Duel Master Cylinder Help

[010175]

I was hoping someone had rebuild their MC. I need to know if there is any check valve (ball and spring) in a stock 1962 Cadillac master cylinder. Our problem is the new disk brakes will not release when brake pressure is applied unless one of the lines cracked are open to allow the brake line pressure to bleed down. ABS brakes (kit company) say that their is a one way check valve in the master cylinder that will not allow the brake pressure to bleed back into the master cylinder. I called the rebuild company that rebuilds the master cylinder and they said that they don't put back in the check valve because it not need. Our problem is definitely brake pressure that is not allowed to bleed off. The only other thing might be the proportional valve that we put in. I don't know how that valve work or if it have a check valve that might be bad. If this master cylinder has a check valves by the two brake line exits how would remove them? Thanks Dave

[MT-2500]

Make sure the booster plunger is not holding pressure on master cylinder.
Loosen up master cylinder bolts and see if it releases.

If not that get another mater cylinder.

[maxwedge]

The only time a residual check valve is needed is when the m/c is mounted under the floors like a street rod, or for drum brakes. MT2500 is right on the money with his advice, most pushrods out of the booster are adjustable, you cannot just bolt on the m/c. Also I assume you have plumbed in a proportioning valve as required. You should have the residual valve in the portion of the master for the rear brakes. Make sure you have the lines connected to the right ports on the m/c.

[010175]

Thanks I know i have the plumbed the wrong ports out of the MC. I did not think it would make a differnace. Does it and why? Thanks Dave

[maxwedge]

It may if the reservoirs are different sizes, number one, if they are there should be a residual valve for the rear brakes built into the proper port for the rear. Is so that could hold your discs on, you can tell if there is one, by disconnecting the line from the m/c, insert a 1/8 drill lightly into the m/c port and see if you feel a spring loaded resistance, that is the residual valve.

[010175]

First Thanks to both of you guys. I removed the MC and found the check valve. I used a sheet metal screw that just started in the small hole and washer to make a puller out of. I pulled the brass tip out of hole and removed the rubber valve and spring. Re plumbed the MC so it now right. Blead and test drove the car and now the Disk release as they should... Thanks again Dave

[MT-2500]

You are welcome and thanks for posting back how it went.
Good Luck.