Diesel Engine Is Blowing White Smoke – Explanation

Diesel Engine Is Blowing White Smoke – Explanation

Smoke coming out of your engine is always scary. You never know what could have gone wrong in your engine for it to be blowing off smoke.

One may feel stressed witnessing this. Unsurprisingly, there is never one cause behind your diesel engine blowing white smoke. The smoke may not be coming out of the engine more often than not.

Diesel Engine Is Blowing White Smoke

An underlying engine problem can be using the exhaust pipe to outlet the smoke. You may wonder, what does it mean when a diesel engine is blowing white smoke?

It may be due to various reasons, including a faulty injector, unburned fuel, antifreeze leakage, transmission fluid leakage, and many more.

Here are some reasons why your diesel engine may be blowing white smoke:

Unburned Fuel

A common situation in which a diesel engine can blow white smoke through the exhaust is unburned fuel. A strong odor characterizes this unburnt fuel.

Due to low compression in the engine, the piston rings may be worn, or the valves may be burnt. Due to this, they may allow unburned fuel to flow through.

As a result, the engine combustion may occur incompletely. Dirty nozzles may also cause unburned fuel to pass through.

It is because dirt in the nozzle may impact spray patterns. Another cause could be when the fuel is too excessive for the air in the cylinder.

Contaminated Fuel

When the fuel is contaminated, it can also cause white smoke to blow off from the exhaust. When the water is contaminated with fuel, it causes burning with steam in the cylinder, this emitting white smoke.

When condensation settles in a less than full fuel tank, fuel is contaminated by water. Water can also be picked from the bottom of fuel storage tanks when water seepage from under the ground enters fuel storage tanks.

Clogged Fuel Filter

Clogged fuel filters can lead to several problems, including engine problems such as stalling, engine misfires, and power and acceleration loss.

For this reason, you should replace a clogged fuel filter as soon as you can and clean the fuel tanks for any settled residue when you change the filter.

If your engine is blowing off white smoke via exhaust pipe, a common reason is a clogged fuel filter. Water and rust can contaminate fuel filters and eventually restrict fuel flow to the engine.

As a result, air and diesel flow into the combustion chamber. At the same time, a damaged filter fuel can contaminate the fuel itself.


After long periods of inactivity, it is normal for your car to blow off a bit of white smoke. It is because fuel droplets may freeze during long periods of leaving your car inactive.

However, the smoke should disappear once you drive your car for a while and the engine warms up. If the smoke persists, it could be an issue.

If your diesel engine blows off white smoke from the exhaust while starting the engine, the cause could be condensation.

In low temperatures and damp conditions, condensation can settle in various vehicle parts, such as the exhaust pipes and the mufflers.

The condensation evaporates and fuses with the exhaust gas when starting the engine. As a result, you may find your diesel engine blowing off white smoke.

Leak In The Coolant System

A leak in the coolant system would also be why your diesel engine is blowing white smoke.

A leak in the cooling system means that the liquid coolant can pass through the combustion chambers through cracked blocks or heads.

What Does It Mean When a Diesel Engine Is Blowing White Smoke

A bad injector sleeve usually causes it. A damaged head gasket could also cause the coolant to enter the cylinders.

A strong yet sweet smell usually characterizes a leaked coolant system. At the same time, you will notice that the radiator coolant levels keep dropping.

Furthermore, the loss of coolant could also cause your engine to heat up. It typically happens when the leak is through the cylinder head gasket.

These gaps enable the coolant to mix with the diesel in the combustion chamber. When the combustion chamber ignites, the coolant evaporates in thick white smoke.

If you think that the cause behind your diesel engine blowing off white smoke is a coolant leak, you should inspect your engine compartment.

It is dried coolant if you find some powdery green residue or green puddles under the engine.

Transmission Fluid Leak

Another reason your diesel engine is blowing off white smoke could be due to a transmission fluid leak.

Transmission fluid leak is characterized by the dripping of fluid from your vehicle that is red rather than green. Another indication is a strong, pungent odor as the burning of transmission fluid generates it.

It usually happens when a diaphragm valve of the modulators of the transmission case is damaged. Since these valves carry transmission fluid, the fluid may enter the intake system when they are damaged.

When there is a transmission leak, you will have to locate the leakage. When the cause is something as small as a loose seal or gasket, all you have to do is tighten it.

Other damaged parts responsible for transmission fluid leakage leading to diesel engines blowing off white smoke may have to be replaced.

Other Causes

Aside from these, several other less common causes may cause your diesel engine to blow off white smoke from the engine or the exhaust. Here are some of those listed:

  • Faulty Injection Timing
  • Damaged Crankshaft Keyway
  • Faulty Timing Gear
  • Damaged Rings or Cylinder Liners (white smoke from the engine with exhaust as outlet)
  • Damaged Fuel Lines

Other Kinds Of Smoke

If the smoke blowing from your diesel engine is not white, the cause is usually something other than these, so you should not assume these causes could be responsible.

Diesel engines often blow off black or blue smoke, which could be different. Here is why your engine may blow off black or blue smoke:

Black smoke usually occurs when unburnt fuel blows out of the combustion chamber and mixes with gases in the exhaust.

On the other hand, blue smoke usually occurs when the vehicle burns engine oil. It is characterized by excess emptying of oil.

Final thoughts

It can be somewhat dangerous if your diesel engine is blowing white smoke. In this situation, the intelligent thing to do is get to the root cause right away.

You can decide the best solution or take your car to a mechanic if needed.

The bottom line is that you should always know why your car is acting the way it is, whether it is because of unburned or contaminated fuel or a clogged fuel filter. Only then can you do justice to it.