on my 2000 f150, the engine is making a loud whining sound. it only does it when the temperature outside is about 50 or below. is this a sign of just a bad serpentine belt, or something worse like perhaps one of my pumps going out or locking up. i used to have an 86 mustang gt with a 5.0 in it. one time the pollution control pump was going out, and it made a very similar sound to what i am hearing on my f150. instead of replacing the pump on the mustang, i took it apart and gutted everything out of it. so it was pretty much a useless pump.maybe my belt is just worn??

 

Could possibly be the belt tensioner or the belt idler pulley or both.

 

would it be because they might be loose? or possibly worn? truck has 130K miles on it

 

Possibly both. I got my tensioner replaced when I had the oil changed last (at around 67k)

 

My '93 has been doing the same thing lately it's gotten cold, sometimes sub-zero temperatures. It's not a constant whine and varies in volume from barely audible to a screech to loud I can't hear the radio anymore. Seems to go away when the motor warms up. Nothing seems to trigger it. Revving the motor does not cause it, neither does acceleration, coasting, shifting, nothing. I haven't noticed any performance problems.

I didn't figure it was serious but I would like to know what's causing it.