xjmercenary90

Hey guys I just did another oil change o switched to valvoline high miles synthetic blend with a wix filter my engine now sounds like a diesel someone told me I might need new main bearings. Is tgat tge case? If so can it be done without pulling engine? Any advice would be great. 1990 cherokee 4.0 renix with 240k also she's seems to be getting gutless on freeway what could be causing loss of power??
Ty in advance

salad

Sooo it started making noise after you changed the oil?

Did you put the drain plug back?

xjmercenary90

Lol yeah drain plug is in I've got good pressure etc. It didn't start right after change per say it just got louder

xjmercenary90

And why am I listed as newbie?? I've paid my subscription again grrrr

colt44

My XJ has sounded like a diesel for 19 years! If it got louder after an oil change, see Salads's answer, or better yet, look at your oil pressure gauge. It should have about 20-30psi at idle, and 40-50 at driving rpm's. Maybe you're just paying more attention to noise because you just changed oil? If you're running a good oil pressure, you should be fine. One thing I've learned about 4.0's is that at higher mileages, [above 150,000] they like thicker oil. Salad had a great oil thread a while ago about using 15x-40 Rotella and it helped me quiet my XJ down a little. But they still make noise.....

xjmercenary90

I was wondering about that. It did get louder after switching to the synthetic blend. I'm using the 10-30 blend for high mileage engines. I've heard once you go synthetic your stuck with it. Is tgat the same for the blend? Or should I go thicker oil next time?

colt44

No, that's not true. You can switch back and forth between synthetic and convential with no problem. As a matter of fact, most oil companies also sell 'blends' of synthetic and convential at a slighty reduced price than full synthetic. Look at 'Salads' thread on this forum about engine oil for 4.0's. He's not paying me to say this, but it's one of the most comprehensive review of engine oils I've ever seen. I used his advice on Rotella, and I was happy w/results. Old 4.0's like thicker oil.

salad

lol you have to go and set your title to whatever you want it to be :P

What oil was in it before? Some engines do better or worse on some kinds. If I observed a change like that I'd just go back to whatever you were running before assuming it wasn't molasses.

For fun, have you eliminated the flexplate bolts as a source of noise?

jeepkid03

Try going back to whatever oil you ran before and see if that helps. I've noticed my 4.0 is a bit more noisy than normal when running a synthetic oil compared to a conventional. It doesn't hurt anything, but theres definitely a difference.

cruiser54

Yeah. Flexplate bolts should be eliminated as a possible cause, or a cracked flexplate. See the links below.

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

Straightshooterjeeps cracked flexplate diagnosis

I removed 3 of the 4 bolts.

Then loosened the last bolt about half way.... I left this one in to maintain connection between the tq and the plate. Just so I wouln't have to fiddle with putting bolts back in too much.

Now the flexplate is pretty much seperate from the torque converter.

Got my flashlight pointed up in there

Grabbed a big flathead screwdriver and started prying on the flexplate

Don't see anything yet

Turn the flexplate a half rotation

Pry again

and there it is! A big fat crack up near the center of the plate.

When the flexplate is loose from the torque converter you can get it to "flex" real good and you just might be able to spot your crack.

Just to be sure you do have one before dissasembly.

It was very obvious at this point, but before pulling those bolts I looked and looked and could never see a crack.

Hope this helps save someone a little time.

CCKen

With a high time engine like yours the camshaft is probably corn cobbed.

xjmercenary90

What is this corn cob of which you speak?? Damnit now I want corn

kgm

I used Castrol himile and my engine sounded loud as hell. It was like Click & Clack were right in there, just banging around!

CCKen

You know....what you use when you run out of toilet paper.

Kalali

Ouch, that really hurts...