# Air blowing when the oil cap is taken off?



## robzero (Nov 12, 2006)

When I take the oil cap off of my engine, I notice a bit of air blowing out. Is anything wrong with this?

I've been told by some guy that it's a sure sign the engine to going to blow soon, but I'm having an extremely hard time believing that. Keep in mind this guy was looking at my car with intent to buy, so I'm thinking he's trying to bs a low price out of me.


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## mrgoose (Sep 13, 2006)

This doesn't seem strange to me. The crankcase ought to have positive pressure, which is partially alleviated by the PCV system. If you have a clogged/malfunctioning PCV valve, the crankcase pressure could be too high and you should replace your PCV valve (like a $5 part, easy to replace). However, even with the PCV system operating normally I would still expect a modest positive pressure in the crankcase, which would cause the bit of air coming out with the oil cap removed. If you haven't replaced your PCV valve in a couple of years or more I would do so, but otherwise I don't think I would worry. More typical signs that your engine might be in trouble are things like overheating, abnormal sounds, check engine light on, sudden large drop in performance etc.

By the way, if you don't already know, PCV stands for Positive Crankcase Ventilation. You can read all about it here: 
Engine: Crankcase Ventilation


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## HATEnFATE (Dec 24, 2002)

He's trying REAL hard to bs you too. tell him to go hump a tree and that you know what your engine is supposed to be doing.


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## R3DN1CK (Jun 14, 2007)

my car does it too. the car is a dohc. everytime the cam cycles the lifter pots go up and down. it's going to make the air move.


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