In Reply to: What is that #$@*! Humming Noise!? posted by Kirk on October 06, 1999 at 10:41:03:
Some pullies make similar noises and could be belts. You also have an electric air pump and some sort of switch or diverter valve (I forgot the name) connecting to that and on your exhaust manifold. You can see a diagram on it on your drivers side shock tower as well as emissions information. Fuel EVAP could be letting in fuel vapors in your intake..not so sure if that makes noise. Engine Fan really shouldn't engage itself but could be a test to see if it's working.