Hello,


Well I bought my first 1999 Jeep Cherokee about 2 months ago. I have been driving it daily with no problems and no noises that I was aware of, except for the normal piston slap. I was driving down the road a week ago and started hearing a bad clattering. It sounded like a rocker assembly had broken and they were just clattering really bad. When I push on the gas the clattering gets louder and does not seem to go away. If I hold the gas at a decent RPM The sound kind of evens out and I can hear the engine misfiring. So I drove it home then to my mechanic. He took off the valve cover and all the rocker assemblys are fine. So the sound is more internal. He said that it sounds like it is coming from the upper end though.

I am writing to see if anyone else has experienced this?
If so what is it?
Does anyone have any ideas?
Is there a common problem that causes this?

Thanks

 

Possible bad lifter or valve? Did he check any of the valve springs?

 

Shot in the dark, but take off your serp belt and check all your pulleys for play. I've done the water pump on two Cherokees now where the pulley bearing went bad and it sounded like a grumbling sort of valve tap.

 

mine did the same noise. collasped lift on #6. i couldnt go faster than 45



that moved .25" atleast

 

He had it hooked up to a trigger that turned the engine last time I was there. The trigger turned the engine over when he pulled it so you could see the the rockers move. They all moved the same amount. He also noticed that when he clicked the trigger a few times you could not hear the noise till the serpentine belt system traveled backward. Thats when you heard the tap. When he pulled the trigger and the belts traveled the correct way you heared nothing but when it spun back there was the tap.

 

Seen a few make the same noise and turned out to be loose flywheel bolts...just a suggestion

 

Any other suggestions? I want to give him a few things to look at tomarrow.

 

broken piston skirt?

 

I had a broken piston skirt in my 96. Not saying that that is what you've got, but if you will look on youtube(search jeep 4.0 engine noise) you can pretty much pinpoint the noise upon comparison. The posts run thru loose flywheel bolts, spun bearings, dropped valves,broken rods, piston skirts etc. Hope that helps. My Jeep ran fine even with a broken piston, goos oil pressure n all! Just sounded bad and worsened upon acceleration. Good luck hope its nothing serious!

 

is that your profile pic?

 

Yup that's the number 6 piston! I think it must have gotten overreved.

 

So I went to youtube and listened to the engine noises and based on the sounds that I was hearing, I suggested that my mechanic tear off the oil pan and look at the pistons. Low and behold a broken piston, fantastic. I just bought the damn thing. Looks like that was why the guy I bought it from told me he changed the valve cover and the oil pan gasket, what a dick.

All I can say is if your 4.0 starts clacking like a bad lifter pull the valve cover, check the rods and rockers. If that turns out to not be problem, then pull the oil pan and check for metal.

Seems that this is a common problem among 4.0 engines. Now I need a new one.

 

Hate that for you. I was in the same boat. When i bought my '96 i just thought i had a bad exhaust manifold. It had cracked and been welded. The engine was making a "ticking" noise but it ran great and had good oil pressure. Pulled the dipstick the oil looked good. No problem i said! Easy fix! I drove it two days n all hell broke loose! The "ticking" got REAL bad! That was 4 months ago- still workin on the rebuild. Its gettin a lil expensive! I may suggest a junkyard motor if you need a quick replacement. I wanted to rebuild mine with new parts because i plan on taking long trips with my XJ.

 

how many miles on yours?

 

155,xxx