4.0 engine knock

On my little 2.5 a bolt for the timing chain cover came loose, it clanked against the crank pulley. It sounded something like the clip you posted. it did take quite some time with a stethoscope and long screw driver to the ear to pin the noise to the timing chain area. Top and bottom of the engine are easy to access, but all the whirling pieces at the front of the engine makes it tricky to probe for the sound.

I tightened the cover bolts and put the timing chain kit on the shelf.
 
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Had a chance to get under the Jeep with a buddy and look things over a bit today. I hadn't noticed before but noticed today I realized I could see the timing chain a bit. And when I checked, it appears to be really loose. Possibly the source of the noise I am hearing.
 
Mine was like that too at 120K. According to the internet they never wear out. I used a Cloyes set from Rockauto.com, you can always find a coupon to save a bit off the $70+shipping. I think Cloyes is better than Crown but I'm no expert.

Edit: looks like $75.24 shipped with a 5% coupon
 
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Timing cover off. Still nothing glaringly bad, other than a loose timing chain.

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Mostly likely piston slap...you may have no real metal buildup from normal piston wear, leading to a little slap. When they sound like a ford diesel, then its a real probelm.
 
For less than $100 & a few hours, I'm going to replace the timing gear set & any exhaust leaks & hope it makes a difference.
My Avalanche with the 5.3 & almost 200k miles has piston slap for 10 or 15 seconds on cold mornings. So I'm familiar with it. This is far worse.
 
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Have you done what was suggested in post # 3?
I've checked for loose rockers. But don't know how to check if each cylinder is at TDC. Other than to pull the spark plugs & turn the engine over by hand with something sticking out of the plug hole to show that the piston is at the top of the stroke. But is that TDC or top of the exhaust stroke?
Plus a mechanic friend of mine said that with hydraulic lifters, they will always be under tension & be tough to feel them being loose.
 
I've checked for loose rockers. But don't know how to check if each cylinder is at TDC. Other than to pull the spark plugs & turn the engine over by hand with something sticking out of the plug hole to show that the piston is at the top of the stroke. But is that TDC or top of the exhaust stroke?
Plus a mechanic friend of mine said that with hydraulic lifters, they will always be under tension & be tough to feel them being loose.

Use the EO/IC method to check each valve. Your mechanic friend is correct if there was nothing wrong with your engine, but that is not the case here.
 
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Wow, that looks pretty bad. Excuse my ignorance but what will you do in this situation? Grind the crank and replace the bearings? Rebuild the entire engine?
I thought about just replacing all the rod bearings and buttoning it back up. But recently found a guy who says he will do it for $1500, parts and labor. So I think I'm going to rebuild it.
 
That bearing is too far gone to just replace the bearings. The bearing journal on the crank is ruined. You’re doing the right thing by rebuilding the engine.
 
Tore it down in the Jeep today. We were going to pull it whole, but my partners hoist had leaked. Took about 3 hrs to get it down to the block, Pistons & rods are out. He's going to refill the jack on his hoist and we'll pull the block/crank tomorrow.
The last pic is the weird oil still in it. Like Rotella diesel oil or something. Any chance this is why the rod bearing spun?

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