96 century 3.1 115k oil leak? - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 03-08-2014, 01:55 PM   #1
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Default 96 century 3.1 115k oil leak?

3 years ago I had the LIM gaskets changed by a reputable[?] shop and the car has ran just like new. Noticed lately there'* oil leaking in the intake valley. Is there some thing else that might leak oil in the intake valley besides the LIM gaskets? I'm thinking of retorqueing all the bolts to see if it will help at all. Supposedly the improved felpro gasket set was used and only lasted 5k miles/3 years, should last longer than that. It is a minor leak, just drops per parking incident. Any ideas or suggestions? Is the oil leaking under pressure or just running down the side walls? I'm thinking the only way to fix correctly is a total r&r?

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Old 03-08-2014, 03:03 PM   #2
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New gaskets relax and have to be re-torqued. I would tighten everything down again and see if that clears it up. When the weather cleans up you can clean the engine so you can see if it is still leaking.
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Old 03-08-2014, 05:28 PM   #3
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if they didnt use sealant on the bolts it can leak from there or if they didnt torque it to the right values or pattern. from the service manual for your car;

Install lower the intake manifold attaching bolts. Apply sealant GM part no. 12345739 or equivalent to the threads of bolts, and tighten bolts to 115 inch lbs. (13 Nm).
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Old 03-08-2014, 05:34 PM   #4
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Thanks, tomorrow I'll eyeball those bolts and see wassup.
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Old 03-08-2014, 06:09 PM   #5
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If the bolts indeed loosen, they should've applied red lock tite to the bolts. Another possibility is the silicone they used across the lower intake to the engine block is leaking. And almost forgot if the leak is on the back of the block, check the oil pump drive.
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Old 03-29-2014, 12:34 PM   #6
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Chevy82 on this motor [96 model] I've looked at pics on bing image search and it seems the oil pump drive is right below the throttle body, but on mine it'* nowhere to be seen. Is mine a second gen 3.1 and does it matter? Those LIM bolts are buried and the upper IM needs to come off to check the torque on them. Going to do that soon. Need info on location of that oil pump drive to check it.......TIA. This oil leak is getting worse and the oil is as clean as new so it'* hard to follow a trail, full syn too. I know there'* oil in that valley because I can see it, just not where it'* coming from.
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Old 03-29-2014, 02:59 PM   #7
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Well, if those bolts are loose, retorquing is only a temporary solution......I suppose you can take the upper plenum off, and do one bolt at a time, in the proper sequence....but if those bolts are loose, I would completely remove the bolt, apply the sealer to the threads, and then torque it......one bolt at a time, in the proper sequence......all those bolts are not torqued the same......the two external end bolts are torqued more......

Plus once you have the upper plenum off, you can check if that dummy distributor shaft is leaking......but, the o-ring and gasket are usually done with the intake job.....

Another thing you can try before this, is adding oil dye to the oil....run the vehicle for a day and then check with a black light......it may be the RTV that is not properly sealed in the four corners of the valley...

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Old 03-29-2014, 11:36 PM   #8
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Its right below the throttlebody, looks like a plug. And sometimes the O-ring doesn't get replaced, if the plug is really tough to remove. Seen it happen.
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