Toyota 2.7L Engine with Excessive Blow-by

I have a 2004 Tacoma with a 2.7 L engine and 45k miles. When I take the oil fill cap off while the engine is running (hot or cold), air blows out. So much blows out that an oil mist sprays out and I can feel the air (and droplets of oil) from 2’ above the hole. The engine runs smooth with no misses. I replaced the PVC valve and did a compression check (+/- 180 psi for all 4 cylinders and the plugs looked normal). With good compression I assume the rings are good so where is all the blow-by coming from? Does anyone else have a 2.7 L Toyota that does this.

Thanks in advance for any help!

Just a wild guess but if you aren’t losing oil, there’s nothing wrong. Put the cap back on and step away from the vehicle.

My 2.4 L 22R engine did the same thing. That engine lasted past 325K miles. I would not worry. Blow-by is a natural by-product of the engine’s operation. And, this amount of blow-by is not abnormal. I had noticed that my Toyota Supra and Mazda Protege also do it.

Hint, don’t open the oil fill cap with the engine running.

A 4 cylinder engine does a lot of breathing as the pistons move up and down. A better test of blowby is to put your hand over the oil fill hole and pinch off or block the fresh air hose going to the air cleaner box and see if you can feel a vacuum build up. Also look into the fresh air hose to see if there are signs of oil being blown out and check the air box for oil being blown there. If you get a vacuum and you see no oil being blown out of the crankcase fresh air system, don’t worry about what you noticed. If you don’t get a vacuum in the crankcase inspect the PCV valve and hose to make sure the crankcase is getting adequate ventilation.

Blowby is normal in all engines. In modern engines the system is “closed”, not exposed to the outside world, so some pressure can build in the crankcase, even though the PCV system ingests fumes as a normal part of operation. It takes a small amount of difference in pressure to achieve the effect you’re describing.

You’ve done lal the prudent things. The effect you describe is normal. The car sounds healthy. Happy motoring.

Blowby isn’t oil coming out of when you remove the oil filler cap. You should leave that on while the truck is running. Blowby happens when there is oil on the air filter or in the air filter housing. When that heppens, worry.