'98 from #@$%

I really just want to know if my fears are correct. So here's the story, I bought a 98 limited 4.0, AW4, 242 W/ 226,000. It has done well until a month or so ago, when it developed a knock. The noise is coming from the rear main seal area & bellhousing (Verified this). here is the strange part, It doen't do it all the time. it does it mainly at idle (cold or hot does not matter). It typically goes away with any increase in the RPM's, but not always. It doesn't use or lose any more oil that any other XJ I've seen & No water in the oil. I have comp. tested, AVG 150 PSI, also checked flywheel no cracks or lose bolts. SO am I on the hook for a motor or is there something I may be overlooking? Every bad bottom end I've seen knocks all the time. Any thoughts would be very helpful.

Re: 98" from #@$%

cracked flex plate or loose torque converter bolts.

edit.. sorry i see after the fact you check them.

Re: 98" from #@$%

Sounds like a sticky lifter to me.

Re: 98" from #@$%

Digger87xj said:

cracked flex plate or loose torque converter bolts.

edit.. sorry i see after the fact you check them.

Click to expand...

Digger87xj,

Sometimes the crack(s) in the flexplate (Drive Plate) are circumferential cracks under the spacer that can't be seen while the plate is installed, but only after the plate is removed.

You're on the right track mate.

Re: 98" from #@$%

Sidewinder CC said:

Digger87xj,

Sometimes the crack(s) in the flexplate (Drive Plate) are circumferential cracks under the spacer that can't be seen while the plate is installed, but only after the plate is removed.

You're on the right track mate.

Click to expand...

Agree.

Even after checking some flexplates with a camera probe it ended up requiring pulling the trans and torque converter to get where we could find the cracks.

Re: 98" from #@$%

I'll bet you could find cracks in the plate around the crank flange using Eddy Current NDT. Using a virgin plate as a standard and a cracked plate as a test specimen..

I watched it being used on aircraft wings. It could pick fly chit out of pepper.