Half way through my Sunday afternoon drive I developed a brake problem in my 86 Corvette convertible. I went to stop , the car stopped but the brake pedal suddenly felt spongy and slowly sank to the floor. The brake warning light also came on when the pedal got to the floor. I pumped the brakes, the warning light went off and the brakes worked normally. However if I held my foot on the pedal it would go to the floor and the light would come on again. I made it home without incident by pumping the brakes each time I needed to stop.

When I was home I immediately checked the reservoir for brake fluid and it was full! I checked each wheel and the area around the reservoir but could detect no sign of leaks.

My gut instinct tells me that the master cylinder has failed. I would like to confirm this with your experiences before I order a replacement Master cylinder.

Thanks for any input you can give to me. 

Thanks to you all,

It was the master cylinder, I replaced it with a new one bled the brakes and now all is functioning as it should.

Red said: