Hissing Sound From Brake Pedal ??
My 1991 F-150 sometimes makes a "hissing" sound that comes from down by the brake pedal when I depress it. This doesn't happen all of the time, but just "sometimes". Sometimes it only hisses as I depress the brake, and sometimes it hisses all the while I have my foot on the pedal. Sometimes it doesn't do it at all.
Through all of this my brakes appear to work normally, with no increase in pedal pressure. If this is the power brake vacuum booster, approximately what does this run, parts and labor to have replaced? Has anyone had this problem in their truck?