Ye Ol' Cherokee

hi guys, I have a 1998 Cherokee Sport 4.0 with 140,000 miles. I have had the Jeep for 10,000 miles now. I always use castrol high mileage blend with either a napa gold filter or purolator pureONE when I do or changes. when I put it in the Jeep I started to notice a light knock from the oil pan. I'm not sure if it's from the oil or if I just didn't notice it before, but i have done 3 oil changes since with the same oil

some details: when I first start it cold you can't hear it, but after about 15 seconds you begin to hear it, and it does not go away at any temp. sometimes it is louder than others. When i accelarate, up til abouy 1800 rpm, i hear it speed up a bit, but im thinking that might not be the same noise. And at 3000 rpm and higher, it sounds like a sewing machine, but i heard that is normal, correct me if im wrong.

the oil pressure at cold starts out at like 50, never goes higher than 60, and after its been running for a long while and is hot, the idle sits at about 10-11 psi. I still have to check it with a mechanical gauge though.

The noise is loudest by the front wheels and if you stick your head underneath, but can also be heard in the cabin, and very lightly from the top of the engine. Its not very loud, so if you don't listen for it, you might not notice it, so it doesn't seem to be that bad.

there is no real loss of power, but I've never driven another jeep to compare it to.

I have audio files, which have the sounds that I am hearing from underneath, but the site won't let me post them I guess because they are the wrong file type. if someone could tell me how to post them to here that would be great, or f you would consider letting me email them to you so maybe you could help me

jj1562

Look on YouTube for, "cherokee flexplate loose" see if it's the same sound

F1Addict

Assuming it's an automatic, of course. Best to fill out the rest of the info in your profile so we don't have to assume

Ye Ol' Cherokee

Yea, sorry i have the aw4 automatic. I listened to the videos, and it does resemble it, but just not as loud as some of them. So if it is that, it must not be too bad and is just a crack. Is there a way to check? I do a lot of my own work, but i dont even know where i would find the flexplate. I just know its by the transmission somewhere lol

bigbadon

Is it in sync with engine or is it a fast rattle/knock? Check the harmonic balancer pulley after 15 years it may be loose.
Before you get into much of a panic start paying attention to other 4.0s when your next to one at a stoplight or in a parking lot. I have seen very few that did not make a little noise.
A rod knock will get louder and louder as you accelerate. Valve train noise (rocker lash, camshaft tingle) will usually go away above 2000rpm.

Ye Ol' Cherokee

Its deffinitely not in sync with the engine too much. Itl seem like it is, then it wont. Itd definitely not a uniform noise. Almost sounds like the clatter i had in my.old sebring but with more of a knock to it. Its sort of a random knock id say. Im really starting to.lean towards the flexplate, and im hoping that if it is, its only the bolts since its not too loud

jj1562

Look in the "write up" section, someone posted how to get to the bolts, it's a matter of taking off the inspection plate and getting your hand up there and checking the bolts and or for cracks, from what I hear, the cracks can be really thin so try to get a lite up there

Ye Ol' Cherokee

Yea i was actually reading that. Seems simple enough to do, but i know ill be proved wrong when i actually try it.. Probably wont get to it for a couple weeks. In the meantime, im going to try to figure out how to get these audio files posted so you guys can hear it yourselves

jj1562

And if you do end up doing that, please come back and share your info, 1 guy swears it's normal and the other thinks it's the bearings, but mine doesn't get louder with the Rpm's so with fingers crossed it's just the bolts being loose lol

cruiser54

Do this before getting off on any other tangents:


https://www.cherokeeforum.com/f51/ho...ocking-125547/

bigbadon

No need to put it off. It can be done in about 15 minutes. I done mine just for the heck of it.

DFlintstone

You can just make a U-Tube and post the link.... ( highly doubt mine is a Rod Btw.)

PocketsEmpty

If it's the flexplate, you'll hear it more towards the back of the engine. If you stick your noggin under there, you'll see a plate by where the exhaust bends down right behind the oil pan. That's the flexplate. It's easy to do. I had the same issue except mine was an awful rattling, most noticeable in Park or Neutral. It would stop when I put it in drive.

Definitely good security to remove the flexplate bolts one at a time and re-torque with red loctite.

cruiser54

Absolutely correct. Just do it.

BlueRidgeMark

Yep. Before you wish you had done it sooner.

Just consider it as preventive maintenance, like an oil change.