Abstract: A fluid pressure actuated by-pass valve and relief valve are positioned between a source of fluid under pressure and the hollow interior of a rotor in a fluid pressure actuated downhole drilling motor. The valve includes a hollow mandrel with an inlet opening at one end and an outlet opening at the other end connected to the rotor interior and slidably received in a movable sleeve. Fluid pressure at a first predetermined value moves the mandrel into the sleeve to block the inlet opening such that the fluid by-passes the valve and flows between the stator and the rotor to rotate a bit. Fluid pressure at a higher second predetermined value moves the sleeve relative to the mandrel to expose the inlet opening and relieve the fluid pressure on the rotor and the stator. The movement of the sleeve exposes a greater surface area thereof to the fluid pressure such that a spring moves the sleeve back to block the inlet opening only at an intermediate third predetermined fluid pressure value.