brake pedal sticks only when car is hot
 

Camaro Guru's

Scenario:
I have a 1968 Camaro BB 396 Power Disc brake car.

I bought a 7" power brake booster and master cylinder combo from ebay and installed in on my car.

When the car is cold, the brake works fine and doesn't stick. Once you drive the car a bit 10 - 15min and it generates some heat, the brake pedal sticks down when pressed. At this time you have to slide your foot under the pedal and pull it up. This becomes a pain if you get in a bit of traffic down in south Florida.

I even tried to put a return spring on the pedal to improve this but still no luck.

Any ideas for problem solving or even some troubleshooting tips would be greatly appreciated. Has anyone ever experienced a similar problem or heard of this before.

Thank you for your help.

68CamaroSFL

If the pedal is dropping, to where you don't have enough travel left to stop, then it sounds like you need to bleed your brakes some more.
Did you bench bleed the master cylinder?

Clarification
 

Sorry for the confusion, the brake pedal has full travel, just when the car gets hot, the brake pedal goes down normal throw and stops the car it just doesn't return. The brakes are bled all the way around.

Forgot to mention that the proportioning valve is old and hasn't been replaced in years, not sure if this could have an affect on it.

When you apply brake, I almost here a rubber rubbing sound, but not sure.

Sounds to me like the master cylinder may have an issue. I am picturing in my head the valve gaskets being too large for the shaft but only bind after the heat from the engine warms it up. I am not a brake expert but my guess is that this condition will lessen with time. Monitor it closely and try to see if doubling up on the return spring for the brake pedal will make the issue appear to go away.