67 brake issues- need brakes experts

[Bob H.]

Replaced master cylinder and booster 3 years ago and have had no issues until a few months ago. Had great brakes but noticed the pedal seemed to have gone down a bit but still had great brakes. Didn't drive the car for 6weeks and now the pedal goes all the way down and brakes are slow to work. First I re-bled them with no change. I finally figured out I have front brakes and no back brakes. I then noticed when pumping the brakes hard fluid shoots up the hole in the front reservoir but little flow from the rear one. During this pumping of the brakes I noticed the fluid in the rear reservoir was going down. When we stopped pumping, all the fluid came back into the reservoir. I understand there must be air in the rear but where it is and how it got there I don't know. Why would the fluid return to the master cylinder? Do I have a bad master?

[Marco H.]

Re: 67 brake issues- need brakes experts

Bob,
This sounds to me as you have a internal leak in the master cylinder. The '67 Corvette has a brake block below the MC which is designed to "block" the circuit that has pressure loss. It appears as in your case the pressure in the front circuit moved the plunger in the brake block and restricted flow to the rear. I would go through the MC and also disassemble and clean the block (Center post, where tan wire is attached can be removed for flushing, and new o-ring installation.)
Hope this helps,
Marco

*** I am assuming, you checked all the calipers, hoses and line connections for leaks.

[Joe L.]

Re: 67 brake issues- need brakes experts

Replaced master cylinder and booster 3 years ago and have had no issues until a few months ago. Had great brakes but noticed the pedal seemed to have gone down a bit but still had great brakes. Didn't drive the car for 6weeks and now the pedal goes all the way down and brakes are slow to work. First I re-bled them with no change. I finally figured out I have front brakes and no back brakes. I then noticed when pumping the brakes hard fluid shoots up the hole in the front reservoir but little flow from the rear one. During this pumping of the brakes I noticed the fluid in the rear reservoir was going down. When we stopped pumping, all the fluid came back into the reservoir. I understand there must be air in the rear but where it is and how it got there I don't know. Why would the fluid return to the master cylinder? Do I have a bad master?

Bob------


When you bled the brakes did you bleed BOTH bleeders on each rear caliper?

[Bob H.]

Re: 67 brake issues- need brakes experts

Joe:

How insulting to a guy that has owned 20 plus C2 and C3 Corvettes and performed dozens of brake jobs! And thanks to you I made reservations to move to assisted living since I forgot the outside bleeders. I think my mental block did have something to do with regard to having to take off the starburst centers. After removing the wheel I found a seeping caliper that was undetectable from the inside. I don't know whether to thank you or just complain about the food here at assisted living.

Bob

I can't count the times I asked others the same question.