boost leak :(

i noticed the other day that my gauge will spike to 16 then instantly fall to 10 and hardly hold 10. leak tested it today...few questions.

the circular seal for the valve cover (the half circle gasket)...when i blow 10 psi or greater, i can see stuff bubble from it. is this a problem?

there is definitely a leak near the intake mani. if i blow anymore than 10psi all i can hear is a huge leak. it sounds like it's coming from behind the manifold, but i can't pinpoint it.

i used soapy water for the throttle body. some got down in the BISS hole. when i blew air into the system, it literally squirted/bubbled instantly from the BISS. so then i plugged my finger over it to see if that was the leak i was hearing. nope. the leak definitely sounds like it's behind the intake mani...

any help would be great. thanks.

You check the 2 sides of the TB for the shaft seals?

The int. manifold gasket could be goin.....

From what i've heard the int. manifold is kinda a bitch to do with the engine in the car....unless you got go go gadget arms...he he he
I think I remember someone telling me there is a bolt for a mount that goes right into the bottom/back side of the int. mani and that has been known to leak... just a few thoughts....

the intake manifold gasket has no more than 4,000 miles on it....i replaced it when i had the motor out. i remembered something though....a long time ago when i got a new tb gasket, i got it home and it was for a first gen but i made it fit because the place i got it from always somehow sells me wrong parts.....i just looked at it again and when i put soapy water on the tb and blow air, the leak sounds different...it sounds like it's blowing the water but i looked and it's not bubbling or anything....

I could be wrong, but I seem to remember that on either 1g or 2g, but probably not both, one of the support bracket bolts goes through. Not plugging that can leave a large leak. But again, I can't remember it or picture it from my own experience, so I can't offer this with 100% confidence. It will give you something besides the gasket to look at though.

Edit> I'm also making the assumption that you removed that bracket and left it off, the last time you worked on the manifold ;)

nope, the bracket is on and all bolts are in the holes. i did however fix my leak. got a new tb gasket and put it on and i also noticed, before i replaced the gasket, that it wasn't spiking at 16 anymore, it was just topping off at 11. so i replaced the gasket and examined my MBC....someone tampered with it because the nut was loose. so i upped the boost a tad and tightened the nut. took it for a test drive, spiked at 17 leveled right at 15-16! :) you don't understand how much harder it pulls now lol. i wasn't used to that much boost cause it's been at low boost for the past few days.

You might wanna check into the cam plug (the half moon seal) a little more. You shouldn't really have that much pressure in the head and it might be worn or damaged valve seals. It could also just be that seal is worn or damaged.

While we're on topic, I thought I'd just add instead of posting another thread...

Does the boost gauge have to rise then fall to a steady reading to indicate boost leak? I havent had the time to make a decent tester, but at 10 psi (at least thats what the gauge reads!) the spooling noises are very loud and the car seems to pull equally hard at 15 psi as it does at 10 psi... I will eventually have to get a tester done soon, but any opinions/comments?

Nothing the boost guage shows you can indicate a leak. You have to have a tester.

Nothing the boost guage shows you can indicate a leak.


Thanks for clearing up a misconception I had Kevin. I'm going to make a tester before school starts, hopefully. I'm almost positive I have lots-a-leakin'.