| Loud Exhaust [message #303012] |
Sun, 03 July 2016 19:04  |
Jim Schulte
Messages: 9
Registered: January 2016
Location: Strawberry Point, IA
Karma: 0
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Junior Member |
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Had unit at local mechanic, and asked him to correct excessive exhaust noise thinking the doughnut was out. His opinion is the heads are cracked. I had him do a compression test and he stated compression in all cylinders is from 140 to 145 and the doughnut is OK. He said he thought there is a head crack at the exhaust manifold that does not extend into the cylinder on both heads. 1977 23ft Birchaven with 133000 mi and a 455. I do not understand cracked heads? I would suspect a bad exhaust manifold gasket and if so any recommendations on bolt removal and replacement of gasket. Jim
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| Re: Loud Exhaust [message #303014 is a reply to message #303012] |
Sun, 03 July 2016 19:21  |
Carl S.
Messages: 4186
Registered: January 2009
Location: Tucson, AZ.
Karma: 13
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Senior Member |
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Sounds like you need a new mechanic, or at least a second opinion. More likely you have bad exhaust manifold gaskets or maybe a cracked exhaust manifold. There are several options on gaskets. Dave Lenzi makes a nice embossed copper gasket and includes explicit instructions on installation (what I have): http://bdub.net/lenzi/index.html
Others have had good luck with Remflex gaskets: http://appliedgmc.com/prod.itml/icOid/670
The bolts may need to be soaked with penetrating oil and be removed carefully. Sometimes it helps to give them a hit with a hammer, and/or tighten them a little before trying to remove them. Installation should be with the four lower bolts first, tightening them to spec, then installing the top bolt last with less torque. All five bolts are above center line of the manifold and tightening the top one can tilt the manifold, creating a leak at the bottom.
Carl Stouffer
'75 ex Palm Beach
Tucson, AZ.
Chuck Aulgur Reaction Arm Disc Brakes, Quadrabags, 3.70 LSD final drive, Lenzi knuckles/hubs, Dodge Truck 16" X 8" front wheels, Rear American Eagles, Solar battery charging. GMCSJ and GMCMI member
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| Re: Loud Exhaust [message #303017 is a reply to message #303014] |
Sun, 03 July 2016 19:55 |
tphipps
Messages: 3005
Registered: August 2004
Location: Spanish Fort, AL
Karma: 9
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Senior Member |
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I would suspect blown exhaust gasket or cracked exhaust manifold. One of the ears on the manifold may have broken. I've got one that I'm watching now.
Remflex gaskets are the way to go with a suspect manifold seating problem. Read the directions carefully. Do not over-torque the gasket . You can crush it and render it useless. Do not tighten the middle bolt on the manifold, it's purpose is to hold the manifold to the block while setting the other 4 bolts. Torque the four bolts in the pattern in the instructions. After finishing the job, re-torque the bolts after the engine has been driven for several heating and cooling cycles. Did I say, do not torque the center bolt, just tight is good enough.
Tom, MS II
2012 Phoenix Cruiser model 2552
KA4CSG
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| Re: Loud Exhaust [message #303032 is a reply to message #303012] |
Sun, 03 July 2016 23:40 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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This is a common problem on GMC's. Listen to Tom and Carl's recommendations above.
Exhaust manifold or manifold gasket problem.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: Loud Exhaust [message #303036 is a reply to message #303012] |
Mon, 04 July 2016 00:57 |
Bullitthead
Messages: 1411
Registered: November 2013
Karma: 5
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GET A NEW MECHANIC! Maybe he just doesn't want to work on it and is trying to scare you away. Do the gaskets...follow the knowledge available in this forum, past and present, and you will solve the problem correctly without collateral damage.
Terry Kelpien
ASE Master Technician
73 Glacier 260
Smithfield, Va.
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| Re: Loud Exhaust [message #303037 is a reply to message #303012] |
Mon, 04 July 2016 05:35 |
Chris Tyler
Messages: 458
Registered: September 2013
Location: Odessa FL
Karma: 7
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Senior Member |
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If you run the engine at night, warmed up and with the hatch off, you might be a ble to locate the leak. Be careful of the whirly bits though.Oh, and ventilate the coach.
Doubt it's a head crack.
76 Glenbrook
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| Re: Loud Exhaust [message #303041 is a reply to message #303012] |
Mon, 04 July 2016 06:59 |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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Senior Member |
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Jim Schulte wrote on Sun, 03 July 2016 20:04Had unit at local mechanic, and asked him to correct excessive exhaust noise thinking the doughnut was out. His opinion is the heads are cracked. I had him do a compression test and he stated compression in all cylinders is from 140 to 145 and the doughnut is OK. He said he thought there is a head crack at the exhaust manifold that does not extend into the cylinder on both heads. 1977 23ft Birchaven with 133000 mi and a 455. I do not understand cracked heads? I would suspect a bad exhaust manifold gasket and if so any recommendations on bolt removal and replacement of gasket. Jim
Jim,
I see you are not new here, but at least you are getting good answers. That is because this is the best place to get good answers.
You must have noticed that nobody here thinks it is a cracked head, and you have gotten answers that relate to millions of miles of experience.
I did miss seeing you come aboard in January, but as we are here now,
May the Good Lord bless this coach and all those that set forth within here.
Welcome Jim,
Matt
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
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| Re: Loud Exhaust [message #303044 is a reply to message #303012] |
Mon, 04 July 2016 08:33 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
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Senior Member |
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I suspect you guys are right and one at least of the manifolds will come off in more than one piece. Howeevr, I'd check the obvious first - are you sure you don't maybe have a muffler(s) with a hole in or rusted out?
--johnny
Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
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| Re: Loud Exhaust [message #303070 is a reply to message #303044] |
Mon, 04 July 2016 19:10 |
Bullitthead
Messages: 1411
Registered: November 2013
Karma: 5
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Senior Member |
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Don't forget about the choke stove gasket where it is bolted into the intake and the heat exchanger tube itself. Mine had developed holes in the tube and was leaking, and the noise was because the hot air choke was changed to electric and the tubes were broken off.
Terry Kelpien
ASE Master Technician
73 Glacier 260
Smithfield, Va.
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| Re: Loud Exhaust [message #303128 is a reply to message #303012] |
Tue, 05 July 2016 17:21 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
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Senior Member |
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Report back successes. Pictures are well received.
--johnny
Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
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