Hey just got my cherokee its the 4.0 with a manual 5 speed 1999. jeep was fine when I got it but now it making a small knocking noise which sounds exactly like a worn piston rod bearing. I have had a 4runner before and have had the piston rod bearings go on me twice screwing up two engines. So now I am super careful. I pulled the oil pan today to see if there would be any play with the pistons on the crank and it seemed nice and tight!
now could the noise come from some parts linked to the camshaft lol just discovered it was in the lower part of the engine sorry i am a newb with the inline 6 4.0. So any sugestion will be good and i am also looking for a technical manual for all the torque specification ! thanks for the help if i figure it out I will post a ful repair guide wih pictures of the problem I had thanks guys.

 

Check your engine oil or the oil pan for metal filings (copper). Anything you can see with your naked eye is bad. If that's the case, you may still be able to save it, but you need to check the crank journals for marring, scratches, etc. Anything that catches your fingernail needs to be machined off, or your new bearings won't last a week. I haven't replaced rod bearings on a Jeep yet, but, generally, if you can take the oil pan off without putting the engine on a hoist, you should be able to replace them within 5 to 6 hours. Please, watch the torque specs and procedures on tightening the rod bolts (it's usually a 2-stage process), to make sure, that a) none of them comes loose and b) none of them breaks. Each case will cost you a replacement engine.

 

could be a bunch of carbon, mine had a spark knock till I put the stock t-stat back in "never had a engine love 210 so much" sounded like a rod knock. Do you have hard starting?

 

Is the noise constant or is it only apparent at start up and revving the motor? If it isn't constant, I would check the torque converter bolts to make sure they are nice and tight.

 

hey not to thread jack here at all but im brand new here and my jeep is doing exactly what you described with the knocking on start up and reving the motor. i just bought it and it started doing this. do you know what it could be? thx again hoping im not thread jacking

 

mj6886 pm sent.

 

Haha nice no your not tread jacking at all. I am just trying to figure this problem out too.

 

What do you mean by bunch of carbon where would I need to chek for that carbon. No starting problems. Basically i start it up and it fine and after lets say 45 sec i can ear that noise comming from the bottom of the engine.

 

Chech this first

 

X2 on this one...also see if the Flywheel is cracked by the bolts...Tj

 

So I did not see anything in the oil pan no metal flakes nothing it was pretty clean actually so good news...only the usual deposits. SO im thinking I will take the rest apart to inspect the crank journals and check the bearings for wear and such. if its in good shape i will replace all of them anyways it will be done and won't have to worry about it for a while. but since the camshaft is in the bottom part of the engine that noise may have comme from there too so what am I supose to do to check that if it turns out it wasnt a rod bearing knock ?

Other questions... do you guys recomend using OEM stuff for the bearings of aftermarket is fine ? and if you guys have any other work or inspection i should do while the oil pan is off let me know.

 

Its definitely not torque converter since its a manual. Flywheel cracked by the bolts really ? the noise is really comming from inside than pan I mean i stuck my hear on it and it was clear it was right in there. Have you had problems with the flywheel before ?

 

it really can be a piston slap due to inconsistent combustion. try plugs and wires and rotor, and a high voltage coil. unless you have the dist. less system my 2000 tj did not sure on cherokee's.

 

Yeah disregard on the torque converter, guess I over read that part. Check the flywheel.

 

Hi don't know if this helps but my 88 has a really bad knocking at idle ,and after you rev it up and let off,but it is an inconsistent noise some times really loud other times not there. I had the pan and the timing cover off to see if I could find anything.everything looked really good. I suspect that its the oil pump bypass its located right under the distributor,even though I have good oil pressure I want to replace the pump to see if that helps. I figure I'll do it when I do the rear main seal,when that day comes ill post if it takes care of it .