acermcgraw

My last few threads have been about my struggle to locate a noise that sounds like metal on plastic, and that occurs in unison with the motors rotation. It is bad when the truck is cold, a little better when hot and at some times, nonexistent (the truck would seem to be magically repaired).

I have of course asked the oh so gracious an knowledgeable members and amins on the very site, for any advice they may have to offer. I have taken all of it and then some, doing even more research on my own.

Of course the first hing i checked was my flex plate. After about a half an hour of spinning it and checking it with my wrench and my flashlight i was unable to find a loosened bolt or a crack anywhere. I was then told to check the harmonic balancer, which i did and found that part of its rubber middle piece had begun to fall out (ah ha i thought) this must be the culprit. I promptly went down and bought a new one and was shocked to find out just how hard of a job that is. Once it was in i fired up the Jeep just to hear that same old familiar noise.

So here i sit wondering if this is just the most oddly sounding rod knock i have ever heard, or have i missed something. As these are the only two ideas that are predominantly used to diagnose this noise, i am in search of an alternate diagnosis.

Please if you have any ideas , i am willing to do almost anything to keep this jeep going , i have always wanted one, i finally got divorced and was finally "allowed" to get one. I really don't want to id of it but i can only have one car.

Oh and one more thing, the noise is definitely coming from the lower rear of the motor, between the bell housing and the rear of the engine. Feel free to ask anything to help in your diagnosis.

Thanksall

prerunner1982

Check your fan blades and see if they are rubbing against the fan shroud. If it is most likely the shroud has some broken mounts allowing it to move, or your motor mounts are toast allowing the engine to move.

BowtieGuy3

You sure it's not an exhaust leak or a lifter ticking?

acermcgraw

wow so quick thanks guys, The lifter is way to far away from the noise, it is much louder than a fan clicking and I have checked that too. The exhaust leak has been checked as well, but good ideas.

as far as the motor mounts, that's interesting becasue the motor does vibrate a little, it mellowed out when i replaced the harmonic balancer , but it isn't violent, plus im not sure that would explain why it is way worse first thing in the morning and sometimes non existent.

Those are some great ideas , please keep them coming, Thanks so much

XJ Stryker

Doesn't explain why it doesn't do it when its hot.

This is a good one. FIrst time looking at this post I will kick it around a lil and stare at my engine running and see if I can come up with anything.

If we can't help ya try www.NAXJA.org. they have alot of tech

JayM

Hey you have a recorder on your MP3 player?

record a minute of the sound for us, or use someones video camera and record it for us. Most digital cameras can record now a days.

One's of your firend's should have a camera with this ability.

Other wise we are just gussing, and sending you on wild goose chases.

XJ Stryker

I do like the motor mounts idea, cause it can cuase your motor to hit the fan shroud on and off. And bad mounts will cause a lot of vibes. I replaced mine on both jeeps right when I got them. I put a write up on here if you are unsure how to do them just look through the xj write ups

mike37

water pump is bad loosen the belt and jiggle the fan to see if the shaft moves around

acermcgraw

i will check the water pump but i really am pretty sure the noise is coming from the rear of the motor.

mike37

in the mooring its cold and has less water flow
as you drive it gets hotter and more waters will floe that helps dampen the noise and even stop it all together
your fan my not be connected to the water pump so be sure you are looking at the right pulley when you check it

cheapJeeper

Starter gear not disengaging completely, maybe ?

Does it change sounds between neutral and in gear?

cheap87

try checking the end play in the crank shaft. when the crank is cold the metal is retracted and the wamer it gets the more it expands. idk maby its a picky motor, i know my co-weorkers 4.0 dosnt run rough but he says it does but i think hes picky.

acermcgraw

Thanks guys, i am going to check the water pump today, however im not sure about that one no matter how much i like the idea of that being the issue. As far as the crankshaft is concerned, i just spent hours under the truck changing that harmonic balancer so im sure i would have noticed play in the shaft, and it was as tight as a drum

I just pulled the starter when i checked the flexplate and i had though wht if the starter isnt disengaging as well but i did a little test on it and it was working fine. so no go there either. Thanks for all the great ideas. Oh yeah it makes the noise in any gear , it has more to do with rpm then actual speed.

okcjeeper

Have you per chance checked the Catalytic converter? If you have a bad one it will make rattle noises..Mine is bad and it make sa god awful noise at startup till it warms up then it's find and I just hear my bad u-joints and motor/trany mounts..

milmat1

Mine drove me nuts last summer, Once the motor got warmed up it would periodialy start making a heck of a racket and shaking the whole front of the truck!
I finally found that the Aux cooling fan was missing a blade and when it came on it would sound like the end of the wordl