The Reasons and Solutions for Smoke from Oil Cap

Do you see the engine fume when opening the oil filler cap? Smoke from oil cap is not good news for your car and its engine. What does it mean exactly? Well, it depends on the amount of smoke. A small amount is nothing serious but too much smoke is highly concerning.

How To Test the Smoke from Oil Cap?

You can easily find out whether the smoke coming from oil cap is a fatal sign or not. Start the engine and let the car idle for some time. Loosen the oil cap slowly and then remove it completely. If there is only a small amount of fume blowing out of the motor, you have nothing to worry about.

smoke coming from oil cap
You have to remove the oil cap for examination.

However, lots of fumes coming out with pressure is not a good sign. You should immediately take the vehicle to a servicing shop if the vapor seems to contain contaminated fume too.

Remember not to open the cap when the engine is hot. Also, close the tank with the cap when you are done. Clean up if there is any oil residue.

Watch more:

The Reasons for Engine Emitting Smoke from Oil Cap

There could be two possible reasons for smoke coming from oil cap:

  • Hot fuel bypasses worn valve stem seals and rings
  • When the fuel bypasses worn rings and valve stem seals

The smooth operation of the engine components relies on the specific amount of tolerances between them. The oil has to flow to all the parts to keep them moving without friction. Proper oil flow does not let the machinery lock or seize.

Over time, the components start showing signs of wear and the seals become thin. As a result, some of the games between these machines become too much wider for the oil to leak someplace where it should not be such as the combustion chamber. When the fuel drips through the piston rings and valves and gets into the combustion chamber, it turns into smoke with each firing shot of the fuel-air mix. The speedier you drive the car, the more will be the amount of oil leaking and smoke production.

When the engine is running and you open the oil filler cap, the steam will blow out because during operation the engine will generate steam, so on the new engine cover there is a 1-way steam valve to support the brake. In case the steam is ejected and there is no white or blue smoke, the engine is working fine, on the contrary, if there is blue or white smoke, it is a big possibility that the engine has damaged piston rings and then we should replace or repair it. 

In addition, your oil cap may be tight enough to create the pressure in the crankcase normally handled by a PVC system. In this case, defective valve seals are a candidate for the smoke from the oil cap. If faulty valve seals are the cause of the problem, they may require professional repairs. 

Read more:

How To Solve The Problem Of Smoke From Oil Cap?

You have to check the condition of the stem valves and piston rings and change them if one or both of them are damaged or worn out. The best solution is to change both parts because the older parts won’t be able to keep up with the pressure created by the newly replaced component.

smoke from oil cap
You have to change all the related parts.

For example, changing only the stem valves will keep the pressure contained where it should be. However, the old rings won’t be able to show the same strength and let the extra pressure to bypass through. The opposite will happen when you change the rings but keep the old valves.

These temporary fixes will only drain the money. If your car releases a huge amount of smoke with contaminated fume from the oil gap, change all the related components. You can also go for a used engine that still has many miles left on it.

Final Thoughts

To wrap up this topic, we want to affirm that if you notice some smoke emitted from the oil cap, it can be a normal situation, however, you should observe carefully the color and smell of smoke. If it’s thick and has a strange smell, the problem can come from the combustion chamber. Otherwise, you should check careful other parts:

  • Check piston rings
  • Inspect the valve stem 

To ensure safety, you should get an appointment with a trusted mechanic as soon as possible.