In Reply to: What is that #$@*! Humming Noise!? posted by Kirk on October 06, 1999 at 10:41:03:
I think the extra fan and hose is for air injection to the exhaust which helps reduce emissions when the engine is cold then shuts off by thermostatic switch. Could be what you hear. Does it go away when the engine gets warm?
: This morning I was in the parking lot with the engine running, radio off and fan off and all I could hear is this humming noise. It had a higher pitch too and it wasn't that subtle. Revving the engine did not change its pitch and as I said I had no accessories running. This has happened intermittently. It was a little cold this morning (45 degrees), but I don't think weather is a factor. I did a walk around the car and could hear it more towards the right front, but not as loud as it was in the car. The car is a stock 99 with 6400k on it. Any ideas?