Take pics lol

 

If he flex plate bolts and bolt hloes are good, and there's no cracks in the flex plate, try this:

1. Remove the serpentine belt and run the engine to isolate any belt driven components.

2. Get a mechanic's stethoscope from the auto parts store ($10), or use a wood dowl of suitable length held to your ear, and see if you can listen at the timing chain cover (BE CAREFUL), and listen at the base of the distributor on the engine block.

3. Remove the distributor cap and see if the rotor shaft has any play in all directions.

Note that up to, and including 1998, the 4.0 had a spring and a pin on the front end of the camshaft to put an aft preload on cam. These spring/pin setups have been known to fail and cause a knocking sound, heard in the timing chain cover area. Cam walking is the term used for this. Cam walking may also cause oil pressure fluxuation as the cam walks fore and aft over the cam bearings, covering and uncovering the oil passages in the cam bearings.

Starting in '99 the sping/pin was replaced by a thrust plate.

 

Also check the crankshaft vibration damper for it hiting the timing chain cover. These dampers have a habit of coming apart.

 

Flex plate bolts are good. Can't really check for cracks due to the fly wheel being in the way. I think I isolated the noise to the front of the motor and it seems like it coming from the water pump or right behind the pump, I put the stethoscope on the top of the pump and the hose coming out. Most of the noise is found here or right behind the pump.
Question, can I remove the belt and run it for less than a minute to listen for the noise to rule out the pump?

 

I guess my phone didn't update the new post before I wrote my last one. Thanks for the advice. I am trying that now. Also y'all are calling the plate bolted to the fly wheel the flex plate right, not the fly wheel. I can only see the outside rim of the plate behind the fly wheel

 

Thanks for the advice. I am checking all those things in order. I did have a flex plate bolt loose but maybe got a quarter turn on it. I am taking off the belt now and will let you know what I find. If I get to the point of checking the dampner, where is it? I know where the timing chain is but I would like to know exactly where. Thanks

 

The damper is the large 'pulley' at the bottom of the timing chain cover that drives the serpetine belt. Crawl under the front of the Jeep and you can get a good look at it.

 

That is the flexplate in the pic. It is bolted to the crankshaft and the four bolts you checked hold the torque converter to the flexplate. Chrysler calls it a Drive Plate.

 

I gotcha. I grew up calling that a fly wheel. Well I just removed the belt and started it up. No noise!!! I took video again today of the belt installed with the noise and the belt removed with no noise and uploaded it to YouTube. I will post the link as soon as they finish uploading. I am personally suspecting the water pump going bad, let me know what you think?

 

This first is with the belt installed



Next is with it removed


I know there is still noise that a brand new engine would not make but it's normal for this engine. The troubling noise in the first video is gone

 

When my 95 was knocking like that it ended up being the water pump one time and the idler pulley the next time. Took the belt off and it went away just like yours did.

 

I guess you know what to do next...H2O pump. Good find. Don't get a crappy pump from Autozone, go with an OEM pump from the dealer or top of the line from NAPA. I think the heater hose tube can be obtained from NAPA as well (I haven't checked - I got mine from the dealer).

A few extra bux will be worthwhile if you change the tensioner pully as well. Examine the belt closely for cracks.

Better than unarsing the bottom of your motor isn't it.

 

As an Aircraft Mechanic you know not to leave any stone unturned.

While the drive belt is off, check the alternator bearings by slowly turning the pulley and see if you can feel any defects. Check the mechanical fan bearing same way. If you're not going to change the tensioner pulley check it as well. Also don't forget to inspect the vibation damper.

CCKen
USAF Aircraft Mechanic
Feb 64-Feb 68 (VN Class of 67)
Civilian Aircraft Mechanic
Feb 68-Feb 07
Retired Aircraft Mechanic
Feb 07-Feb 13

 

Oh yeah I will check everything, and yes way better than taking the motor apart. I hope this thread helps others with this problem

Always good to talk to another aircraft mechanic, I worked A-10's from 01-05 then A-10's, F-15's, F-16's and a little on Huey's from 05 - 2011 in a test squadron. Now I have been on C-130J's since 2011

 

Listen to the difference