I have a 1992 300TE wagon that sounds like a bird chirping at times. Sometimes it is at idle, other times I can hear it at 15 to 30 mph. It does increase in frequency when the accelerator is pushed. It does not happen all the time, usually when my wife is driving it (but I have heard it too). Is it just a fan belt in need of replacing or something else?
Any hints would be greatly appreciated. Thanks!