Brake pedal

Is there a return spring on the pedal ?

Chuck

Yes, there is a return spring. Let me try to explain a bit better. The pedal seems to have a normal height bost of the time and the brakes seem fine then. When this problem happens the pedal appears very firm and braking starts at a much higher pedal point. It seems very odd, but then I am not sure what is happening.

Your brake pedal height growth is undoubtably caused by the rod between the power brake diaphragm and the brake master cylinder being slightly too long. This causes a little mismatch with the bleed-back port in the master and consequent caliper drag. The caliper drag heats up the brakes and fluid, and you detect this by the pedal moving up. In really bad cases, the pedal travel will top out under your dash, the calipers will lock and you'll be alongside the road until things cool down. Do not ask how I know this! To fix: with the brakes stone-cold, unbolt the master cylinder from the power unit. Note if the master cylinder springs out a bit when unbolted, or stays absolutely flat against the power unit. This distance is what you must trim from the loose rod inside, maintaining the rod's rounded end profile. Or, a pair of washers the exact right thickness between the power unit and master cylinder (around the studs) will also work.

Ok, I can understand that part. But how is it that this rod is just a hair too long?
Why does it only happen sometimes, and not always? Time to go try your fix. Thanks.

The rod has an adjustable end on the front. It takes a very, very little amount of rotation to make a difference in the rod length. Be super, super careful with the seal in the front of the booster they do not make them anymore.

Mike