Leaking upper intake AGAIN - Page 4 - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


1992-1999 Series I L27 (1992-1994 SE,SLE, SSE) & Series II L36 (1995-1999 SE, SSE, SLE) and common problems for the Series I and II L67 (all supercharged models 92-99) Including Olds 88's, Olds LSS's and Buick Lesabres Please use General Chat for non-mechanical issues, and Performance and Brainstorming for improvements.

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Old 02-28-2005, 11:26 PM   #31
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Quote:
Originally Posted by vital49
Hey Don... Can you circle on my pic where you're specifically talking of? I may very well have a flaw, but not know it. What should it look like?
Hey Vital, I'll have to post a pic or two tomorrow sometime... I think it may just be a casting mark, like a jagged edge... I have something simmilar on mine as well...

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Old 03-01-2005, 12:46 AM   #32
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Quote:
Originally Posted by ron350
There are two machined holes in the lower aluminum intake manifold for the coolant that goes up through the plastic intake to the Throttle Body. These holes are on ether side of the EGR pipe sticking up on the throttle body end of the manifold. If you take the plastic manifold off and tap and plug these two holes there will no longer be any coolant to leak. Once these holes are plugged the only leak you can have with the plastic intake is a vacuum leak.
If your car is idling fine now you can do this and reuse the upper gasket and upper manifold.
Keep in mind that if you do this, you loose anti-icing capability. That is the reason that the T/B was heated in the first place.
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Old 03-01-2005, 05:06 AM   #33
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As Gilda Radner used to say “never mind”
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Old 03-01-2005, 10:13 AM   #34
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I see what you're talking of Don. Ya, that'* just a casting mark. When I had the lower off in May to do the gaskets it was in excellent condition. Hasn't overheated or anything since...

I agree, blocking off ports in the upper only defers heat to the remaining open ports/channels. That, in a sense, is just making it hotter in other locations. It will just make the plastic weaker in that area where all the coolant is being defered to.
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Old 03-01-2005, 10:18 AM   #35
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I'm thinking those coolant passages in the plastic plenum do more than just provide heat to prevent icing. I believe they also cool the plastic that is exposed to heat from the EGR pipe. I just re-did my plenum and replaced the stock EGR stovepipe with a reduced diameter EGR pipe to provide some air space between the hot pipe and the plastic upper. 57ChevyThunder recommended this in an earlier thread. KenCo makes a kit to repair EGR heat damage and to prevent future deterioration for $80 delivered to your door.

Anyway, I would be concerned that blocking the coolant flow without also disabling the EGR would lead to an even more rapid deterioration and warpage of the plastic. This seems like a good formula for vacuum leaks. My upper was warped at the TB joint and disintegrating around the EGR pipe. And I think I have read here that blocking the EGR flow is not the best plan for several reasons. Now, vacuum leaks are way better than coolant leaks, but better yet is no leaks.

An aluminum plenum with an appropriate TB adapter plate is what we really need. Until then, the best fix I have seen is a new upper, new upper and lower gaskets and a reduced diameter stove pipe.
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Old 03-01-2005, 01:58 PM   #36
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Vital,
Come to think of it my car did that in the same spot about a month after I assembled the intakes.
The plastics seem to have compressed under heat.
It was the long bolt with the nut on top that was loose. I retorqued it and its been dry since.
Pop that fuel rail off and re-torque that puppy to 11 and you should be all set.
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Old 03-01-2005, 03:08 PM   #37
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Default Re: leak

Quote:
Originally Posted by SSEBONNE4EVA
Vital,
Come to think of it my car did that in the same spot about a month after I assembled the intakes.
The plastics seem to have compressed under heat.
It was the long bolt with the nut on top that was loose. I retorqued it and its been dry since.
Pop that fuel rail off and re-torque that puppy to 11 and you should be all set.
That'* got me thinking now...

One night this week I'll take the fuel rail off and retorque everything before I get into a full new upper. I should put some thread locker on it to prevent them from loosening....or will that do any damage to the lower?
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Old 03-01-2005, 03:42 PM   #38
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No, threadlocker is what was specified for mine ('95) in the FSM. I used medium (blue). Hope they hold!
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Old 03-01-2005, 04:32 PM   #39
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Quote:
Originally Posted by bill buttermore
No, threadlocker is what was specified for mine ('95) in the FSM. I used medium (blue). Hope they hold!
Thanks for the tip, Bill. Did not know it was protocol. Hopefully we're on to something here.....
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Old 03-01-2005, 05:19 PM   #40
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Hey Vital, I just checked the books. Threadlock is NOT specified for the upper - only for the lower intake manifold. I did use it on both of mine however. I haven't tried to disassemble it, so I can't say that it won't cause problems if I have to change out the plastic plenum. (Not an unlikely possibility in these cars.) I guess it might mess up the threads in the softer aluminum of the intake. The lower intake bolts are into the cast iron of the heads. No problem there. But I can't advise that you do what I did, and use it on the upper.
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