Serpentine belt noise

I have a 2002 Chrysler Voyager with 135000 miles and in good shape. My mechanic has replaced the serpentine belt 3 times in the last 24 months each time using a different manufacturer. The last time was <6 months ago. The tensioner pulley was replaced 10 months when the screeching noise returned as it has each time the belt is replaced. The other pulleys all seem to work fine. I use a small fingernail sized dab of NAPA’s “Sil-Glyde” lubricant on the underside of the belt every 150-200 miles. I will use it more frequently if it has rained recently.

-AC works fine and is not associated with this screeeching
-PS pump works fine and shows no leaks. Rack has been replaced. PS fluid system flushed and filled with new fluid.
-Alternator runs fine


First stop using the lube on the belt its not needed and may damage the belt. Next all the pulleys need to be checked for alinement and their bearings checked also.

I’ve had good luck with Goodyear Poly-V belts on my vehicles, especially my 2000 Blazer with is noisy with any other brand. Is it possibly one of the pulleys is binding?

Ed B.

Thank you both. I will tell my mechanic about the poly-v belt. The good news is that he has replaced the belts free of charge because they have not remedied what has proved so far to be undiagnosable.

Ditto on the alignment suggestion.
@oldbodyman: That little dab of Sil-Glyde works immediately and lasts 200 miles unless it rains. NAPA claims it is safe for serpentine belts - it is silicon based not petroleum based. The only danger comes from too much lube causing the belt to jump out of the pulleys. I am judicious in my use. I would rather fix the problem all together.

  • My mechanic and I have used sound rods on the pulleys to try to identify if bearings are bad. No luck with that one - if bearings were bad the Sil-Glyde would not help.
  • This sounds right: Aligning pulleys makes sense but I’ll just have to figure out how. The screeching is not noticeable at idle and builds as rpms increase (makes the sound rod test hairy).

Has the mechanic tried rotating various pulleys on different accessories with the belt in place to make sure the pulley is actually getting a good bite on the belt?
A pulley should be difficult to turn by hand with a small ratchet/socket.

Sometimes the ribs on the pulleys can wear down and this can prevent the belt from grabbing onto the pulley firmly. A little special attention to the alternator pulley might be a good idea.

I had a Dodge Caravan and the stock tensioner was always a weak spot. The third time it went out I had a Goodyear Accu-DRIVE tensioner installed and never had a problem afterwards. This is one time where an aftermarket part was superior to the OEM part.

Get an automotive stethoscope and probe around to see if you can pinpoint that noise.
Maybe one of the things on the belt has a bad bearing.

You shouldn’t have to use goo on your belt.

You lubricate your serpentine belt every 150-200 miles? No WONDER you’re having trouble!

Bottom line: you should NOT be lubricating your serpentine belt. For a serp belt to operate properly you NEED FRICTION. Lubricants REDUCE FRICTION. Silicone lubricant reduces friction very well. BAD for serpentine belts.

The Sil-Gel manufacturer says it is safe for serpentine belts meaning that it will not harm serpentine belts if you use it elsewhere and accidentally get some one the belt. They’re not telling you that it should be used on belts.

My recommendatiob is to clean your pulleys with a citrus-based cleaner, rinse well, then install a new serp belt and never again lube it. Ever.