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03-08-2008, 11:34 AM
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#1
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Member
Join Date: Jul 2007
Posts: 32
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Hello everyone. Been awhile since I Have posted, but need some help. I have an engine noise that sounds like a rod knock, but...
At cold start up = no noise. (Oil Pressure 50 PSI) Accelerates fine. After reaching normal temp (195 degrees, Oil 25PSI) Noise starts, as if a rod knock. I can accelerate and the noise goes away. I can let up on the gas, no noise. It seems to show up at a certain range of constant RPM. I have noticed at Idle the oil pressure about 5 PSI. Anybody had similar problems , or know what my problem is?
Thanks,
Randy
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03-08-2008, 11:34 AM
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#2
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Member
Join Date: Jul 2007
Posts: 32
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Hello everyone. Been awhile since I Have posted, but need some help. I have an engine noise that sounds like a rod knock, but...
At cold start up = no noise. (Oil Pressure 50 PSI) Accelerates fine. After reaching normal temp (195 degrees, Oil 25PSI) Noise starts, as if a rod knock. I can accelerate and the noise goes away. I can let up on the gas, no noise. It seems to show up at a certain range of constant RPM. I have noticed at Idle the oil pressure about 5 PSI. Anybody had similar problems , or know what my problem is?
Thanks,
Randy
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03-08-2008, 03:29 PM
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#3
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Moderator Emeritus
Join Date: Jan 2000
Location: West Palm Beach, FL. USA
Posts: 27,704
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I'm surprised your oil pressure drops all the way from 50 to 25 as it warms up. And way low at idle. Wonder what are other folks seeing for warm oil pressures on a 454?
By the way, how old and how many miles on that beast?
__________________
Gary Brinck
Former owner of 2004 American Tradition and several other RVs
Home is West Palm Beach, FL
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03-08-2008, 04:42 PM
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#4
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Member
Join Date: Jul 2007
Posts: 32
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The speedometer has a reading of 110K, but the motor had been rebuilt by a previous owner at 60K. Apparently, the oil was drained but not replenished and driven dry. I assume that the owner did it himself, since I have the reciept for parts. I was a little concerned about the oil pressure myself, maybe some other folks might have some input. By doing a web search, some people have reported a knocking sound from the exhaustmanifold. I have replaced the exhaust manifold gasket, but not the donut. Could a blown donut gasket, from the manifold to the exhaust pipe give me the same symptoms?
BTW it is a 91 Coachmen, 454.
Thanks,
Randy
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03-09-2008, 04:19 AM
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#5
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Senior Member
Winnebago Owners Club
Join Date: Feb 2007
Location: Jacksonville, FL
Posts: 235
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<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by ROHawkins:
Hello everyone. Been awhile since I Have posted, but need some help. I have an engine noise that sounds like a rod knock, but...
At cold start up = no noise. (Oil Pressure 50 PSI) Accelerates fine. After reaching normal temp (195 degrees, Oil 25PSI) Noise starts, as if a rod knock. I can accelerate and the noise goes away. I can let up on the gas, no noise. It seems to show up at a certain range of constant RPM. I have noticed at Idle the oil pressure about 5 PSI. Anybody had similar problems , or know what my problem is? </div></BLOCKQUOTE>
I had a very similar problem in a late 80's Chevy V6. It turned out that the main bearings were shot and as the engine warmed up it would let the warmer and thinner oil just flow by, lowering the overall oil pressure. I'm not much of a mechanic... wish I could explain it better.
__________________
Ron, Joan
2005 Itasca Sunova 34A
2004 Jeep Grand Cherokee Overland
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03-09-2008, 05:00 AM
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#6
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Member
Join Date: Jul 2007
Posts: 32
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How would one pull a motor out of a motorhome? This is a 1991 27'Coachmen, with the doghouse enclosure.
Thanks,
Randy
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03-09-2008, 09:02 AM
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#7
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Senior Member
Join Date: Aug 2002
Location: Little Valley, NY (Snow Country)
Posts: 161
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<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by ROHawkins:
How would one pull a motor out of a motorhome? This is a 1991 27'Coachmen, with the doghouse enclosure. </div></BLOCKQUOTE>
I would think you have to pull the grill and the radiator. Then out thru the front.
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03-09-2008, 11:05 AM
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#8
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Member
Join Date: Oct 2001
Posts: 86
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<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Posted March 08, 2008 09:42 PM Hide Post
The speedometer has a reading of 110K, but the motor had been rebuilt by a previous owner at 60K. Apparently, the oil was drained but not replenished and driven dry </div></BLOCKQUOTE>
I'll bet your mains are gone if it was run dry. Next will be a rod going out , most likely when is is the least convenient
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03-09-2008, 12:03 PM
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#9
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Senior Member
Join Date: Dec 2007
Location: Blairsville,GA
Posts: 257
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It's possible too that when they put in the rebuilt motor, it was not properly lubed when it was first started. If the oil pump was not first primed, it could have been running on dry bearings when it first started, most professional builders use a grease on the bearings to help prevent this, but the installer has to also spin the oil pump to make sure everything is lubricated well and the oil pressure comes up quick. This is usually done with a drill and a old distributor used to turn the pump connected at the bottom. I have also seen the distributor left too loose at start up and pop out of the oil pump, causeing the oil pressure to go to 0, but the engine still run. (caught that one too late, ate the rod bearings in less than a minute)
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03-09-2008, 01:46 PM
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#10
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Member
Join Date: Jul 2007
Posts: 32
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Everybody and those that still have more info, Thanks for your help. If I have to rebuild, was thinking about doing away with the ECM and keeping it simple. Anybody have any ideas on this thought.
Thanks again,
Randy
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03-09-2008, 06:55 PM
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#11
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Member
Join Date: Feb 2007
Posts: 53
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Sorry Randy,
It's a main bearing gone (the others are probably out of tolerance too). That 454 should have at least 15 lbs at a hot idle even in the summertime. You shouldn't run it anymore. Even at idle speed it will cause all kinds of damage (especially unrepairable block damage) if it lets go. Even if the rod stays on the crank, there is usually solid and pulverized babbitt from the bad bearing(s) floating around the crankcase. It's great when it's used as a bearing material in the correct place; babbitt is is like sand when it gets where it isn't supposed to be. Best of luck.
sparetire
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03-09-2008, 07:00 PM
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#12
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Senior Member
Monaco Owners Club Workhorse Chassis Owner
Join Date: Aug 2002
Location: Clovis, CA, USA
Posts: 13,149
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A guy on RV.net posted pics of pulling his engine and putting it back in. He did it thru the Doghouse.
He used an engine hoist on plywood in the coach.
Rv.net is DOWN now or I tell you who it was. Don't know if or when RV.net is coming back up. It's been very slow the past week.
__________________
2004 Monaco La Palma 36DBD, W22, 8.1, 7.1 MPG
2000 LEXUS RX300 FWD 22MPG 4020 LBS
Criticism is easier than Craftsmanship
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03-10-2008, 04:34 AM
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#13
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Member
Join Date: Jul 2007
Posts: 32
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If it is a main bearing, wouldn't the noise get louder under a load? At about 55mph, I can accelerate and the noise goes away.
Thanks,
Randy
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03-10-2008, 05:13 AM
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#14
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Senior Member
Join Date: Jan 2008
Posts: 197
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Actually, from your description, (noise goes away under load), it sounds like a rod bearing to me. That can also cause a decrease in oil flow thru the crankshaft.
Ron
__________________
2003 GulfStream Ultra Supreme 33' Class A
Ford Edge toad
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