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Discussion Starter · #1 ·
Just converted a 57 Olds to 4 wheel disk. Used kit for the front, chev calipers, fabed bracket for rear, t-bird caliper, and used 90's caprice 4 whl disk mast. cyl.
When trying to bleed the brakes, I can only get the rear portion of the mast. cyl to work. It seems to bench bleed fine, but when installed in the car the front portion of the mast. cyl goes dead. I thought the mast. might be defective, so I sent it back and got a different one. Same problem. There is no combination valve in the car. Could that be a problem? Is my master shot? It's all I can come up with, but I'm not a pro.
 

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I am using that same MC on my s10 with 12" b-body brakes up front and 2000 blazer discs in rear. I have no combo valve but I do have a Wilwood adj. prop. valve. It works better then just about any vehicle I have ever driven.

How do you have the MC plumbed?
The front port on the MC goes to the rear brakes and the rear goes to the front brakes.
 

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Discussion Starter · #3 ·
That was how I hooked it up. The front brakes worked great, but I couldn't get the back to bleed. I swapped the lines on the master cyl. to see if there was anything wrong on the rear,{plugged line,etc.} and then the rear worked fine and the front brakes wouldn't bleed.
 

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I'm sure this link is way more simplistic than what you already know, but it might give you some clue as to what is going on. Activate the arrows to show what happens when there is a leak in one of the two sections of the brake system.

http://auto.howstuffworks.com/master-brake1.htm

My first thought was that you might have a missing or broken spring between the primary and secondary pistons of the MC, but since you swapped in a brand new one my next guess would be a leak in the line between the MC and the combo valve.
 

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Caprice is probably a Quick Take Up master, which can be finicky.

Bleeding directions on them usually say to use single stroke method, and wait 15 seconds between each slow pump of the pedal.

I have had luck just bench bleeding them, and then gravity bleed for a while, close it all up and it's done... because if I touch the pedal to bleed according to instructions, or otherwise, the rear brakes suck in air somehow, more on some models than others (trucks).

I've also had luck syringe bleeding or pressure bleeding brakes with those masters.
 

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Discussion Starter · #6 ·
Rebled the brakes with a mighty vac, and set up the pedal for a bit of additional travel[ It was only moving the pushrod 3/4 of an inch] Don't know which one fixed it, but the brakes work great.
 
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