OK my truck has what seems to be a loud knock when idle bellow 1000 rpms, one it gets past 1000 rpms its fine. ive had plenty of motors that started knocking, but this is inconsistent knock. Now say im in 1st gear and i go to 4500 rpms and let off i get a strange rattle noise till 3000 rpm then it goes away. I am stumped. 4.0L 255.xxx miles

has oil, the gauge never really goes past 30 and gets pretty low at idle.

 

Tried this? https://www.cherokeeforum.com/f51/ho...ocking-125547/

 

What brand oil filter are you using?

 

If it's coming from the middle of the engine, it could be wristpins or rod bearings.

If it's a deeper knock down low, it could be the main bearings.

Oil pressure is a little low. When bearing clearances get wide, the pressure is going to drop.

 

I would definitely check this before you jump to any conclusions.. Buddy had a cherokee that sounded just like it was knocking, turned out to be this.

 

My most recent (now sold) '89 had a very similar problem. Wasn't the flex plate though. Just cause I'm curious I'll keep my eye on this thread lol. Sorry I couldn't help. Good luck!

 

flex plate bolts?

 

water pump? take your belt off and run it....if the sound stops its something belt driven...in my case it was my water pump

 

I just cured a knocking by changing the bushes on the transfer case linkage. It never really sounded like an engine knock, more of a dashboard rattle, but it was loud and metal to metal at times. You can tell if it is this by just moving the transfer case lever up a little and see if the knock goes away.

 

thanks everyone ill check the flex plate bolts, and the oil filter is a purolator the knock is coming from the back of the motor could be trans, that would make sense.

 

yup they are lose, and i just changed the water pump.

 

I'm glad it was a cheap fix this time.