LT1 Based Engine Tech 1993-1997 LT1/LT4 Engine Related

Intake manifold gasket, anybody have this?

Old 09-30-2015, 02:41 PM
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Intake manifold gasket, anybody have this?

I finally decided to fix the oil leak in my 94 z28, you know, the infamous sealant leak in the back. Purchased a felpro gasket set and installed everything as per the factory service manual. Took my time, did it right, changed out many old vacuum hoses (some where getting cracked), started the car and it ran like total crap (actually barely ran at all, ran great before I started), seemed like a massive vacuum leak. Analyzed it to leaky fuel injector O-rings, replaced them with a/c delco ones (they actually were slightly bigger than the felpro ones), car runs a little better but still barely able to run. Vacuum leak still exists, (as evidenced by no power brakes almost at all).

Anybody else go through this, I'm, looking for ideas before I tackle this again.
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Old 09-30-2015, 05:24 PM
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Re: Intake manifold gasket, anybody have this?

Triple check your work.
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Old 10-05-2015, 06:30 AM
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Re: Intake manifold gasket, anybody have this?

If you can't hear it, try a smoke and see if you can see it go into the engine at the leak. There are several you tube videos on how to install the intake manifold. When installing the manifold, it's easy to disturb the RTV on the rear wall of the block.
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Old 10-05-2015, 11:23 AM
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Re: Intake manifold gasket, anybody have this?

I would agree with the "triple check" advice. I recently just did the work you are describing. Took a long time to find all the pics showing proper vacuum routes, they can be a bit confusing. Could you expand on what you were talking about when you said "the infamous sealant leak in the back". I actually just developed a leak in the back after i did the work.
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Old 10-05-2015, 01:57 PM
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Re: Intake manifold gasket, anybody have this?

Originally Posted by FredM View Post
I would agree with the "triple check" advice. I recently just did the work you are describing. Took a long time to find all the pics showing proper vacuum routes, they can be a bit confusing. Could you expand on what you were talking about when you said "the infamous sealant leak in the back". I actually just developed a leak in the back after i did the work.
The main reason the rear of the manifold to block is the application of RTV and disturbing the bead as the manifold is lowered to the block. If you had to move the manifold after trying to set it on the heads and block to line up the holes for bolts, many times the RTV bead is disturbed and a leak can follow. The old fashion way was to use that rubber gasket which always slipped out of position. Never use that gasket which sometimes is in the intake manifold set.
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Old 10-05-2015, 02:44 PM
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Re: Intake manifold gasket, anybody have this?

Originally Posted by FredM View Post
... Could you expand on what you were talking about when you said "the infamous sealant leak in the back". I actually just developed a leak in the back after i did the work.
The "infamous" leak came to be when the cars were new. The factory seal at the back of the intake to the block was marginal and many people developed a leak. GM issued a TSB to have the leak fixed under warranty. Clean surfaces, a proper amount of good sealant and careful attention to dropping the intake on should make that a non-factor for the DIY crowd.

BTW, A leak there will not cause a vacuum leak. It will let crankcase vapors and/or oil out.
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Old 10-06-2015, 11:18 AM
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Re: Intake manifold gasket, anybody have this?

Thanks for helping shoebox, thats good information to know.
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Old 04-15-2016, 03:08 AM
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Re: Intake manifold gasket, anybody have this?

Originally Posted by magman View Post
I finally decided to fix the oil leak in my 94 z28, you know, the infamous sealant leak in the back. Purchased a felpro gasket set and installed everything as per the factory service manual. Took my time, did it right, changed out many old vacuum hoses (some where getting cracked), started the car and it ran like total crap (actually barely ran at all, ran great before I started), seemed like a massive vacuum leak. Analyzed it to leaky fuel injector O-rings, replaced them with a/c delco ones (they actually were slightly bigger than the felpro ones), car runs a little better but still barely able to run. Vacuum leak still exists, (as evidenced by no power brakes almost at all).

Anybody else go through this, I'm, looking for ideas before I tackle this again.
I know this is an old tread but it could help some one i had the same problem for a vacuum leak to find the leak i started the angine while the engine running i sprayed some map sensor cleaner around the intake manifold when you get close to the leak the car starts idleing rough and sometimes the engine will shut off is like adding too much gas to a carburator so i found the leak it was the hose that goes from the brake booster to the engine it has a little piece of pipe that bents really easy i took it off and used some high temp silicone installed it back and its been running like a champ for almost a year
Sorry my english is not really good camaro 3.8 1997
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