letsgomuddin

So with 255k miles, I expected a few quirks and mechanical issues, even with the mostly bulletproof 4.0. So here's my issue. I have what by all means appears to be a rod knock. Louder than a lifter, crankshaft speed, and using a stethoscope is loudest in the pan. I'm used to rod knocks working on antique British cars for a living, but this one acts very odd. For the first few seconds of starting it it makes no noise at all. At idle it's loud whether warm or cold, though it is louder cold. But if you load it via power braking or accelerating, the knock goes 99% away! Usually rod knocks get worse under load and don't go away. Anyone have any insight before I pull the pan?

Turbo X_J

Automatic?
Check torque convertor to flex plate & flex plate to crankshaft bolts.

letsgomuddin

Sorry, should have mentioned that, it is an auto, just checked the torque converter bolts yesterday, good-n-tight! Not in the mood to pull the tranny to check the flex plate to crank bolts, can't imagine why?!

winston427

Yep sounds like a broken flexplate. Pull the inspection cover back off the bell housing and look toward the center of the flexplate. You will see the cracks coming from the center.

letsgomuddin

Checked the flexplate while I tightened the TC, no cracks visible!

winston427

Mine were almost microscopic but the flexplate was completely separated in a star pattern around the crank bolts. Knocked like hammers in a steel drum while idling but almost unnoticeable when accelerating. Fixed it myself in the driveway.

letsgomuddin

Nice, I guess at lunch tomorrow I'm going to clean it off good and check it out closer. Gonna have to clear out a weekend to pull the trans and check it out.

letsgomuddin

Must be an issue with all gens of XJ's then? Heard about it on earlier ones, just not the real late ones like mine.

winston427

There will probably be more of it happening with the later models as they get more age and miles on them. The flexplate design did not change and it is still just a thin piece of stamped sheet metal.

All I can say is make sure you have a good transmission jack for the sake of safety. Took me about 8 hours to pull the trans, change the flexplate, and reinstall the trans. All with basic hand tools and a lot of profanity.

letsgomuddin

I have a hoist at my folks place, makes things alot easier! Tranny jack too, just gotta find the time! Any source other than the dealer for a new flexplate? Like NAPA or something?

winston427

I got lucky and found a XJ in the junkyard that some nice soul had already pulled the trans out of and left the flexplate. Zip bang 6 bolts and $15 out the door.

winston427

I just looked on rockauto.com and there is no listing.

letsgomuddin

nice, bet the dealer wants an arm and a leg too

winston427

Found these but no one shows an 01, only up to 00. Don't know of any changes made to the flexplate in 01 but why we expect the last year to match any damn thing.

http://www.partsgeek.com/catalog/199...lex_plate.html

http://m.autopartswarehouse.com/deta...321691310.html

http://www.drivewire.com/vehicle/200...ee/flex-plate/

Turbo X_J

You can also check:
http://car-part.com/