Why Is Smoke Coming Out Of Oil Filler Cap?

Smoke coming out of the oil filler cap is not a normal sight. It can be quite an eye opener, too, because it can indicate that there's something really wrong with your engine. We're here to help you figure out the root cause of the problem.

It's Normal For A Small Amount Of Smoke To Come Out

Oil cap smoke

First, we want to mention that if you see a small amount of smoke come out, chances are there's nothing wrong with your engine. These are just engine fumes escaping from the oil cap. This is especially true if you engine is cold when you observe the "smoke". It is probably just water vapor in this situation.

But how can you know for sure whether the smoke you're seeing is normal? Here's a little test you can try:

  1. Start your car and then let it idle for 1-3 minutes. Don't let the engine get too hot.
  2. Pop the hood and then carefully remove the oil filler cap.
  3. Observe the amount of smoke and/or fumes coming out.
  4. Turn off the engine and then put the filler cap back on. (If you accidentally spilled any oil residue on the engine, be sure to clean it up.)

How much smoke is there? If there's a minimal amount of smoke coming out, then you may not have anything to worry about. If the smoke blows out with pressure, then there's definitely something wrong.

The Culprit: Exhaust Leakage

Like smoke coming out of your tailpipe, you can attribute smoke coming out of the oil cap to exhaust.

The valve stem seals and piston rings degrade over time. When that happens, exhaust can bypass the worn valve stem seals and piston rings. When the valve stem seal is bad, the pistons push the exhaust out of the area that's supposed to be sealed. If you see smoke coming out of the oil filler cap, it means that the intake valve stem seals or piston rings are bad.

How To Fix This

The best way to fix this is to:

  • Check the valve stem seals and piston rings
  • Replace the valve stem seals and/or piston rings if necessary

Getting Replacement Parts At Wholesale Pricing

Toyota oil filler cap

If you need to replace the valve stem seals and/or piston rings, look no further than us. We carry genuine OEM Toyota parts at wholesale pricing. We also offer fast same-day shipping and no-hassle returns. Look up your Toyota model in the following catalogs to see if we have the right replacement parts for your car:

Do you need help finding the right parts for your car? We'll be happy to help!

Written by Jason Lancaster