low volume chatter or rattle coming from front of engine, that has a cyclical rythm..

[McQue]

2001 XJ 4.OL AW4 all stock, aprox 84K miles Daily Driver.
SYMPTON...low volume chatter or rattle coming from front of engine, that has a cyclical rythm... 3 to 4 seconds of normal sound, then the chatter or rattel starts for about 1 to 2 seconds. Not using A/C or defrost mode either. When you hear the noise, you can see the serpentine belt alter its tracking just slightly on the fan pulley, idler pulley and at the A/C pulley.
Running engine without the serpentine belt will not produce the problem.
Rotated all pulleys by hand when belt was off and they all seem to rotate freely and in correct alignment.
Listened with a stethoscope at Idler pulley, P/S pulley and Idler pulley and Water pump, and the noise resonates the same at each pulley when it occurs.
Noise does not match cycle time of viscous fan when it engages and disengages.
A/C, alternator, power steering, cooling system. and motor performance all work as normal since day one when vehicle was purchased new.
Belt tension has been checked with Krikit guage and is correctly adjusted.
I have been driving it daily since the noise suddenly appeared last fall...problem has not gotten any worse or better...volume of sound has not increased.
Was hoping the sympton would change and lead me to the problem but no change for last six months. I am ready to try shotguning some parts.
What would you try first? second? third?

 

[winterbeater]

I don't think it's likely on yours, but have you looked closely at the harmonic balancer? If you search, you can find threads where they are coming apart.

 

[98 jeepjeep]

lifter tap maybe?

 

[joe_peters]

Take a broader approach to listening to the engine.

Buy some clear vinyl tubing, about 3ft. Hold one end in your ear and move the other around the front of the engine listening for the sound. You could pull the end from the mechanic's stethoscope but that doesn't leave much tubing for reaching around in the engine compartment.

Don't throw parts at it. Throwing parts at an xj is like trying to teach a pig to sing--it is a waste of your time and it annoys the pig.

 

[logdog]

Water pump bearings

 

[McQue]

I have inspected the Harmonic Balancer and it appears to be in fine condition.
The noise goes away when the motor is running without the serpentine belt so I can't see how it could have anything to do with lifters...
My mechanics stethoscope gives me 3' feet of reach already and I have used it to listen to every assembly...problem is the sound resonates the same throughout all assemblies with a pulley. I will ask another mechanic to listen to what I am hearing to get a second opinion.
My Jeep is functioning normally as far as cooling, charging, power steering, air conditioning, and motor performance...so I am going to keep a close watch on the problem with the hope that something changes to help me isolate the problem.

Thanks for the opinions...best regards, McQue

 

[joe_peters]

McQue--The metal end of the standard mechanics stethoscope will pick up sound transferred through the metal. Using the plain vinyl tubing, which you don't press to the metal, will not.

Once you have isolated the locality of the front of the engine where the sound is loudest, you have a lot less items to physically inspect.

Good luck.

 

[McQue]

ok...now I understand what you are suggesting...will give it a try.

 

[McQue]

just want to close the thread out with this update... the noise I have been chasing for the last 2 and half years turned out to be my A/C compressor... replaced it today... all is well