I second tom w. This usually happens when you are light on the brake pedal...Right? When you push the brakes moderate to hard the car stops ok....Right? If this is so, what is happening is when you push hard the master cyl cups expand to seal in the m. cyl. bore. when you apply light pedal, the cups will let fluid leak past.

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My Truck.. 2007 DODGE, 5.9 Cummins, 6spd stick, 4X4. My car..1977 240D, OTHER WHEELS...1955 VW Oval window bug, European Delivery (Holland) with a 1700cc, 2 barrel, Porsche drum brakes. 1939 WILLYS Pick-up. 1967 Triumph 200cc Tiger Cub. 1976 Honda 550F 4cyl Motor Cycle.