NOTE: Brake booster failures often cause a hissing noise to occur up where the booster goes into the firewall. The hissing noise comes from a vacuum leak that is created in the booster itself. The pedal also typically gets hard. Check the part number on your part prior to ordering
NOTE: Brake master failures can often be identified by noting that the pedal may go all the way to the floor slowly. This is an indication that the seals are worn in the master. Success in Rebuilding depends on the condition.