Knock knock...who's there?
 

Ok so i just got this 01 Cherokee with the 4.0. when i start it up its got a horrible knock. i pulled the valve cover to check rockers all tight and started with it off and everything was in working order there, so i ruled out lifters. its a pretty gnarly knock when its started it calms down a little after warming up but doesn't go away. oil pressure is great when started over 40 then after driving its in between 15-20. I've got some aggressive tires on it so its hard to tell if its still there while driving but stopped or low speeds its there. i have a video but no idea how to put it on here (any help). so after all my reading I'm pretty sure its got to be rod bearings or the flex plate. but then again would the flex plate get quieter or stay the same? any help fellow jeepers?

change oil yet? mine did that after purchase, assuming fuel rich oil

i did new oil / o2 sensor/ cat converter / muffler .. it went away instantly ..But it sounded exactly like a video of a rattling flex plate on here

i use photobucket to host pics/vids .. easy to click & copy the URL

yeah brand new oil... i know it has a small exhaust leak right before muffler but i definitely hear it from motor. ill photo bucket in a lil bit to get a vid up.

What brand of oil filter is on it?

Automatic trans?

My daughter's '87 Renix DD has the same knock.

It used to rattle only on startup for about 3 seconds until the oil pressure came up fully. Some posters on here call that a dry start. It appears to be some what common.

I took her Jeep to 2 different mechanics on Thursday. One said he thought it sounded like cam bearings were worn, as the sound actually comes from mid-block. I initially thought, like you, that it came from the rocker area.

The other one said it is just getting noisier from wear. I still have adequate oil pressure, and there is plenty of oil flowing in the upper area. His advise was just to drive it like it is. Nothing was getting hurt. Someday, of course, I'll have to rebuild it.

I use 10W-30 Mobil 1 with a Wix filter.

Jeep will use a quart in about 6,000 miles. It has 215,000 miles on the original engine.

Lets see if this video works.

http://i1270.photobucket.com/albums/...127_153310.jpg

Its an auto and its a fram oil filter.

Get rid of the Fram filter and put on a quality filter like Wix

http://minimopar.knizefamily.net/oil...reference.html

not to sound like an idiot but what will that help with? noise? or pressure?

Possibly both. Trust us. Change just the filter. Fram is notorious for coming apart inside. Nothing to lose and everything to gain.

I'll give that a try.


any other suggestions?

Possibly loosening flexplate bolts if it's an auto trans. Do the filter first.

Yes, do the filter first. If that doesn't solve it, try this:
https://www.cherokeeforum.com/f51/ho...ocking-125547/

When looking over the flexplate will I be able to tell if the bolts are loose by hand?

If you're at the point of having the inspection cover off to look at the bolts, you might as well take out the 4 bolts, clean them up and reinstall them with red Loctite.

But if there is a flexplate knock, at least one of them will be loose. Maybe not to the point of being taken out by hand but definitely easily with an open ended wrench.