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1994 Chevy Cheyenne Exhaust leak

Tiny
BOOMERJOE99
  • MEMBER
  • 1994 CHEVROLET CHEYENNE
  • V8
  • 4WD
  • AUTOMATIC
  • 165,000 MILES
Just replaced driver side exhaust manifold, did not use any type of gasket. Manifold is leaking at higher RPM's at middle and last connection fitting. Any suggestions on how to fix problem, should I have used some type of gasket, scared to crank down on bolts, don't want to break them.
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Sunday, January 25th, 2009 AT 1:58 PM

7 Replies

Tiny
2CARPRO JACK
  • MECHANIC
  • 11,533 POSTS
What size engine is it?The big blocks (7.4L) need to be cut inbetween the ports and then surfaced. The small block ones will warp too and need to be surfaced on occasion. If the bolts are tight and it leaks, you may need to surface it. At most I have used avery thin layer of sensor safe hi-temp silicone, but not a gasket
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Sunday, January 25th, 2009 AT 3:01 PM
Tiny
BOOMERJOE99
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  • 8 POSTS
The engine size is the 5.7 L. The exhaust manifold I put on is brand new. When you say surface to you mean cleaning up the surface of the exhaust manifold and cleaning of the engine block.
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Sunday, January 25th, 2009 AT 6:03 PM
Tiny
2CARPRO JACK
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No, surfacing is when they machine the mating surface flat. Try the thin layer of silicone (sensor safe) You can crank them down pretty tight without breaking them. Does only the one side leak?
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Sunday, January 25th, 2009 AT 7:25 PM
Tiny
BOOMERJOE99
  • MEMBER
  • 8 POSTS
Yeah only the one side leaks, and its only the middle and the one that is closest to to the firewall that is leaking. I don't drive the truck much but it seems that it is leaking less now than it was when I first installed the manifold. The only reason I know there still leaking is I have sprayed soaping water on the manifold when the engine is cold and started the engine up. I can't actually hear it leaking anymore. Should I just wait and see if the manifold conforms to the block a little bit more before I try the silicone?
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Tuesday, February 3rd, 2009 AT 4:07 PM
Tiny
2CARPRO JACK
  • MECHANIC
  • 11,533 POSTS
Yes, sometimes they fill in the gaps with carbon from the exhaust and like you said, they heat up and conform a little
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Tuesday, February 3rd, 2009 AT 4:10 PM
Tiny
BOOMERJOE99
  • MEMBER
  • 8 POSTS
Thanks, I appreciate your help.
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Tuesday, February 3rd, 2009 AT 4:19 PM
Tiny
2CARPRO JACK
  • MECHANIC
  • 11,533 POSTS
Any time
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Tuesday, February 3rd, 2009 AT 4:27 PM

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