Home » Public Forums » GMCnet » [GMCnet] Noise in the engine
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 Re: [GMCnet] Noise in the engine [message #277317 is a reply to message #277305] |
Tue, 05 May 2015 12:38   |
Tilerpep
Messages: 404
Registered: June 2013
Location: Raleigh, NC
Karma: 7
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Senior Member |
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Asking more on the whole thread, and specifically Dwayne's comment about flex plates:
I took my coach to an experienced truck mechanic friend just last week for a noise that only happens after driving coach to full operating temp, then turning it off, and then restart it from two to maybe twelve minutes later (hot restart).
He said he had only ever heard a noise like that one time, a guy had a Buick that they eventually found a cracked flexplate.
So, if this is a correct direction for me - does the hot re-start tell me anything? And can I see potential cracks or loose bolts from an access panel or anything, or is tearing it down the only way to know? I have debated an engine oil analysis to learn more engine internal scenario, but then this thread came up!
1975 Glenbrook, 1978 Royale rear bath
Raleigh, NC
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| Re: [GMCnet] Noise in the engine [message #277320 is a reply to message #277317] |
Tue, 05 May 2015 13:03 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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Senior Member |
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Tyler, the noise a loose flexplate makes sounds like a broken crankshaft.
Heavy knocking. Diagnose by removing the starter, then the sheet metal
shield. This exposes the attachment bolts. Turn engine by the large nut on
the fan end of the crankshaft, and check the dampener while you are there.
They can mimic this noise. Turn crank until torque converter bolt is
exposed. Remove one and carefully inspect it. It should NOT BE THREADED
upon its full length. The correct bolts will have a large shouldered head,
and the upper portion will have a precision shoulder that is slightly
shorter than the thickness of the flexplate. Check also that the bolts DO
NOT bottom in the converter lug. Look carefully for any signs of bottoming.
Use a strong light source and look in the hole in the torque converter lug.
If it is shiny in the bottom of the hole, the bolts are bottoming before
the flexplate is tightly against the lugs. It will knock like mad if you
find this condition.
Jim Hupy ( aka. the taller brother)
Salem, Oregon
On May 5, 2015 10:39 AM, "Tyler" wrote:
> Asking more on the whole thread, and specifically Dwayne's comment about
> flex plates:
>
> I took my coach to an experienced truck mechanic friend just last week for
> a noise that only happens after driving coach to full operating temp, then
> turning it off, and then restart it from two to maybe twelve minutes later
> (hot restart).
>
> He said he had only ever heard a noise like that one time, a guy had a
> Buick that they eventually found a cracked flexplate.
>
> So, if this is a correct direction for me - does the hot re-start tell me
> anything? And can I see potential cracks or loose bolts from an access panel
> or anything, or is tearing it down the only way to know? I have debated an
> engine oil analysis to learn more engine internal scenario, but then this
> thread came up!
>
>
>
> --
> 1975 Glenbrook
> Raleigh, NC
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> GMCnet mailing list
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| Re: [GMCnet] Noise in the engine [message #277322 is a reply to message #277321] |
Tue, 05 May 2015 13:32 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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Senior Member |
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The noise is severe enough that you might exclaim " OH MY GOD, SHUT IT OFF,
QUICK." Hard to believe loose flexplate can make that much noise, but it
can.
Jim Hupy
On May 5, 2015 11:27 AM, "Tyler" wrote:
> Great info, thanks Jim. How urgent is the next question - can I use it and
> get under there to check flexplate soonish, or is this a "don't drive it
> till ya check it". Currently it is totally silent on cold start, and
> silent within 30-60 seconds of hot restart. It whacks pretty solid
> sometimes, but
> I have never heard a broken crankshaft to compare!
>
>
> --
> 1975 Glenbrook
> Raleigh, NC
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
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| Re: [GMCnet] Noise in the engine [message #277357 is a reply to message #277305] |
Tue, 05 May 2015 23:12 |
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Jerry Sitzlar
Messages: 206
Registered: February 2013
Location: Lenoir City, TN
Karma: 4
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Senior Member |
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My 455 developed a noise that sounded like a rod bearing. The noise almost went away when number 7 spark was grounded. I started thinking rebuild. After the oil analysis came back very good, I already knew I needed mufflers and pipes, after replacing those the muffler shop said I had leaking exhaust manifold gaskets. After removing the manifolds, I found the LH manifold to be cracked. After a new used manifold and a set of Remflex gaskets, and a couple of donuts later, the engine no longer has that knocking sound.
My grandson's Jeep Wrangler had the exact same thing. Rod knock sound but turned out to be a cracked exhaust manifold (common on Jeeps).
Sorry, Chuck's version was shorter and to the point.
Jerry
Jerry Sitzlar..... 77 Eleganza II, Twin bed, dry bath...... Lenoir City, TN (near Knoxville)
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