Leaking Valve cover = power loss??

**momento1** · 10-25-2009 01:19 AM

hi everyone...
im still having issues with my boost and power on my car. above all my boost guage needle shakes uncontrollablyand my boost creeps up past 25psi while it shaking (when i say shaking its more like bouncing back an forth really quickly)
previously my car had a slightly leaky valvecover gakset and a slight gushing sound under full boost (sounded like a boost leak but would come and go). Power was feeling pitiful at around 300whp. Couldnt find any physical boost leaks while doing a leak check.

Recently had my valve cover gaskets and cam seals re done. the car felt a heap better for a short while (even though my brand new N75 was causing it to boost up to 30psi so i was having to back off the throttle slightly)
after a short while the car has been making a gushing sound again but louder and with even less power. very similar to the one i had prior to the gasket change. noticed some oil leaking out of the rear of the valve cover again, (obviously wasnted sealed properly) so i can only assume its that.

However i have not heard that leaking valve covers would cause boost leak or considerable hp loss. Any ideas guys? this has been going on for over a year and it is ridiculously fustrating.

P.S also needing to install a oil catch can asap as i noticed that it is very greasy in the Y-pipe and samco hoses. And that cant help power one bit either.

**04/01-s4** · 10-25-2009 01:46 AM

Mine have been leaking since I bought the car....horribly.....but Im waiting to pull the motor to go stage III to do those. Honestly I cant imagine a leaking valve cover gasket to be a problem unless your turbos are collecting oil through the intake pipe somehow....Then I dont even know what it would do in that case. Your car really ran better after just replacing valve cover gaskets? The only sense that makes is that maybe a vacuum line was reconnected better and slowly worked its way out. I cant see your vacuum/pressure demands of a tuned engine resting on a proper seal between the valve cover?.. Id double check every vacuum line or possibly a line was somehow placed wrong and you'd just assume it was right? I havent torn my engine apart that far yet but..I wouldn't assume valve cover gaskets

**fas4tt** · 10-25-2009 08:07 AM

you should be careful if your leaking pretty bad, your car can catch on fire.... so you might want to check that out..

**RedRocketS4** · 10-26-2009 07:38 AM

i blew a turbo due to a leaking valve cover gasket... sucked. do a pressure test and find out for sure.something else might be bad.

**S4_NE** · 10-26-2009 11:54 AM

my buddy had a bad valve cover leak and the car ran like crap, me replace dit and the car ran better, we were shocked, i don'y ask how but it helped out with vacume, his car was just a stg 1 at the time

**mholme** · 10-26-2009 12:01 PM

It can indeed create a leak in the intake system.

**ScottM** · 10-26-2009 12:41 PM

both of mine leaked so bad the plugs were covered in oil causing misfires. check that too

**MattyJ** · 10-26-2009 01:14 PM

Your breather hose aka the "spider hose" could also be clogged causing an overpressure in your crankcase and your seals to blow out and your car to run like crap. If your intake is filled with oil this is a good place to start.

**momento1** · 10-26-2009 01:18 PM

Originally Posted by MattyJ

Your breather hose aka the "spider hose" could also be clogged causing an overpressure in your crankcase and your seals to blow out and your car to run like crap. If your intake is filled with oil this is a good place to start.

yeah i just recently replaced the entire spiderhose assembly.

hmm i might check that the plugs havent got any oil on them