XJfan29

Ok XJ fans, I have a new symptom for you.

First off, here are the specs for heep:
98 xj 4.0 aw 4 4 door sport. Rough country 3 in lift. 31 inch mid tires (light off road only set up by jeep standards). Brown dog engine mounts and a new apn exhaust manifold.

I just got it back from the shop to fix the notorious cracked exhaust manifold. I replaced it with an APN thst will hopefully work. I also had the engine and tranmission mounts changed.

Here is my issue: the xj now knocks at cold temperatures. I cant tell how bad, it vibrates at idle causing small rattles in the interior panels and what not (this was expected with the new mounts).

once it is warm the knock goes away. Knocks under load and during idle. It takes less than 2 or 3 minutes for the knock to go away.

The xj has 162,000ish thousand miles. I have always used "full synthetic" oil. Too dark outside to check the oil level, but I will when it is light out.

My question: could this be the symptom of an improperly torqued exhaust manifold? What else could cause this noise besides the cam/lifter/rod/internal engine component?

This knock is so loud that I would have heard it before the manifold replacement. I didnt wait until the oem manifold leaked too bad to hear anything else.

Thanks!

98cherokee531

Mine is doing the same and I pulled the oil pan to find all rod bearings worn fairly even but 2 and 4 cylinders had more wear. Mine knocked at start up, and right around 2000 rpm that's it. Is it possible the previous exhaust leak masked the knocking sound?

XJfan29

I didnt really wait for the exhaust leak to get that far. I took it in because I wanted done before winter, and it was starting to get more noticeable.

Other people from 50ish feet away are giving me funny looks when I start it.

Theoretically, I guess the exhaust leak could have covered it up. But that is kinda far fetched. I would believe that the two issues are independent of each other yet occured simultaneously before I would think it had been this bad for a long time.

98cherokee531

Well all the easy stuff I'd check would be the flex plate cracked or loose, go through the manifold and check all fasteners, more easily just fire it up and run the throttle body with your hand. Try and pinpoint the noise by this method