Brake Gurus?
 

I'm stumped. Rebuilt all my calipers with VBP O-rings and new master cylinder. No problems for two years. Yesterday, pedal goes to the floor (Scary Chit) No fluid in front circuit. Bleed system, check for leaks...None. Go for a drive today, brakes are all good. Suddenly, pedal is hard (Will not move more than 1/4 inch) and feels like no front brakes. (Another scary moment) Plenty of fluid. Any suggestions?

Master cylinder leaking a rear seal going into braker booster . Fluid being sucked into motor via vacuum .

Why would that cause the rigid brake pedal?

I have a '75 and my brake pedal became very hard in the last two days. Hardly no brakes. As I was looking at the master cylinder and brake booster, I saw a hose from the booster to the carb. Why do I need brake fluid going to my carburator? You guessed it. I"m not a gearhead, but I've learned a lot on this Forum.

zzyzx,
Sounds like a definite master cylinder failure. The missing fluid from the front circuit had to go somewhere. If the calipers are not loosing fluid, one or more seals in the master cylinder probably failed and pushed the fluid to the other circuit. Normally, a super hard pedal is a sign of the booster failing but the system will have a similar hard pedal with no fluid in a brake circuit. Hope this helps.

KALAWAY,
The hose from the booster to the carb supplies vacuum from the engine to the booster. If the booster is leaking vacuum, you will have a very hard brake pedal and it will be virtually impossible to stop the car. Hope this helps.

Sincerely,
Alan G.
Vette Brakes & Products, Inc.
http://www.VBandP.com
800-237-9991

Yes it does. Thanks for your advice, and the great products you supply. The O-ring kit was yours, not the master c. I always thought an empty circuit (Especially front) gave a push-to-floor-feel. How do I diagnose if it is booster, or master cylinder? After two white-knuckle moments, I am gun-shy.

I was told to start the car, then remove the hose from the booster to the intake. Put your hand over the end of the hose. If you have good suction, then the booster is bad.(?). I had suction.