| [GMCnet] MANIFOLD GASKET LEAKS [message #112702] |
Sat, 22 January 2011 21:54  |
Charles Aulgur
Messages: 78
Registered: March 2006
Karma: 0
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Member |
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From: Robert Peesel <thorndike@pldsllc.com>
Subject: [GMCnet] Maintenance question
Hello folks,
I am looking at a coach ('78 Royale) that has a spotless interior. I
have been reviewing the maintenance records and have noticed that
every 4 years or so, the manifolds were resurfaced and had a new
gasket installed. Eventually, the records show that the manifolds
were too thin to resurface and just had a gasket installed.
I can't figure out what would cause the manifold gaskets to be
replaced so often. Any thoughts?
Bob
Bob, take a look at the joint where the exhaust manifold connects to
the exhaust pipes on each side. A lot of muffler shops do not
replace the special spring-loaded bolts that came from the factory
for this flange connection. This connection should have a round
gasket with a spherical surface where it mates to the exhaust pipe.
The special bolts used there should have a shoulder that limits the
compression of the springs to a certain amount so the connection can
flex when the exhaust system expands and/or the engine moves around
on it's mounts. If this joint is not allowed to flex the engine
movement and exhaust pipe expansion puts to much load on the
manifolds and causes the manifold-to-head gasket to leak and erode
the manifold surface. You can see what the original configuration
looks like in the maintenance manual/parts book.
Chuck Aulgur
La Mesa, CA
76 Royale with great brakes
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| Re: [GMCnet] MANIFOLD GASKET LEAKS [message #112707 is a reply to message #112702] |
Sat, 22 January 2011 22:11  |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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| Charles Aulgur wrote on Sat, 22 January 2011 21:54 |
Bob, take a look at the joint where the exhaust manifold connects to
the exhaust pipes on each side. A lot of muffler shops do not
replace the special spring-loaded bolts that came from the factory
for this flange connection. This connection should have a round
gasket with a spherical surface where it mates to the exhaust pipe.
The special bolts used there should have a shoulder that limits the
compression of the springs to a certain amount so the connection can
flex when the exhaust system expands and/or the engine moves around
on it's mounts. If this joint is not allowed to flex the engine
movement and exhaust pipe expansion puts to much load on the
manifolds and causes the manifold-to-head gasket to leak and erode
the manifold surface. You can see what the original configuration
looks like in the maintenance manual/parts book.
Chuck Aulgur
La Mesa, CA
76 Royale with great brakes
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Chuck, I have always wondered about the connection. I have headers and I do not have that spring loaded connection. Do you think that this connection is required with headers installed?
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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