Early 1984 Mustang GT with power brake booster.
Put car into storage 2 years ago, brakes were fine. Just took it out and the brake pedal is really low. Both fluid reservoirs are full, and the brake booster is working okay. all the wheels appear to turn and stop properly. I'm thinking the master cylinder is about to go. Does this sound reasonable?
Most likely cause is one or more caliper slider pins are sticking/ frozen, causing you to press further down before the pads grab onto the rotor.
If you really want to isolate the low pedal you can do an isolation test. You block off all 4 brake hoses by using the proper tool or 4 vise grips applied gently enough to block the flow though each hose. Start the engine. With all 4 blocked, the pedal should be rock hard and no travel. Depress the pedal slowly and hold the pressure easily for a minute or two. If the pedal remains hard, the master cyl if perfect and not bypassing. If it looses pressure, change the M/C.
If good proceed to do the following, open one vise grip or clamp. Press the pedal, noting just how low the pedal goes. Close that clamp again and proceed to do all the other wheels, one at a time. Eventually, you will feel a difference when you come across the wheel with the problem. At that point, look further at the caliper, pins, pads. You will find your problem if you follow this isolation method.
Of course, if you have rear drum brakes, they could be wore or out of adjustment, wheel cyl ng, etc.
Remember, there is a big difference between a low pedal and a sinking pedal. Sinking indicates a pressure loss. Know which one you are looking for before you begin.
Gary
