I have an 89 s10 4.3 4x4 which has been running great. The other day when I went to start it up I heard what sounds like a vacuum leak or hissing air sound. Ive checked under the hood several times and can't find where it could be comming from. It really seems like it comes from behind/inside the dash. When I turn off the truck it (the hissing sound) slowly dies down and stops prob after about 10-15 sec after the truck has been off. The only thing that has made a difference is when I move the switch for the heater/ac vents. ie. from floor to vent, to defrost. I have found a place between the two where the sound seems to be the quietest. When turining on the heat it works fine but there are two distinct sounds one from the heater, and still the hissing sound. Truck runs good and haven't noticed anything wrong with it performance wise. I just dont like having strange sounds. Any help?
- posted
17 years ago