Just bought an 00 XJ 4.0L 2wd with a knock. since the day i first saw it, i was sure it was the flexplate, tomorrow a local mechanical will be changing it for $300. i began to watch other videos and read other posts and people said it could be piston slap, rod knock, rod bearings, etc and I am very scared that the flexplate might not be it. The knock is audible from startup but as it warms up and after a 30min drive, it sounds VERY bad, which is why now im doubting its the flexplate because would heat cause it to get louder??

Im a VERY BUSY 19 year old college student with little money, please help! if the mechanic replaces the flexplate and it doesnt fix the knock, where should i go from here??

 

i would crawl around under it with it running and listen to where the knock is coming from.

 

There is a very detailed write up and video of the noise on here about the flex plate bolts being loose, check it out and see if it's the same sound

 

i know my flex plate bolts arent loose, i believe the flex plate is cracked, my 89 XJ has loose flex plate bolts so i know what it sounds like. i hope so much that its a cracked flex plate

 

mine was louder when it was warm. did you pull the torque converter cover off and look up there to see if it was cracked? you have to look real close.

 

the "inspection cover" thing, yeah i did but it was dark and i couldnt see much, the crack really occurs on the center bolts so it cant be seen from the there. but im so glad to hear that!

 

Gotta remember heat expands thing which can cause cracks to get bigger causing louder noises...

 

when mine was cracked it sounded like this.

 

If it's badly cracked it will sound like this.

 

I thought I saved it but now can't find it. crap!!

 

I hope it is the flexplate and yeah i knew heat affected metal like that, im just so scared, if its not the flexplate, my future is on the line! lol thank you all for the help

 

I FOUND IT!

https://www.cherokeeforum.com/f2/fou...emoval-171945/

 

TY cruiser!

 

And I saved it real good tis time. Right below the write-up for checking and tightening flexplate bolts!!

 

i left it at the mechanics and after work i go to pick it up, and they didnt do anything. they said they removed the inspection cover, saw no cracks, so they charged me $80 and told me it was a rod knock. i was SUPER mad and drove home like crazy accelerating like crazy and popped the hood open and realized they might be right. the knock sounds like its coming from mid engine, but the engine runs so well!