Boost leaking from valve Cover

[Huz]

Ever since changing a pcv hose that forced boost into the crankcase I have noticed my car to be a lot slower and only making 5psi when it is set to 10. Could this pcv valve be stuck open causing a boost leak because this would explain why the hose was like that.

http://www.toymods.org.au/forums/showthread.php?t=59067

[william]

block both the pipes in the picture and replace the other one

it would seem to me that you are loosing boost through the T'd pipe which I'm assuming is for idle air control, does the T'd hose go before the turbo? if so then thats why you lost 5psi boost!

if not then i don't know!

[Huz]

First I tried blocking off the pipe that goes into the throttle body and it did nothing. Then I re-connected it and blocked off the hose that goes into the t piece (the way it was when I got it) and it was boosting properly again.
So whats happening is the boost is leaking into the head somewhere. I will do a compression test on the car but I doubt it has much blow-by as it doesn’t use any oil or blow smoke.
Is there any other breathers on a 7mgte or is it just the 2 on the valve covers. Im thinking that a hose or something might be wrong.

[william]

the pipe going to the T piece is where the boost is going. if you blocked the one going to the throttle without blocking the T'd pipe it wouldnt make a difference. I'm not familiar with 7m's so i dont know where the pipe going to the throttle comes from.where do the pcv valves on the valve covers connect up? may be worth your while fitting a catch can and just blocking the pipes as mentioned?

[Huz]

Its been a few weeks now and I have tried blocking off each of the hoses and the boost is leaking from inside the valve covers. it also seems to be creating vacuum sucking into the valve cover.

Im going to get the car compression tested but I dont think its the problem because it hasnt used any oil at all and doesnt blow any smoke.

Any ideas on what is causing this

["Z" UTE]

Huz, the PCV valve should open and allow flow from the rocker cover to the intake, effectively putting the crankcase mist and air into the cylinders to be burnt. If you are getting boost into the rocker covers, the PCV valve is FUBAR, or installed backwards.

cheers Chuck.

[stan]

Agree ^ or rings but that would blow smoke or valve related. There should be no boost in the crank case unless it is being fed in by a hose of some description. (I would recomend not doing that by the way) compression test and see what happens!!!!!

[oldcorollas]

err.. doesn't the cam cover vent to before the turbo? so that there is never any positive pressure in the engine (unless there is too much blowby) and when PCV valve is sucking, then the breather allows air into engine?

seems you need to take a fundamental look at the pipes in question, and work out where you went wrong

[Duk]

err.. doesn't the cam cover vent to before the turbo? so that there is never any positive pressure in the engine (unless there is too much blowby) and when PCV valve is sucking, then the breather allows air into engine?

seems you need to take a fundamental look at the pipes in question, and work out where you went wrong

I'm don't know anything about the 7mgte crankcase ventilation system, but my RB20 uses a 1 way valve so that the engine can suck crankcase gases straight into the inlet manifold when there is no boost pressure. Under boost the gases vent to the turbo inlet, after the air flow meter.
Does the 7mgte use a 1 way valve in its system? Is it stuck or in back to front?

[oldcorollas]

the one way valve is the PCV valve..
positive crankcase ventilation...

but it is not positive pressure... the vacuum of the intake, and the incoming air through the breahter into the crankcase "positively" vents the air from inside the engine.. ie, actively

they should call it "active crankcase ventilation" instead, to stop confusing people