you.had.me.at.JEEP

Okay, for quite some time now my 4.0 has been tapping and it sounds dieselish. I've used my Haynes Repair manual and did some troubleshooting. I've ruled out worn piston pins or pin holes, worn or damaged connecting rod bearings, and abnormal piston and cylinder wear. The problem seems to be with the lifters, which I know is common with 4.0s, but I could be wrong.
The tapping becomes more rapid as the engine accelerates, and it doesn't fade away when the engine warms up. I don't have any loss of power either. I just performed an oil change, and I am now using Rotella T 15-40, and I added a quart of Lucas Oil Stabilizer; the dieslish noise is still present. A mechanic I trust (who also owns and drives a 4.0 Cherokee) recommended I run 20-50 instead.
Is there a product available specifically for quieting noisey lifters, or are there any simple fixes? As I stated previously, I don't have any power loss, or mechanical problems due to this noise; its just annoying!
Any recomendations are greatly appreciated! Thank you in advance.

94JeepCherokeeMan

New head. Lol, jk. I've considered it, though. Get a factory service manual and take the valvetrain apart. Replace the worn out parts.

you.had.me.at.JEEP

Aahhh! All I saw was, "new head"! I have a Haynes Repair manual for my '94 Cherokee and it provides step by step instructions on just about everything, based on a complete tear down and rebuild. I know there are other manuals out there, too. Which would you recommend?

94JeepCherokeeMan

Does it go through how to rebuild the head?

wiggles

I'd swear I heard that that was a hint of needing a new water pump. I would try that first before a rebuild.

94JeepCherokeeMan

I've stethoscoped mine, and the sound comes from the valve cover area. My water pump was replaced a few years ago, and it didn't make the noise before it went out.

you.had.me.at.JEEP

I replaced the water pump less that 12,000 miles ago, and the sound coming from the worn out pump was slightly different. However, I admit the possibility of a defective water pump is there. (I bought a refurbished pump from O'rielly's) Fortunately, it has a lifetime warranty! I'll check it out and see if it's the culprit! Thanks!
I'll get back on here tomorrow with a diagnoses of the pump!

I'll check the local Ace and get a good piece of rubber tubing. Hopefully I can locate the area if the water pump is ruled out and start cleaning some lifters and rocker arms!

94JeepCherokeeMan

Btw, I did some research on that lucas oil stabilizer, cuz I use it too. All it is is 80w gear oil. I shy away from that particular lucas product now. I suggest a high-quality synthetic oil, like Mobil 1 ($25/5 qts. at wally world) or Pennzoil Ultra. Hell, Valvoline MaxLife High Mileage. Stick with 10W-30 or 5W-30 (depending on temps where you are at). The higher viscosity stuff doesn't really help much, IMHO. A lot of people swear by MMO, but I think that's just tranny fluid. Might help tho, i'll have to try it.

94JeepCherokeeMan

Hollow metal or plastic broom handles work great as a stethoscope, as well as those siphon tubes for fish tanks lol

sycoglitch

Well I've had my pump go on me last year and for a few months I had a diesel engine cause of it. OP, take your belt off and jiggle the gears

94JeepCherokeeMan

Lol my engine has sounded dieselish for over a year now.

Jeepability

shaeffers oil is probably the best oil out there. it beats any oil any day even royal purple. http://www.schaefferoil.com/

Moncheche

I just replaced my lifters. Dieselish sound is 90% better. (these 4.0L always sound a bit like a diesel)
I had just replaced the head due to a crack (0331 head, another story) and i had fired up the engine after torquing the cap screws. I had little to no lubrication. I pulled the head and took a look at my lifters. 5 were junk junk and the other 7 were marginal. The new ones went in fast and now I have oil pumping like crazy. You will hear about how 'bad' it is to replace lifters without replacing the cam, but I've never had problems doing that. Check my top end lubrication thread. https://www.cherokeeforum.com/f2/roc...uestion-96005/

Additionally, I don't agree with the heavy weight oil. It just doesn't make sense. Check out this website. Lengthy but very good info. http://www.bobistheoilguy.com/

Good luck.

you.had.me.at.JEEP

So I've noticed something new today. The dieselish noise doesn't happen right after I start my Jeep, it occurs roughly 30-45 seconds after the engine is running. I did use a quart of Lucas when I changed my oil recently. After reading your posts regarding Lucas I, too, did a little research and found the same thing; it consists of 80w gear oil and Zinc additives. The zinc may help with breaking down the gunk and build up, and coating the internal parts, but I can't help feeling that such a thick gear oil is any benefit to the motor.

Needless to say, I won't be using Lucas any longer! As far as using the heavier oil, several 4.0 owners have experienced longer lasting engines and less oil consumption with 15w-40 and higher blends. My 4.0 does seem to run smoother, and power seems to have been restored after my recent oil changed, compared to how it was prior. (I was running full synthetic10w-30 and a quart of Lucas) Makes me wonder though.... If I'm experiencing a slight, yet noticable restoration of power and smoother engine operations with the heavier oil AND I added a quart of Lucas; how would it be had I left the Lucas Oil Fouler out?

Another update! I just spoke with someone about the noise and he had an interesting point. If there is an exhaust leak at the head near the block, a rapid tap, tap, tap noise (that annoying dieselish sound) will occur. Hmm... I figure it's worth the effort to check it out!

If an exhaust leak turns out to be the culprit, what harm is there in letting my Jeep continue its fantasy of having a diesel?

djb383

Most leaks, of whatever nature, usually just get worse with time/miles. It takes more power to pump heavier oil.....that power went from the wheels to the oil pump.