the exhaust of your semi truck, you should not conclude that there is an issue with its mechanisms yet.

Seeing white smoke on the exhaust during the winter and cold mornings is a possible everyday occurrence. So it’s mostly a regular thing.

It only looks thin and not that visible. It is also just a result of the engine warming up because of the cooler temperature in the environment. Thus, it is not a sign of any trouble.

However, if the white smoke happens on a warmer or typical day, it can be a sign that there are underlying issues with the engine of your semi truck.

Does White Smoke Always mean Blown Head Gasket?

There are many causes of white smoke from your semi truck’s exhaust. A cloud of white smoke may come from the coolant leaking into the cylinder, and it often happens when the head gasket is blown.

If you face the same issue, you need to check the head gasket right away and have it fixed before it gets worse.

Can Dirty Injectors Cause White Smoke?

Old fuel, carbon, and fuel residues are the common cause of why injectors get dirty, causing their filter baskets to clog.

If left unclean, the dirt and fuel residues inside will build up and prevent the fuel from flowing. 

Dirty injectors may cause several issues like increased fuel consumption and hard starting, including white smoke emissions.

Using a good-quality fuel injector cleaner can help lessen the dirt. You can also clean the outside of the engine so it does not accumulate more dirt.

Can a Fuel Injector Cleaner Cause White Smoke?

Some people have encountered white smoke after using a fuel injector cleaner. They thought that using it was the reason behind the appearance of the smoke.

The reality is that the fuel injector cleaner is not the leading cause of the white smoke. When applied correctly, you will not notice any smoke coming from the exhaust. 

But if the injector cleaner used has impurities such as moisture, it can be combustible once combined with the fuel injector cleaner and produce white smoke.

Can a Bad Fuel Filter Cause White Smoke?

If you have a wrong fuel filter, your semi-truck will have a hard time starting, vehicle stalling, failure in the fuel system component, and loud noises from the fuel pump.

Because a bad fuel filter makes the engine fail to work correctly, there is a tendency for it to cause white smoke.

The best thing you can do is replace the fuel filter to prevent possible failures using the semi-truck.

Can Low Fuel Cause White Smoke?

Some people think that having low fuel will eventually produce a cloud of white smoke from the exhaust of their semi truck.

The truth is, low fuel will not cause white smoke. 

Low fuel can still flow into the combustion chamber even if it is not at the same level as the fluid. But if it does, instead of white smoke, a cloud of blue smoke is most likely to appear from the exhaust.

But of course, always maintain the fuel level to avoid other common engine problems.

Can Water in Diesel Cause White Smoke?

Another common factor of white smoke coming out from the exhaust of a semi truck is the presence of water in diesel, which is a major red flag.

Water can cause white smoke that looks like a thick cloud when mixed with diesel. The engine can get compromised when there is water or coolant in the combustion chamber.

The cause of water getting in the diesel engine is if there are cracks in the cylinder head, engine block, or a blown gasket head.

When left unattended, it can cause significant damage to the engine. You may find it hard to run again.

The best thing you can do is have your engine diagnosed to prevent any other issues with your semi truck’s performance.

Can Too Much Oil Cause White Smoke From Exhaust?

Most people fill oil into their semi-trucks, especially for long voyages, thinking it will prevent them from frequently stopping for a refill. Unfortunately, it may not be as helpful as you think.

When overfilled with oil, you will notice a dense white smoke coming from the exhaust. The main reason is that the excess oil is possibly burning in the engine block.

Though sometimes other fluids such as antifreeze can be the reason for the thick, dense smoke coming out of the exhaust.

Can Misfires Cause White Smoke?

Misfiring results from unburnt fuel in the cylinder for those unfamiliar with the term. It happens during the combustion cycle of any vehicle, including the semi truck.

Most of the time, a misfire will cause black smoke. But if you see a white smoke instead, it is an indication that your semi truck’s engine has developing damage inside.

The damage may have caused the engine oil to seep into the cylinder and mix with fuel, which causes the white smoke to come out.

Can I Drive with White Smoke From the Exhaust?

While in the middle of a drive, it is normal for semi truck drivers to encounter a sudden stop due to seeing a cloud of white smoke coming out of the exhaust. And that is indeed a wise thing to do.

Stop and check the engine condition. As soon as you notice white smoke coming from the exhaust of your semi truck, it would help if you did not continue to run it in the meantime. 

If you continue doing so, it can lead to overheating and break the engine.

If the engine has a blown head gasket, a cracked engine block, or a broken cylinder head, have it checked by a skilled or veteran mechanic for a repair if you do not know exactly what to do.

You can discuss the best thing to do with your trusted mechanic for the engine. 

The options are to rebuild the engine, buy a new engine to replace the old one, or, worst-case scenario, buy a new semi-truck. 

Yes, that is how serious this problem is, so you need to take it seriously. Immediate action is the most important thing to prevent all these from happening.

How Do I Fix White Smoke From Exhaust?

White smoke is mainly caused by a cracked head gasket, which leaks, causing the coolant or water to seep into the cylinders.

To fix white smoke from your semi truck’s exhaust, you can replace the head gasket or undergo a repair treatment to seal any leaks inside.

If you do not take action immediately, you might need to spend a lot on the repair cost, depending on which are affected. The price may cost you around $75 to $200 and requires a lot of time to get fixed.