The '41 Chevy sedan I bought last month has power 4 wheel disc brakes on it with the booster and master cylinder mounted under the floor in the stock location. When the car is first started and for ten minutes or so afterward, the brakes function and the pedal returns just like it should but then it begins to fail to return. A little at a time but within a few miles I have to hook my toe under the pedal and pull it up to release the brakes. The brakes work entirely normally except for that issue. Anybody got experience with this problem or something similar?