I have a 2001 2500 diesel with a hell of a screeching sound coming from a pulley or belt. I tried belt dressing--no help--however after spraying WD40 on the back of the tensioner pulley it all went away--bad pulley right! I changed the tensioner pulley & it still made the sound--sprayed WD40 behind the tensioner pulley & silence. It is quite until the WD dries up & then the screeching starts again.

My neighbor has a 2000 ram 318 ci and he has put a new idler pulley on, new belt, new tensioner pulley and can't get rid of his noise either. He has the same deal--sprays some WD on the tensioner pulley & it all goes away until the WD dries up.

Can anyone solve this mystery---we are going nuts? We replace the tensioner pulley, but that does not help--WD on the pulley & the noise goes away for a little while???????????????????????? Are both our Ram's haunted or what?

 

I would come closer to thinking that when you spray that pulley, you end up getting oil on the belt and it is moving the lubricant to the location of the squeal.

My guess would be the water pump. They like to start chirping when they go bad anyways. I know about a year before mine went bad, I had an annoying chirp chirp at idle with mine and I drove myself nuts trying to find it. Wasn't until the pump was puking out coolant and water a year later that I made the connection.

 

I was hoping it was not the pump, but that seems to be the only explanation. Thanks for your advise.

 

So you replaced the pulley and not the tensioner itself? I just changed mine the other day because it was clicking and clacking at idle.
You should get a mechanics stethoscope (3$ at harbor freight) or a metal rod that you can press to your ear and poke around the engine to see if you can locate the squeak.