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Anyone else have the annoying YJ knock?. Sounds like a diesel on startup.? Gets quieter after warmup? Read some where it's a relatively easy fix,..shoulda saved it.
 

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Mine doesn't have it. Sounds like worn main bearings to me.
They are pretty easy to replace.
 

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Internet Owner
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Yes. They are a flat piece of metal that wraps around the crank shaft that are cut in half so they can be easily removed and replaced.
You simply open a beer, drink it as you drop the pan, remove the timing chain and trans, remove the crank stays, lower the crank shaft, tap the old ones out, put the new ones in, reverse process, fill with oil, drink more beer.
A little bit more details but you get the jest of it.
 

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Ya gott'a admit just changing bearings seems easy, and it sort of is, BUT..... you need to drop the crankshaft down enough to access the upper 'block' bearing halves. That entails the oil pan, timing chain, transmission and possibly oil pump. It can be done in-frame, but it's a hokey way of doing it and hap hazzard. The rod bearings on the other hand are easily accessible with the oil pan dropped, and are the bearings most likely to go first from wear. They have 'thrust pressure, where the crankshaft has circular pressures if you follow my meaning.
 

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The most critical part of the job was skipped, ensuring the part of the crank where the bearings are is in good shape, they are called the Crank Journals. Then measuring it super carefully, and getting the exact right bearing shells. Then using plati- gauge strips of the right size(colour) for your job, put a piece on each bearing, install crank, and torque to specificatioons. Then undo it, and pull crank back out, and measure the now squished to wider Plasti-gauge stips, and see if the clearance is correct. Also noot much point in doing just mains, while its apart do the Rod bearings to. Hope its just that, not something worse. Been there on this very issue, just that it wasn't a Jeep. Mine should have been warranty, but it is a crooked car company, so my son fixed it, and I 'assisted' ( slowed him down and asked a bazillion questions) It was better after.
 

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Sounds like a diesel on startup.? Gets quieter after warmup?
Make sure it isn't an exhaust leak before tearing your engine apart. The exhaust manifold studs are known break off and cause an exhaust leak but it could also be a crack anywhere on the exhaust manifold...sounds EXACTLY as you describe. With the engine cold, pressurize your exhaust system with a shop vac in blower mode connected to the tailpipe and spray soap solution on the exhaust manifold...look for bubbles.
 

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Make sure it isn't an exhaust leak before tearing your engine apart. The exhaust manifold studs are known break off and cause an exhaust leak but it could also be a crack anywhere on the exhaust manifold...sounds EXACTLY as you describe. With the engine cold, pressurize your exhaust system with a shop vac in blower mode connected to the tailpipe and spray soap solution on the exhaust manifold...look for bubbles.
You bring up a good point. I've seen many hairline cracks which after the engine warms up will expand the metal, virtually sealing off the cracks. I would check this before dropping the lower portion of my engine.
 
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