djh781997

So I have a 2006 Accord 2.4 and I recently noticed that when I remove the oil fill cap while the engine is running, a lot of air comes out. It sounds like a second exhaust system coming out of the valve cover. Sounds like the valve cover has an aftermarket muffler. LOL There is no smoke coming out, just air. I am very experienced with engines and how they work so please do not tell me that this is blow by, PCV valve or plugged cat. I have not noticed any power loss, millage loss or change in how the car runs. The car has 140,000 miles on it and I service it religiously. If anyone has any ideas can you please help me out.

GoLowDrew

Why would you do that? Keep that cap on while the engine is running. Your car is fine.

djh781997

That is one of the tests I do on every car I check out/work on. Very fast and simple way to hear what the top end sounds like. No other car has ever done this. I have checked another 2.4 Accord and it does not do what mine does. I expressed in my post that I am VERY experienced with engines and I am looking for an experienced answer.

GoLowDrew

Ok, I was afraid that (newbies) would try this, and maybe have oil splash out. Carry on.

djh781997

Look pal, just because I am a noob on this site don't ever confuse me for being a noob all together. Ive been around engines a long time. This is not normal. Take your oil cap off and tell me what you hear. I guarantee you will not hear what I hear.

90sedan

Excessive crankcase pressure, what else would it be? Perform a cylinder leak down test to confirm.

You misread his posts, he wasn't calling you a noob, he was referring to other people on this site.

GoLowDrew

Don't get offended. You made it clear that you are an experienced person. My use of the word "newbie" was that there would be less experience people trying and experimenting. It was not calling you a newbie.

Do you want to start over? I can clean up this thread.

djh781997

OK, I'm sorry for the quick come back. I have been trying to find the answer to this for quite some time and all i have been getting is people giving me lame so called fixes. Gets a little frustrating. The best way to describe it is exhaust coming out of the valve cover. I hear all 4 Cly, not just one or two.That leads me to believe it is not a valve prob.

LPED

A engine in good shape will have a vacuum on oil cap from PVC system. If your feeling pressure it probably blowby or a PVC issue . you are getting excessive crankcase pressure as other post mentions. you need to check things out .

PS: the car could run fine and have smooth engine if all cylinders have same leakage, so you can't go by that .
Check leak down cylinder test and if PCV system is working ok .Also make sure hose from valve cover to rubber intake hose is clear all the way through .

djh781997

Comp. test. Good
Leak down. Good
PCV. Good
EGR. Good
Exhaust flow. Good

LPED

you say PVC is all good. So do you feel suction on the metal line going to intake rubber intake hose .meaning remove the end of metal pipe going into the large intake hose and while engine is running at idle you feel suction from the metal line that goes to valve cover (with oil cap on ) ?
If you loosen oil cap and rest it over opening does it pulsate up and down over opening with each cylinder firing .
Some engines are much louder with cap off .

Targa250R

So, what exactly is the problem here? I'm not really seeing anything to be concerned about, so I have no idea why you're asking about this.

hayabusa160

this is 100% normal. if you do this on any car with the car running you will feel air blowing out of the oil cap. it will also make a pretty loud puffing sound.

DeLucia

My brothers civic does it, my built and turbo gsr does it, my old integra did it, buddies LS integra did it, friends k series did it. Its perfectly normal

djh781997

Turns out after further review of the EGR valve, it was stuck open. No I did not have a check engine light or any other symptoms of a bad EGR valve. Replaced the EGR valve and NOW it sounds "normal" when I take the oil cap off while the engine is running.

LPED

Hope you checked all the EGR passage ways cause a open EGR valve should make vehicle idle real bad, rough . A lot of times the passages get caked up .

DeLucia

The egr has nothing to do with pressure in the valvecover

someone else

I really doubt this. I've had several Hondas with EGR valves stuck open come through the shop and they all barely ran and wouldn't hold an idle.

Pressure from an open oil cap is normal. Leave your oil cap off and go for a drive then share your results.

Don't actually do that. It makes a huge mess.

__oversea

I have seen lots of older camry's with stuck EGR open. It barely idle and dies.

Anyways, It's perfectly normal pressure coming out of oil cap. lol