Serpentine belt squeak

[69427]

Could it be an alignment issue? Just thinking that a slight misalignment of one of the pulleys might cause uneven tension across the width of the belt. Haven't noticed any alignment issue. It's the stock setup with 140k miles.

Does the backside (flat) of the belt wrap around the water pump pulley?

Yep, the pump pulley gets its drive from the back side of the belt. I've kicked around the idea of (temporarily) trying to stretch a loop chunk of an inner tube over the pump pulley to try to get a better grip surface on it to eliminate any belt slippage but I don't know if I can stretch it across the fan blades first.

 

[MYBAD79]

I'm still saying it's most likely the tensioner..... autoZone or Rockauto.....

But there's another possibility (this happened to me once ).... If you have a very small leak at either the water pump or maybe at the heater hose and if you get a little bit of coolant (antifreeze) on the belt it will sqeeek like a pig..... Or worst case lip off the pulley....

This is not a very likely scenario but it really fits your symptoms..... Once it heats up and builds pressure it leaks ..... A drop is enough to make the belt sqeek......