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Jeep Wrangler YJ
YJ General Discussion
Engine Knock
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<blockquote data-quote="Wayne R" data-source="post: 437163" data-attributes="member: 20451"><p>Thanks for all the replies! I ruled out rod and main bearing as being the cause due to replacing them. From the way everything acted, it seemed to be the likely cause. The one main bearing had a deep dig (#5 position), but did no damage to the crank shaft. For the most part the rod bearings looked good when I changed them, a little wear. One strange thing happened when I tried to roll the #2 piston/position main bearing (same piston that I believe has the loud knock) the new bearing got stuck on something and would not roll in. I rolled the old bearing back in with no problem. The crank shaft looked fine, and I used plastigage to measure tolerance and all was correct. I did use heavier oil, but it had no effect. When I had the oil pan off to replace the bearings, I did look at the pistons as good as possible, and there didn't seem to be damage. When the rod bearings were off I tried to feel if there was any play in the pistons and there didn't seem to be. Also, I agree with the piston slap going away as the engine warms, that's why I am at a loss. When it is cold it takes awhile to start knocking, and when I took it into the woods where it was cool it wasn't as loud. I feel like it is broken piston skirt or valve problem, but once again don't want to make expensive repairs without picking people's brain for input because I have hit a wall. By the way... the engine only has 72K on it, but it seems like someone replaced it before I bought it which was 19 years ago. Not a hint of problems up until now. The engine does lack power. There was a small amount of shavings in the oil pan.</p></blockquote><p></p>
[QUOTE="Wayne R, post: 437163, member: 20451"] Thanks for all the replies! I ruled out rod and main bearing as being the cause due to replacing them. From the way everything acted, it seemed to be the likely cause. The one main bearing had a deep dig (#5 position), but did no damage to the crank shaft. For the most part the rod bearings looked good when I changed them, a little wear. One strange thing happened when I tried to roll the #2 piston/position main bearing (same piston that I believe has the loud knock) the new bearing got stuck on something and would not roll in. I rolled the old bearing back in with no problem. The crank shaft looked fine, and I used plastigage to measure tolerance and all was correct. I did use heavier oil, but it had no effect. When I had the oil pan off to replace the bearings, I did look at the pistons as good as possible, and there didn't seem to be damage. When the rod bearings were off I tried to feel if there was any play in the pistons and there didn't seem to be. Also, I agree with the piston slap going away as the engine warms, that's why I am at a loss. When it is cold it takes awhile to start knocking, and when I took it into the woods where it was cool it wasn't as loud. I feel like it is broken piston skirt or valve problem, but once again don't want to make expensive repairs without picking people's brain for input because I have hit a wall. By the way... the engine only has 72K on it, but it seems like someone replaced it before I bought it which was 19 years ago. Not a hint of problems up until now. The engine does lack power. There was a small amount of shavings in the oil pan. [/QUOTE]
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Jeep Wrangler YJ
YJ General Discussion
Engine Knock
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