[harryx]

My brake pedal went to the floor with no resistance. When I turned the truck off, I had brakes again. The fluid level is fine in the master cylinder. I disconnected the vacuum going to the booster and now I can drive again. It certainly appears the booster is bad and I will replace it, but is this a normal symtom of a bad booster? I did try to connect the vacuum hose later and got the same problem, brake pedal to the floor.

[LATECH]

So are you saying you have driven the truck and the brakes will stop it?
The pedal should not go to the floor... running engine or not. If it does with the engine running maybe the master is bad and it just feels like you have brakes with the engine off when the booster looses power to assist. Something doesnt makes sense here.

[bigdog7373]

If you are having problems with the brakes then stop driving the truck! Get it fixed and working first. No need to risk your life for a brake booster.

[harryx]

First, I am not driving around with this problem. I am testing the brakes in my driveway. The brake pedal is now going to the floor without the vacuum line. If I pump the pedal for awhile it starts to get stiff, but if I start the car with the vacuum line connected it goes right to the floor. I think I need to first bleed the brakes, and hope the master cyclinder is not bad.

Now, I don't think the problem is with the booster.
Thank you for the replies.

[harryx]

I replaced the master cylinder and I still had the problem with the pedal going to the floor when the truck was running. I then replaced the after-market pancake style brake booster with a re-conditioned 1974 Corvette booster. and my problem was solved. I can't believe a booster not holding vacuum can cause such a severe problem.

[fast68]

yep, its because it was ruptured internally and vacuum was on wrong side of it internally, working against your foot pressure

most boosters are hard as a rock when failed/ruptured,

makes perfect sense


it failed

have fun!