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Piston Slap?

That sounds worse than piston slap. If you cracked another piston on the same cylinder, you probably have a damaged rod. Could be valve train related too. Pull the rocker cover off and see if you can pinpoint it to a single rocker.
 
If you cracked another piston on the same cylinder, you probably have a damaged rod.

Not entirely sure what you mean, but it's an entirely different motor from the first one. I've heard the NVH stuff they did causes the number 5 piston to crack.
 
Jeep is a 97. Cracked the #5 piston in the original motor at about 135k. New motor went in; 98 from the junkyard with 88k. Got about 168k on the clock now (about 121k on new motor) and this happening.

Also, I can only hear it when it is relatively warm. It seems like the warmer it is, the more noticeable it is. In the video I was over 210 on the temp gauge and that is the loudest its ever been.
 
Also, I can only hear it when it is relatively warm. It seems like the warmer it is, the more noticeable it is. In the video I was over 210 on the temp gauge and that is the loudest its ever been.

Hold on for a second! I've had bad "lifter noise" for the last two years that was driving me nuts. It was intermittent but always got worse and worse the hotter it got. It was definately louder than any lifter I had heard and I wondered if it was worn wrist pins or rod knock. I finally came across a post on NAXJA where someone talked about excessive carbon buildup on valves or piston tops causing some horrible noises that sounded like a bad lifter or rod knock. I finally fixed the problem with two cans of Mopar Combustion Chamber Cleaner hot-soaked through the throttle body on seperate days. No more "clatter/knock" that I've been living with for the last 2 years (yes, 2 years of listening to the damn thing tick away like a bomb).
Heres a quote from an external site that also helped me out. This guy recommends using ATF down the carb throat (old mechanics trick), but I just played it safe and used MCCC:

Sometimes, a carbon knock will sound just like a rod knock. It will sound like it's ready to throw a rod. I can't even count how many times I have fixed this with about half a bottle of transmission fluid.

Start the engine; remove the air cleaner; rev the engine up to about 2500 rpm and start slowly pouring the transmission fluid down the carburetor throat. Don't let the engine die. (if it does, you might have to pull & clean the plugs, then resume the procedure). Pour the XMF fast enough to lug the engine down.

Voila -- no more knock. Gone for good. This apparently happens when a little piece of carbon breaks off inside one of the cylinders or something..... but I've fixed 'em numerous times this way when I thought I had lost a rod bearing.

This was the post on NAXJA that got me started:
UPDATE:

Turns out that it was not a cracked manifold problem, or anything that an oil additive used in the oil could fix.

As I was growing more pissed off at my 4.0 as the days went on, (been ticking since Oct 07) and after a straight year of MMO, type F ATF, cans of seafoam in the oil, (sometimes as low as 3 qts of normal oil, and a cluster**** of additives and changing my manifold... nothing was close to improving the issue.

Last week I bought another can of seafoam, and instead of throwing the whole can in the oil, I sucked the whole thing into the intake. Took about a minute to use the whole can. I let it sit a half hour. When I fired it up, it didnt tick at first, but when I went to rev the engine to start clearing the smoke, it went "tap-tap-ta" and it was gone. As soon as the smoke cleared, I drove around for a half hour in silence. I can't tell you how many times at red lights I had to look at my tach to see if the engine was still on.

It has been 2 weeks, and I have not had my engine tap since I used one can of foam in the intake.

All I hear at idle now is my injectors and my noisy HB.

Question: What was ticking that mimmicked a lifter tap? Im guessing carbon buildup on valves...anyone?
 
I was chasing a problem a while ago in my 4.0L. Non existent when cold and got louder when warm. Replaced the lifters twice. Installed a new cam with no relief. Finally #5 piston let go and took up residence in the oil pan. I don't contribute min to a problem with the NVH block, but hydro locking my engine while off road.

I think your best bet is to get the engine warmed up, shut it down then pull the valve cover and see if you can find the source of the sound and go from there.
 
This would make a lot of sense. I just started driving my Jeep to and from class everyday in the cold weather instead of walking. It's probably a 2 minute drive at most. Doesn't this kind of driving increase carbon build up?
 
try the MCCC. I thought my engine was toast until I used the 2 cans in there a few weeks ago. I've put on over 2k kilometres in the last week since using the MCCC and havn't heard a peep out of the engine, runs like new.

well it is certainly worth a shot at this point. I changed the connecting rod bearings last weekend and it is still noisy as hell. Where do you get this magic mopar cleaner? dealer only item I am assuming.
 
well it is certainly worth a shot at this point. I changed the connecting rod bearings last weekend and it is still noisy as hell. Where do you get this magic mopar cleaner? dealer only item I am assuming.

yeah get it at the dealer or, like someone else said, just run a can of seafoam through the vacuum line from you brake booster.
 
I changed my rod bearings as well trying to chase my noise down. If you haven't already used a stethoscope, I would start there. If you track it down to the valve train, you could pull the cover, and back off the nut on each rocker one at a time, and see if the tone changes.. (with the engine running of course Parts stores have clips that plug the end of the push rods to keep oil from shooting out.
 
Seafoamed it. Runs better, idles smoother, but still this:



I went wheeling again and as the engine got hotter it was much more pronounced. One time I turned it back on after letting it cool for a minute and it was stumbling. Not bad, but it was running noticeably rough. Any new ideas?
 
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