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  #1  
Old 12-06-2014, 12:54 PM
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DanL DanL is offline
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Default My brother thinks I'm a genius! I'll take it.

My brother has been telling me about a bad knock in the engine of his daughter's 4.0L Cherokee engine. They haven't been driving it because of this, and yesterday we spent a little time looking at it.

It was a loud knock that could be hard - and felt - whenever quickly opening the throttle from idle. Once the revs were up, it didn't do it any more. It also made the noise when the engine first started and again on shutdown.

We spent some time trying to pinpoint the source of the knock and it sounded much worse from the top of the engine than the bottom, and seemed to be from near the back end.

There was an electrician here who was doing some work on the house wiring and he seemed to be a self-proclaimed genius on engines. He had my brother convinced it was a rod bearing going out ("I've seen it a hundred times", or something like that, he said).

Well, I've never heard a rod bearing failure so I didn't necessarily dispute that diagnosis but after the electrician left, I told Warren that I've learned to never assume the worst in any situation. We got to talking about it and I just sort of randomly said to him, "I wonder if it could be the flexplate-torque converter bolts?"

He crawled under the car and took the cover off the bellhousing and son of a gun, all 4 bolts were loose! He tightened them down and the noise was gone.

Now my brother thinks I'm a friggin' genius. I'm not; I just made a lucky guess. But I'll just let him think that for a while.
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Old 12-06-2014, 05:47 PM
John Kunkel John Kunkel is offline
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Quote:
Originally Posted by DanL View Post
He crawled under the car and took the cover off the bellhousing and son of a gun, all 4 bolts were loose! He tightened them down and the noise was gone.
Without red Loctite the noise might reappear.
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  #3  
Old 12-13-2014, 12:23 AM
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JVMopar JVMopar is offline
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Yup, heard that knock before. Also have heard cracked flex plates that knock or even squeak.

I agree. Always clean off the bolts and clean out the holes. Get all the oil off then Loctite them. Crank bolts and flex plate bolts.
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Old 12-13-2014, 06:45 PM
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DanL DanL is offline
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I actually recommended Blue Loctite. I wasn't there when he put it all back together so I have no idea whether or not he used any loctite at all, but he was warned.
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Old 12-29-2014, 01:49 PM
Skwerly Skwerly is offline
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Nice job! Lucky or not, your diagnosis helped the guy big time.
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