centuryhouse

I just picked up an XJ fairly cheap. I didn't notice this on the test drive but it was windy and loud so I may have missed it.

Background: The engine reads 236k miles. There is a receipt for a complete rebuilt at 113k. And the person I bought it from says he refreshed (rebuilt) the heads 50k miles ago not because there was a problem but because he didn't know what had been done to it and wanted to do it himself.

I took it a few hundred miles today and noticed a diesel sounding clattering at times. At RPMs between 1500-1700, it made this noise sometimes - but at other times at the same rpm it didn't. It made the noise more around 25-55 mph but it seems to completely go away once I'm up at 60mph or over, even though the RPMs are the same.

This is a standard transmission and I'm used to the automatic transmission on my other XJ. Could it be rattling from the manual transmission? Or if the engine, what is likely to cause that?

Larry's XJ

How's the oil level? Could change it if you don't know when last done. How's oil pressure??

investinwaffles

I usually only have the diesel clatter sound in 1st gear at lower speeds, especially when taking off at a light (it is a fairly low compression inline 6, flat tappet style cam so not out of the ordinary). I like the diesel clatter sound, which is probably why I sometimes like to pretend that the diesel truck next to me on the highway is actually my XJ's engine

I would also ask the question of what and how much oil. If you are in Texas, I would really recommend using 5.5qt of Rotella T 15w-40 and .5qt of Marvel Mystery Oil. Really makes my higher mileage 4.0 sound smooth like a sewing machine.

Although I am pretty sure my noise is coming from the lifters or valvetrain, which should be new-ish in your motor??

RED RIVER

Mine has a diesel sound to it only at idle above 800 rpm it goes away. It's been like that for years, every one that has heard it just shrugs. I'm thinking its lifter sound.

jaydubz

4.0L are basically diesel tractor engines. =0

investinwaffles

calling all salads, lol

He hates when people call the 4.0 a "tractor" engine

JeremyXJ

My 4.0 auto sounds like a diesel at idle. Lots of chatter. Even after a fresh fill of 10w30 full synthetic. It quiets down once I start moving. I think it's pretty normal.

centuryhouse

If it is supposed to make that sound then I'm good with it. Just getting used to this new XJ and it sounds different than my 2000, so I got nervous.

I think it may be resolved now. There is still a little of that deisel sound but no more than my other Jeep. I'll drive it more today to make sure.

I think the culprit was the AX15 (?) manual transmission. The former owner used all AMSOIL fluids, including for the transmission. I read that some people got a clattering with Amsoil.

So I bought 4 quarts of REDLINE MT-90 and drained/filled the trans.

The Amsoil was super clean coming out, but sure enough 80% of the clattering sound I was hearing seems to be gone now that I have Redline in it. It seems to shift a little smoother now too.

I also changed the oil and put on a NAPA Gold filter, which seemed to have made a little impact as well.

RED RIVER

I wouldn't say it's "supposed" to sound that way but it' is "abnormally normal" with the 4.0 after a lot of miles. It's definitely a wear issue of some sort but if it's running smooth I wouldn't worry about it.