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Discussion Starter #1
Ever since I got my car running I have had a bad vacuum leak at the intake manifold gasket. It is right at the #4 intake port next to the vtec solenoid. I've tried two gaskets, a hondata thermal type gasket, and an oem z6 gasket. Both leak in the same spots, verified by spraying carb cleaner around the area and also pressurizing the system with a compressor (with engine off). I took the intake mani to my machinist today to get the face milled true but he put a straight edge on it and it's perfectly fine.

So, what next? They suggested I try some silicone gasket around the leaking area, which might work, but I still don't know what the real problem is. Any other suggestions?

Justin

edit: setup is a z6 head, and a y8 intake manifold.
 

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Discussion Starter #3
Make sure both surfaces are clean and no indents or major scratches on there...
Yea, been over that already. The head was rebuilt and resurfaced by machine shop, it should be fine. When we observed the leaks it looks like it is coming from between the gasket and IM. The OEM gasket leaked more then the thermal thick plastic one did too. I don't get it ... :(

Justin
 

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I guess you could try some silicone or RTV, but be careful out to allow any to seap into the motor!
 

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Discussion Starter #5
I guess you could try some silicone or RTV, but be careful out to allow any to seap into the motor!
Yea, I put it back together with the thermal plastic gasket and a thin layer of silicone in on each side of the gasket where it was leaking. See how it works after it sits for a few hours.

Justin
 

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Found your problem digging through your thread pictures.

Your head is a 96-98 head, and your intake manifold is a 99-00 piece. The 99-00 piece has air injection holes above the runners which must be plugged, or you get a vacuum leak. People use JB weld and such to fill them.

Apologies for the huge pic link to your site, but it is the only way to clearly see the holes. ;)
 

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Discussion Starter #7
Found your problem digging through your thread pictures.

Your head is a 96-98 head, and your intake manifold is a 99-00 piece. The 99-00 piece has air injection holes above the runners which must be plugged, or you get a vacuum leak. People use JB weld and such to fill them.

Apologies for the huge pic link to your site, but it is the only way to clearly see the holes. ;)
You know we were wondering about those little holes, cause the gasket only covers about half of them. But we couldn't seem to confirm the vacuum leak on all 4 holes.

Guess I'll take it all apart again and fill them up. Luckily I got some JB weld I just bought :D

Justin
 

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Discussion Starter #8
Found your problem digging through your thread pictures.

Your head is a 96-98 head, and your intake manifold is a 99-00 piece. The 99-00 piece has air injection holes above the runners which must be plugged, or you get a vacuum leak. People use JB weld and such to fill them.

Apologies for the huge pic link to your site, but it is the only way to clearly see the holes. ;)
Great success!!

JB welded those things up and put it back together. Car purrs like a kitten now, no more vacuum leaks and bouncing idle!

Thanks again for the tip!

PS: After looking at the IM closer, it looks like the injector o-rings are supposed to seal those holes. That probably explains why we were only seeing 1 leak bad. Plugging them up serves same purpose.

Justin
 
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