Rattle from front of engine under load

[BCParker]

title says most of it.

97 4.0 auto, ac, 160,000

I get a loud rattle/knocking noise from the front of the engine compartment.

noise happens only under load around 1700-2000rpm.

I have checked, nothing obvious caught in belt or fan,

belt was glazed on smooth side, great condition on ribbed side.

replaced belt and idler pulley.

with belt off, no noise., however, 1/8th to 1/4 inch wobble visible in the crank pulley. no scuffing marks on timing cover.

I'm wondering if my symptoms could be related to a bad crank pulley (the rubber looks ok but it is original) or possibly the timing chain scraping inside the cover.

any ideas appreciated.

Thanks- B

 

[badron]

Check motor mounts and trans mount. R+R if needed.
Check slush converter bolts AND flex plate for cracks. If bolts are lose. Insure the threads are not badly worn. R+R bolts if needed. Use lock tight red on bolts. R+R flex plate if cracked.
Check for cracked poop manifold. R+R If needed.
This covers about 80 present of knocking in XJs. LUCK

A good bud is had to find.
Even harder to lose.
WORK SAFE.

 

[nwjohn]

The Bottom pulley shouldnt move back and forth hardly at all (wobble). The serpentine belts will make a lot of noise if the pulley is wobbling , i have heard them sound like a rod bearing going out .
Look at your bottom pulley its probably going bad, the rubber between them gets old and deteriorates.
got mine from napa, wasnt very much around 50 bucks or so and just a little time , not to hard to change at all.

John