HELP! BRAKES DO NOT WORK!

[sheeneng]

I have a 1991 Nissan 240SX coupe. Stock Dual cam engine. My brakes are not working correctly. At first, I would be able to be able to use my brakes but would have to press down til about half way to get the brakes working. I heard air hissing noise when pressing them so then I bled them. I bled them all and then I couldn't get any brakes at all. When the car was off, I would get some resistance on the brakes, but once I turned the car on, no pressure and straight down to the floor. So then I bought a new master cylinder and bled my brakes but still the same thing. No brakes. There is a air hissing noise coming from under where the brake pedal is located and can hear it coming from brake booster in the engine bay. Any suggestions on what might be wrong? Thanks!

[CSUPUEBLOTIM]

The air is more than likely the brake booster...normal. Sounds like you still have air in the lines. did you bench bleed the new master cylinder and how are you bleeding the brakes?

[sheeneng]

I did not bench bleed the new master cylinder. I don't have a clamp or the rod to do this. Do I just keep bleeding my brakes all around until no bubbles? Also, what method to use when pumping? Do I pump, pump, pump, hold down or should I push down slowly, open, and close right before brakes hit the ground

[CSUPUEBLOTIM]

Its a two man job unless you have a handheld bleeder. During the process always make sure you never run your master cylinder empty. Pump the brakes up until the pedal gets hard and hold. Have somebody open the bleeder at the caliper. Continue to hold the pedal until it falls to the floor. Hold it there. Your buddy will then close the bleeder. Once closed then you can release the pedal. Repeat until no air is in the line (solid stream). Using a clear piece of tubing over the bleeder and a pan to drain it into is easiest. It will probably take awhile since it was not bench bled. Once all the air is out. Make sure the master cylinder is full. Start the car and see how the pedal feels.