I replaced both tensioner pulleys and the belt (I even tried the shorter belt, bypassing the AC compressor), with no change. In fact, the whining squeal (for lack of a better term) is louder than ever.
Also: I've noticed that the noise is more insistent, more strident, after the truck is first started in the morning, when the ambient temperature is lower, after being parked overnight. After shutting off the engine for a few minutes and re-starting, the noise disappears, only to re-appear after a few minutes. Later in the day, after the ambient temperature rises, the noise becomes rather erratic and unpredictable, and will even stop occasionally, only to reappear later.
With no "check engine" light and no other indication of a problem, I'm at a complete loss.
Wednesday, May 28th, 2014 AT 1:09 PM