fj60 newbie here, video of engine knock/tap. any help pinpointing appreciated

zia

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Hey guys I have a 1988 that I am working on finding the knock/tap source. I have chased it down to first cylinder making that noise by unplugging each ignition wire. when first cylinder is unplugged, the sound goes away. so I removed the valve cover hoping to see any obvious issue but I don't. Maybe you guys can help me out. valves? rings?

many thanks!

 
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You could try to do a compression test and see how #1 is. Your knock is not likely a ring problem but a failed rod bearing or maybe something up with the wrist pin. Compression test is quick and easy. Then I’d drop the pan and have a look
 
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Seth is right. I suspect a spun bearing or something like that. If you catch it now before it grenades you could possibly replace the bearings while the engine is in the truck and keep on going for a good long while. But you’ll have to test it and take a look to know for sure. I think it’s in the lower block.
 

zia

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ok thank u guys for great advices, going to buy a compression tester now and get back with result
 

zia

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ok just tested the 1st cylinder. 120-124psi. the engine is at 214k and never been rebuilt. what do u think?
 
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ok just tested the 1st cylinder. 120-124psi. the engine is at 214k and never been rebuilt. what do u think?
What are the other cyls at? My only thought was if the bearing had fully failed that piston travel might be limited and thus lower compression. But if the bearing is still in place but coming apart it might not show anything in a comp test.
 
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A bad bearing will not show anything on a compression test. That hard hammering sound is almost certainly a failing connecting rod bearing. If you stop driving it right now you might be able to get away with just replacing the bearings (but the crank probably has some damage).
 
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A bad bearing will not show anything on a compression test. That hard hammering sound is almost certainly a failing connecting rod bearing. If you stop driving it right now you might be able to get away with just replacing the bearings (but the crank probably has some damage).
I was thinking if the bearing/pin were effected enough to impact piston travel...even a small amount would affect effect compression. Either way the pan needs to be dropped.
 
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That doesn’t seem too low for those miles. But really you need to compare that cylinder to the rest of them. If they’re all in the 120-130 range then that is normal compression for an engine with that many miles. But if that one is 120 and the others are at 150-160 then I’d say you’re on the right track. After checking the others I’d drop the oil pan and check your bearings and wrist pins.
 
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I was thinking if the bearing/pin were effected enough to impact piston travel...even a small amount would affect effect compression. Either way the pan needs to be dropped.
Bearing tolerance is like .002" at the limit for these engines. If you have 10x that clearance (0.020"), you're going to get severe bearing noise - but that's still only the thickness of 5 sheets of paper. That's not going to effect compression a measurable amount. Now it might be possible for complete bearing failure (shell complete gone) to cause a measurable decrease in compression. But at that point the engine will be hammering so loud there will be no point to do a compression test.
 
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will do that later today and let u guys know what I find. thank you all for your help :)
Do you have a factory service manual? It will help you tremendously with measuring tolerances and getting torque specs right.
Cruisermanuals.com
Free pdf files^
 

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