Tmello401

I have a 1996 12v cummins with 196k miles on the clock. Just last week the truck started squeaking but barely noticeable. This week it is actually up more and more, becoming louder. The water pump is brand new and the serpentine belt is brand new. The alternator is approximately four years old. I am thinking it could be the alternator or the pulley tensioner, anyone with any insight is greatly appreciated, thank you. I took a video and of course it will only allow pictures

texasprd

Alternator and tensioner are certainly frequent suspects. The fan bearing sometimes fails, too. AC compressor is a possibility, though that tends to be more of a rattle or tinkling sound - and it will probably only be when AC is on. Basically, anything belt-driven is a suspect.

Can you localize it to one side (or center)?

Have you tried using a mechanics stethoscope or a screwdriver to the ear to locate it? The other method (pretty much limited to alternator and tensioner pulley, due to fluid resistance on the others) is to take the belt off and spin the particular pulley as hard you can by hand and see if it squeals....

APD

Probably the new belt.

A quick test is to spray some belt conditioner, or even water, on the belt while its running and see if the sound changes.

My new belt is squeaky at times too, usually just when cold or wet. After it warms up no more squeak.