[DogMeister]

'67 GTO with '70 Chevelle 11" discs on the front, standard drums on the rear, 9" booster. All chrome booster/master cylinder/proportioning valve setup from CPP. The first setup was the 12" kit from CPP with 2" drop spindles. Had to change them out because the drop was too low. All new lines and hoses, ceramic pads.

On both setups, the discs drag, are not retracting/releasing, whatever you want to call it, they're not letting go, to the point that they get hot and the car cannot be pushed in neutral. They release after an hour or two. The first rotors got so hot they turned blue.

I'm thinking it's the proportioning valve or master cylinder, or I guess it could be the booster. What do you guys think? What can I check? 300 miles on the car so far, less than 100 on this current set. The brake light switch is not putting any pressure on the pedal. There's a hex nut on the front of the prop valve. Is that an adjustment?

[Scarebird]

1. How much slop is there in the pedal push rod?
2. If the rod is slightly loose (as it should be), back off the nuts holding the master to the booster a few turns, see if the wheels turn.

[DogMeister]

There's enough slop to see that nothing is keeping the pedal from returning. What will loosening the mc cylinder nuts tell me?

[Lemans64]

Loosening the nuts on master cylinder will show if the pushrod between the master and booster is correct, or if booster is pushing on master.
If brakes release after loosing nuts at master, the booster is pushing on master, not allowing master to return completely, holding pressure in front lines.
Is this stuff all new?

[DogMeister]

Maybe it is. Maybe I've never had to diagnose an issue with power brakes. Thanks for your help.

[PontiacHO]

Some booster to master cylinder rods are adjustable. If so, shorten the rod some.

[Cammer-6]

is it a drum brake MC?
If so thats also a problem