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Question:"Blow-by" in valve cover

07-22-2004, 12:02 PM
So during the quest to diagnose my most recent engine issues, I was told by one mechanic that I had a lot, an unusual amount, of "blow by" in the valve cover. He said that it was likely cause by the cold air intake and a poor vacuum hose from the valve to the intake.
He took the oil cap off and put his hand over it and amusingly watched the cap bounce around.

My question is, is this a monster issue? As I am, as I type, having the motor replaced (cheaper than having internal work done) I don't want any problems from the first motor to carry over into the new one, is this blow by a monster issue? Should I toss the vacuum hose that came with the intake and use a narrower hose to increase the vacuum velocity? Long term effects?

thanks again AF

08-23-2004, 01:08 PM
I am curious about this same issue. I have oil getting pushed into my air intake out of the valve cover.

08-23-2004, 04:09 PM
that is blowby, usually caused by broken ringlands causes pressure to get by rings and into crank which is pushed out into the head out through that hose to the intake

08-23-2004, 04:48 PM
sounds more like a bad pcv valve to me
go to auto parts store and buy one there like 5$.
try this on ur own too

08-23-2004, 05:20 PM
doubt its a bad pcv valve because there shouldnt really be any blowby at all. so if its stuck open then there still shouldnt realy be any blowby, if it was close then there shouldnt be any blowby.

pcv valve doesnt create blowby. doubt its the pcv valve.

i doubt its a bad vacuum hose because that oil cap trick wouldnt happen if it was a leak at the valve to intake

08-23-2004, 05:39 PM
not arguing wiht u just say my opinion but if the pcv valve doesnt open then gases created in the oil pan have to escape from somewhere and if the pcv valve is closed the the gasses retrun back to the intake hose. right?

08-23-2004, 06:23 PM
let me guess, it was an old school mechanic. Take any DOHC honda and loosen the cap, i bet it will rattle around just like yours. The engine has two cams right next to that oil fill hole in the valve cover, and those cams are spinning pretty fast. This is gonna cause pressure in the valve cover. Mine does the same thing and i have perfect compression and hardly any leakdown at all, both of which would cause blow by if messed up.

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