Ye Ol' Cherokee

Okay so, i had an ongoing post going about my knock in my 98 4.0, (Thanks everyone for all your help on that) .. anyway, i thoroughly inspected the flex plate and locktited and torqued the bolts to spec, and still have the same knock.

Its definitely not a bad knock as it is not loud at all. Its really not bad, but it is there.

I'm pretty sure i have it narrowed down to a rod, but that's well beyond my skill, so while i am working that out, i want to know what to do with my oil, so here we go.

I bought the truck, put in 10w30 Castrol High Mileage syn blend, and like the old lady in the frank's hot sauce commercial says, "I put that sh** in everything". And since then, i have been using this oil.

I have a light rod knock i believe, and im not sure if it was there before i changed the oil because i changed the oil on my second day of ownership

ANYWAY... should i switch to Rotella T 15w40 like EVERYONE is saying to do? I have heard so many good things about it in the jeep 4.0, but i have also heard sob stories about it causing failed headgaskets and seized engines (Essentially because it is not spec. oil).

I don't want to just throw it in there to make the knock go away if its going to make things worse because it is thicker. But then, if it will actually benefit the engine in the condition that its in, well then hey, i'm jumping on the band wagon !

The engine runs well, has no lost power, and has been verified with a mechanical gauge that it runs right on the money @ 13 psi when at its hottest idle.

P.S. i live in philadelphia, Pa where the winters are COLD (as low as 10 degrees sometimes) and the summers are HOT (High 90's on some days), so any reccomendations based on that info would be appreciated.

Thanks for the help guys

JLW_2K13

A parts tore recommended to me that I should run 5w 30. After I put it in I was getting a knock. I changed it back to 10w30 and It went away.

95Cherokee

Does it sound like this? Go to minute 17:22 in the vid.

salad

Rotella's great, I wouldn't recommend 15w40 for cold winters. T5 and T6 come in much better startup viscosities like 0W40 and 5W40. There're also a 0W30 and 10W30.

As for causing head gasket failures for being out of spec, that's a load of crap. The 4.0L was originally specified with 15W40 and 10W40 is still used in Europe and Australia. It's fine for use, but obviously is thicker so cold weather performance is a real concern, and there is an impact on fuel economy. That said multigrade 40 synthetics have the best used oil analyses in these engines.

If you'd rather try swapping oils than a rebuild or finding where the noise is really coming from, go for it... try a few, see what the Jeep likes. The guy up there who changed from 5w30 to 10w30 probably switched brands or there was some other factor at play.

Don't forget to use a quality filter, cheap ones can cause these issues on their own. WIX 51452 is a pretty decent unit. (Similar to the 51515 but a lot more rugged... 51515 is really a 'car' filter and not built for much abuse like a Jeep should see). Knock the first 5 off for a NAPA Gold part number.

Love that video.

skife

"car" filter?
I've never ever heard of being separate car or truck versions of filters (besides size)

after saying that I'll run a motorcraft FL1-A (ford 5.0) or a purelator Pure one (same filter, different can) with a quality oil in 10w30 or bigger, ford dealer changed it with 5w20 syn blend and i don't like the oil pressure at warm idle.

cropduster

I have a knock too in my 01. It has been there unchanged for the 30K miles I have owned the XJ. I tried Delo 15-40 over the summer. It sounded louder when I ran that oil. I switched back to 10-30 high mileage and there are times when I do not hear it at all. The 4.0 likes 10-30 and a Purolator filter.

jj1562

I recently had the same issue, I was told it could possibly be a lifter tick and don't worry about to the point where I'm pulling my hair out, mine started after using rotella T-5, 2 oil changes ago, I'm going to try mobile 1 next,

salad

Yep. WIX builds filters in an application-oriented manner, the 51515 is essentially for automotive-only use. The 51452 is much more ruggedly constructed and is specified in heavy duty applications. If you drive your Jeep like a Jeep you stand a much lower chance of the 51452 failing due to collapsed media or some adhesive coming apart due to vibration and shock.

...why is 5w20 in an engine that was built for 30s and 40s?

Millie Smith

my vehicle does sound exactly like this what is it caused by?