Have a '93 Honda Accord EX, 5 speed manual, ps, pb, ABS, air with 150K+. While driving and approaching an intersection, I applied my brakes only to have the brake pedal go to the floor. Pumping the brakes will not remedy the problem. This happened without warning (no dash signals, no brake squeeks). In diagnosing the brake failure, I have found the brake reservoir to be full, no leaks and no fluid on the ground. Also, if the car is not running, the brakes will pump up, however, when you turn the car off, the brake pedal will go to the floor. Any ideas?

 

Sounds like a bad Master Cylinder to me it happened to my wifes car 93 Accord SE

 

Before you take any thing apart Bleed the entire Brake system (Front and Back). It sounds like there's air in the system. Check for leaking brake lines and calipers. If that doesn't work pull the front brakes apart to see if the piston moves when the pedal is pressed and depressed possibly piston freeze. If this all passes then check your porpoting vavle for leaks and air bubbles, Last is the brake booster/Master cylinder.