My 70 Cuda has sat outside with the parking brake on for about 8 months and now that it is back up and running I am having a problem with the brake pedal which is not returning back to the top position.

I changed the master cylinder (because it needed it anyway) and bled the brakes. The master cylinder change out did not solve it, but the rear brake bleeding seems to have fixed it but only when the car is off. Once i started it and the power brake assist worked, it didn't return again. In all cases I have to help it back up using my foot under the brake pedal. Bench bled the master cylinder and it returned great.

The car has front power disks and rear drums and are all factory and replacement parts, no upgrades. It has the original brake lines.

No hissing from the power booster and everything under the brake pedal seems intact.

I will be changing the rear brake springs and will also bleed the front brakes.

Any other ideas?

Thanks!

Could be that the rear brake hose has collapsed internally. I saw that recently when the rear brakes(drum) locked up.

booster.

try and remove the vacuum line and see if it comes back up. if it does, internal value in the booster has stuck or going bad.

I tried this and brake pedal did return, so I'll change booster out and report back.
thanks!