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Jeep Cherokee Forum (https://www.cherokeeforum.com/)
-   Stock XJ Cherokee Tech. All XJ Non-modified/stock questions go here (https://www.cherokeeforum.com/f2/)
-   -   Top end knock (https://www.cherokeeforum.com/f2/top-end-knock-46000/)

sexy_hotfootball_stud00 04-29-2010 09:17 AM
Originally Posted by tannerp89 (Post 521356)
x2....pull the rods and lifters and inspect both, that sounds like a collapsed lifter (loud ticking when cold/at idle is because of low oil pressure and ticking while hot is due to low oil viscosity) meaning your not moving enough oil through the lifter.
its not just at idle either. it randomly knocks and then just stops randomly. at first it wasn't very often. now it does it every time i drive it.

tannerp89 04-29-2010 10:27 AM
Originally Posted by 98 JeepJeep (Post 522067)
nope...not on a HO 4.0....Head has to come off.......
ummm no. i did this a 2 months ago when i tore my donor block apart.

sexy_hotfootball_stud00 04-30-2010 10:54 AM
Originally Posted by tannerp89 (Post 521327)
collapsed lifter, or a bent pushrod, or bent valve. most likely a collapsed lifter. did you pull the rods when you replaced the rocker pivots/bridges. also rocker pivots have a short break in time where they will make a slight tick until they seat...
anyway i don't think it'd be a lifter or valve bc wouldn't it run like crap? it runs great no problems other than the knock.

ColoradoJeepXJ 04-30-2010 11:04 AM
I just went through this. The engine would run fine, just a loud knock that would come and go. It sounded like top end noise, lifter or pushrod problem but it turned out to be piston slap. Replaced 3 pistons, all rings and rod bearings and it runs great. Total cost about $250 in parts, the pistons came from the JY @ $5 ea.

My375hp302 04-30-2010 11:51 AM
Originally Posted by sexy_hotfootball_stud00 (Post 523726)
anyway i don't think it'd be a lifter or valve bc wouldn't it run like crap? it runs great no problems other than the knock.
Sounds like your in the same boat as me. I was pretty sure it was valvetrain noise but I check all of the lifters, pushrods, and rockers and the noise is not coming from them. It's lower in the block. We are both driving on borrowed time. Start saving for a new shortblock and in the meantime run SAE 30 motor oil and one quart of Lucas oil stabilizer. That should thicken the oil up and cushin whatever is knocking. Might make it last a tad longer.

tannerp89 04-30-2010 02:26 PM
ya hes right on that....if youve eliminated every thing from the top end it has to be piston slap....and it wouldnt necesarily run like ****, but wouldnt have the power it used to due to the valve not opening fully...

sexy_hotfootball_stud00 04-30-2010 08:42 PM
the bottom end is a jasper rebuild with less than 50K on it and the top end has 85K. i know its not coming from the bottom end.

sexy_hotfootball_stud00 04-30-2010 08:43 PM
'

sexy_hotfootball_stud00 05-08-2010 01:55 PM
replaced the pushrods and still no luck.

ColoradoJeepXJ 05-10-2010 09:38 AM
I still think it's the lower end.

McRay 05-10-2010 11:05 AM
might try a heavier oil and checking transmission flex plate if its auto-transmission - be my guest its in the lower unit like low sound rod knock. I just change 4.0 for the same sound. Hope you located the problem

sexy_hotfootball_stud00 05-11-2010 09:45 AM
so the pushrods did fix it.. they kocked at first but been driving it around for a while and no knocks.

ironmoto524 05-24-2010 11:19 AM
it goes like this....you must pull the head to access the lifters they are to large in diameter to fit through the push rods guide hole. good news is that lifters gaskets and everything i replaced before did the trick!took 8-9 hrs but time well spent if you hate a knock noise!:gun_bandana:take no prisoners


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