Dogface

Newbee to this forum but not to the wheeling world. Just picked up a 96 cherokee and sounds like it has a faint knock, you have to really listen for it but its more defined when going through a drive thru.

I`ve heard that the 4.0 can have a noisy valve train but its hard to say.
The knock seems to come and go not really getting any louder.

Question is, can the oil pan be dropped without pulling the motor?

Is the 4.0 known for bearing noise and or failier, It only has 131.000
But I think it was not maintained like it should have. Maybe its new motor time, anyone have a good motor in MN they want to part with.

Thanks

ZachsXJ

I haven't done it yet but I'm pretty sure you can drop the pan with the motor in the Jeep

bigomudders

Take flywheel inspection cover off and look for a spider web cracks around flywheel these XJ's are bad about it.

UserID6095

You can drop the pan with the engine in but on stock height it can be a tight fit.

Does it get louder with as rpm increases?

Sounds more like valve train. Run it till she blows, who knows you might get 300k out of it with the "knock."

Dogface

You guys are quick, I will check the flywheel good idea, I had an old buick that had a cracked flywheel and it knocked.

It kind of goes away when you rev it but still doesnt seem right. And your right I should just run it till she blows but it would happen on the coldest day -20 or so and leave me stranded thats my luck.

I did look at it and it appears that I would need to drop the front axle down slightly to obtain easier access.

Thanks

winston427

If you find cracks in the flexplate then you will most likely find even worse when you remove it to replace it. Mine started with a slight tick and developed into a loud knock. When I pulled the trans to replace the flexplate I found that it was completlye broke around the bolts that hold it to the crank.

UserID6095

If it goes away, lets say above 1500rpm, then IMO thats valve train issue. Atleast mine was.

You can try a Seafoam treatment and Oil with a high ZDDP content. That should help.

winston427

Mine had the knock at idle and would go away when under acceleration. The engine torque would keep pressure on the broken part and prevent the knock. At idle it would have enough play to drive you up the wall. Anyone near me at a red light would stare in disbelief waiting for it to blow up.

ironmoto524

im hurting in the same way!! my 88 xj has a slight knock at idle that seems to go away at about 2500 to 3000 rpm. compression test was 132 in the #1 spot and 140 in the other five!oil pressure around half(40 by my gauge)!no loss of power just a ugly sound

owellwhatever

Could be piston slap. It's very common. The 93 I had had piston slap, sounded like a dull knock and you couldn't hear it unless at idle. Drove it that way for 100k

ironmoto524

well i pulled the valve cover off and found that my 1 , 3 , and 5 spots all have play in the pushrods and rocker arms....curious if i was to replace the pivots, rocker arms,bridges, and rods would that be ok?? i have only driven maybe 50 miles since onset of noise! or should i be pulling the head and going deeper?? any advice?

ZachsXJ

has anyone considering timing chain slap? it sounds horrible when it gets bad, my buddy had it so bad on his TJ we swore up and down he had rod knock, turned out his timing chain was super loose. mine is so bad I thought it was my lifters till a friend of mine told me otherwise.

Matteo_96xj

Just to add one more thing to look at, my PS pump went bad and it sounded EXACTLY like a bottom end knock. Couldn't tell it wasn't until we put a stethoscope on it. My valvetrain is a bit noisy too, I'm not going to worry about it until it gets worse.

ironmoto524

oh well!!i just put new rods rocker arms pivots and bridges in and torqued to 19 ft#. still taps best i can figure is worn lifter(when you remove #5 plug wire tapping noise goes away and reappears as soon as wire is reconected)!!when she warms up i can barely hear noise but now my belt wants to squeal!jeep just wants to be loud i suppose!thanks for all your input!!

Matteo_96xj

My belt has to be really tight not to squeal, if you can move it more than about an 1/8", try to tighten it a bit more.

On another note, anyone here change lifters on a 4.0? Do you have to pull the head?