| Exhaust Leak [message #278724] |
Sat, 30 May 2015 13:20  |
bhayes
Messages: 263
Registered: March 2010
Karma: 1
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We've had problems with an exhaust smell making its way into the coach. I've been working underneath the engine and noticed soot marks coming down from the exhaust ports onto the block. I'm assuming these are from a leaking exhaust gasket (I'm using Thorley headers, by the way). Here's a picture:
http://www.gmcmhphotos.com/photos/mechanical/p58026-exhaust-gasket-leak.html
Anyone think otherwise?
Bryan Hayes
'76 Eleganza II
Salt Lake City, Utah
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| Re: Exhaust Leak [message #278739 is a reply to message #278724] |
Sat, 30 May 2015 18:00  |
tphipps
Messages: 3005
Registered: August 2004
Location: Spanish Fort, AL
Karma: 9
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Senior Member |
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I would expect the exhaust gasket failed. Replace it with the Remflex gasket (from JmK and others), follow the install instructions (torque limited to 20) and be happy. Do not tighten the top middle bolt to high tension. It just holds everything in place while you set the 4 bolts that do the actual work. the top bolt, if tightened will tilt the manifold toward the top of the exhaust ports, and allow leakage from the bottom edge. I had a similar leak, first replaced it with NAPA exhaust gasket, it failed quickly, then installed Remflex gasket. No leaks yet and it has been 3 long and hard trips since the replacement. Remflex is pure graphite, so handle it with care. Do not bend or twist it, it can be broken until installed.
http://www.appliedgmc.com/prod.itml/icOid/670 (Remflex Gasket Set)
JmK also has the Thorley exhaust gasket, but I have no experience with either the headers or the gaskets.
http://www.appliedgmc.com/prod.itml/icOid/673 (Thorley Gasket Set)
Your mileage may vary, but this is where I would start.
Tom, MS II
2012 Phoenix Cruiser model 2552
KA4CSG
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| Re: Exhaust Leak [message #278741 is a reply to message #278739] |
Sat, 30 May 2015 19:09 |
bhayes
Messages: 263
Registered: March 2010
Karma: 1
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Senior Member |
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Thanks, Tom. The Thorley and Remflex gaskets look pretty much identical shapewise. Is it recommended to use the Thorley gasket with the Thorley headers?
Bryan Hayes
'76 Eleganza II
Salt Lake City, Utah
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| Re: [GMCnet] Exhaust Leak [message #278743 is a reply to message #278739] |
Sat, 30 May 2015 19:01 |
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USAussie
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
Karma: 6
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Senior Member |
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Tom,
Good on yah, Mate! I have NEVER read the following on the GMCnet before:
"Do not tighten the top middle bolt to high tension. It just holds everything in place while you set the 4 bolts that do the actual
work the top bolt, if tightened will tilt the manifold toward the top of the exhaust ports, and allow leakage from the bottom edge."
I agree 100%!
Regards,
Rob M.
The Pedantic Mechanic
Sydney, Australia
-----Original Message-----
From: Thomas Phipps
I would expect the exhaust gasket failed. Replace it with the Remflex gasket (from JmK and others), follow the install instructions
(torque limited to 20) and be happy. Do not tighten the top middle bolt to high tension. It just holds everything in place while
you set the 4 bolts that do the actual work. the top bolt, if tightened will tilt the manifold toward the top of the exhaust ports,
and allow leakage from the bottom edge. I had a similar leak, first replaced it with NAPA exhaust gasket, it failed quickly, then
installed Remflex gasket. No leaks yet and it has been 3 long and hard trips since the replacement. Remflex is pure graphite, so
handle it with care. Do not bend or twist it, it can be broken until installed.
http://www.appliedgmc.com/prod.itml/icOid/670 (Remflex Gasket Set)
JmK also has the Thorley exhaust gasket, but I have no experience with either the headers or the gaskets.
http://www.appliedgmc.com/prod.itml/icOid/673 (Thorley Gasket Set)
Your mileage may vary, but this is where I would start.
Tom
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Regards,
Rob M. (USAussie)
The Pedantic Mechanic
Sydney, Australia
'75 Avion - AUS - The Blue Streak TZE365V100428
'75 Avion - USA - Double Trouble TZE365V100426
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| Re: Exhaust Leak [message #278755 is a reply to message #278739] |
Sat, 30 May 2015 23:13 |
bhayes
Messages: 263
Registered: March 2010
Karma: 1
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Senior Member |
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"Do not tighten the top middle bolt to high tension. It just holds everything in place while you set the 4 bolts that do the actual
work the top bolt, if tightened will tilt the manifold toward the top of the exhaust ports, and allow leakage from the bottom edge."
Interesting. I have to wonder if this is what whoever installed my coach's Thorleys did (they were already installed when I purchased it). I have soot marks on both sides of the engine coming from the bottom edges of the headers. I suppose tightening that top middle bolt could cause premature gasket failure.
Bryan Hayes
'76 Eleganza II
Salt Lake City, Utah
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| Re: Exhaust Leak [message #279411 is a reply to message #278739] |
Tue, 09 June 2015 00:57 |
bhayes
Messages: 263
Registered: March 2010
Karma: 1
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Senior Member |
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I replaced the header gaskets this weekend with the Remflex gaskets (thanks for the fast shipping, JimK and Nick!). Looks like that took care of the exhaust leak. I could clearly see on the old gaskets--which appeared to be copper--where the exhaust was leaking by. My wife is much happier without the exhaust smell.
Thanks for the help, everyone. Now on to getting the steering gear adjusted.
Bryan Hayes
'76 Eleganza II
Salt Lake City, Utah
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