We were planning to go for a drive in our 1954 1/2 ton today. I started the truck and moved it out of the garage. Tried to stop so we could close the garage door but the brake pedal goes to floor like there's nothing there. Fortunately, the driveway is level so it just rolled to a stop. Pumping brakes did not bring pedal up.

* Truck has power brakes with booster and dual master cyl under the floor.

Checked pedal linkage. Pin was OK and secure. Link and return spring were Ok. Input rod on booster moving in/out as expected as pedal pushed and released.

Checked brake fluid level. Both reservoirs were full. I expected this as I didn't see any signs of leaks.

With engine running, brake pedal goes to the floor easily. With engine off, brake pedal goes to floor with a bit more effort. If the booster was gone, the brakes should still work but with more effort.

My conclusion is that master cyl has to be replaced. Reasonable conclusion or did I miss something?

Gord 🇨🇦
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1954 1/2 ton 235 4 speed