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2G Boost leaking from intake manifold

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murr1979

Probationary Member
12
0
Oct 12, 2009
colorado spring, Colorado
I performed a boost leak test and thought my BOV was leaking but it turned out to be the tubing coming from the intake manifold going into the BOV nipple is this normal to have air coming out of this tube? I'm only running 5-10 psi. Was wondering what would cause this.
 

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What do you mean tubing? Do you mean the vacuum line for the bov? If so replace it probably has a crack/split in it.
Yes the vacuum line but it's not the tubing. The air is coming out of the nipple on the intake manifold through that tube. I think it's supposed to be a vacuum and not air pressure but not sure why it has pressure with the throttle closed.
 
Yes the vacuum line but it's not the tubing. The air is coming out of the nipple on the intake manifold through that tube. I think it's supposed to be a vacuum and not air pressure but not sure why it has pressure with the throttle closed.

If you're asking if the line to the bov is supposed to get pressure from the manifold, yes it is. It should not be leaking out of the nipple or the line though. Not 100% sure which you mean.
 
Ok I hooked up a boost leak tester and set it to 5 psi. I have air coming through out of the vacuum line from the nipple on the intake manifold. I thought I should not have any air coming out anywhere. Is this a leak or normal while doing a boost leak test? The throttle body is closed.
 
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Thank you, that's what I thought. So based on your knowledge and experience experience should I start with the throttle body?
 
You're confusing me bud, if the vacuum line is leaking, as in it's torn, cracked, gouged, I'd start by replacing that.

If you are asking if pressure should be going through that line from the intake with the throttle closed. Yes that's normal, air will leak past the throttle plate into the manifold during a BLT. There are a few paths around the plate, the BISS, the fiav, and the ISC.
 
Yeah I just realized my wording might be confusing. My car is all stock and want to keep it that way. I'll start from the beginning. I notice a large loss in power, it's as if I don't have a turbo in the car anymore. The turbo spools up. I can hear it and the gauge shows it's boosting but I can hear a loud air leak while driving. When I change gears I don't hear the BOV. I hooked up a boost leak tester and found air coming from my 2G original BOV so I replaced it with a used 1G BOV. I then did another boost leak test and it's doing the same exact thing. I thought when you do a boost leak test there should be no air coming out of anything especially at 5psi. My vacuum tube/hose is fine and the nipple on the intake manifold is fine. Nothing is cut or dry rotted. With my boost leak tester hooked up and at 5 psi should I expect air coming out anywhere? The air I am getting is coming out the manifold and feeding to the BOV through that vacuum line causing the BOV to open thus losing the air. It is NOT leaking through anything. If I remove the tube and plug it with my finger then the BOV leaks after air builds up. My question is should I expect air coming from that tube through the intake manifold while under pressure? Is it supposed to have air pressure there and the BOV is not holding the air? I'm thinking I may had replace a bad BOV with another bad BOV? I'm sorry for the essay but I'm at the point of going to the dealership for repairs or trade in at this point.
 
Okay, I think I understand you now. That line going to the top of the bov gets pressure during boost and that helps hold it shut. Then when the throttle shuts it quickly sees vacuum there and opens.

If your BOV won't stay shut under pressure it's probably no good. Try doing your BLT with the throttle wedged open.
 
I know it's late now but finally got the boost leak fixed. The exhaust gasket on the turbo was bad. Replaced it and now have boost pressure holding like should. It did not make sense to me why that would cause loss of power but i'm happy it's fixed. Thanks for the help received.
 
Glad you were able to get your problem resolved. Next time you get a boost leak or think you have a boost leak you can use carb cleaner or starter fluid and spray it around. If you hear the engine choking or reviving up you know you have a problem in that area.
 
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