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[GMCnet] Motor Knocking Part 2 [message #204185] Tue, 09 April 2013 18:39 Go to previous message
Richard Waters is currently offline  Richard Waters   United States
Messages: 4
Registered: February 2004
Karma:
Junior Member
Continuation of my tale of woe:

I consulted Ken, Emery and Matt on what to do about that. Matt wrote me and
said, "It is my experience that the primary leakage of coolant into lube oil
is across the head gasket body. If there was a combustion seal failure, it
would have been evident in the coolant. (It makes it muddy pretty fast.)
That being the case. After you have finished looking for external leaks and
if you found none, try "pulling" on the cylinder head bolts. This is a PITA
operation because the cylinder head covers have to come off. Get that all
that stuff on top cleared away and find a flexible bean torque wrench.
(Yes, the cheap kind and there is a reason). Olds spec for final torque is
85#ft. Pull on each bolt at that level, and if it moves keep pulling to 85.
(The pattern is not important.) If they don't move, (this is where the beam
wrench is important) make a mental note of where in space the end of the
pointer is, and crack the fastener back off. Now, pull it up again and I
will bet you that you get a few more degrees on that pointer. (Now, exhale
and hope that was the problem.) If you gain fastener rotation on any, you
will probably gain it on all. The reason you had to back them up is simply
that the threads stick. That "break-away" torque often exceeds the
installed torque even though the fastener has lost tension. What has
happened is the head gasket material has what is called creep. That means
that the fasteners their lost tension that was compressing the gasket body.
Now, you are getting that tension back. That tension recovery could easily
be enough to close off an internal coolant leak."

Since I am sure Matt knows what he is talking about, I pulled both rocker
covers and checked the torque tension per his suggestion. The driver side
was inconclusive. I couldn't tell much except that the bolts seemed to be
torqued to 85 and when I backed them off and retorqed them, there didn't
seem to be change in the position of my 50 year old beam torque wrench.
Then I did the same to the passenger side. All of the bolts, except the one
next to the center exhaust port, snapped (they moved) when I approached 85
foot pounds. So could it be that the head on the passenger side was not
torqued to spec during rebuild? I was discouraged that the builder
apparently didn't torque the passenger side to spec, but that perhaps I
sealed the leak. In addition, per Emery's recommendation I drained, flushed
and refilled the coolant and added Bar's stop leak. So I put everything back
together and got ready to leave on our trip. I ran the engine a few times
after that without incident. Then the knock started the day before we were
leaving.

Ken was nice about it, but I am sure he figured I messed something up when I
was in there checking the torque. I had to agree, having made more than my
share of mistakes repairing stuff, so I didn't feel too bad about taking the
covers off again. I'm now an expert at taking those things off. Sadly, I
still can't find where the knocking sound is coming from and nothing seemed
to be molested or left behind by my previous work. So today I pulled both
rocker covers off and couldn't find anything loose or anything in there that
wasn't supposed to be there. I also ran the engine and listened to each
rocker with my stethoscope and couldn't hear anything related to the knock.
Of course I am a novice at listening to engine noises. I learned that that
you can run a 455 for a short time with the covers off and not make a mess.
I put it all back together, with no plan in mind on how to fix the problem.
Some will say it's time for another new motor. If that's the case the GMC
will have to become a yard ornament for a while.

Any ideas, anyone what could be knocking? It started suddenly and is pretty
loud. I have not driven it since it started and have probably less than 10
minutes total time running with the knock.

Richard

SE Michigan

www.PalmBeachGMC.com







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