Abstract: A valve actuating mechanism for an oil cooler bypass valve of the type in which a thermally responsive element expands to urge a valve member against a valve seat and thereby cause oil to flow through an oil cooler. A valve member is utilized which is movable independently of the thermally responsive element, and a relief spring is interposed between the valve member and the thermally responsive element to transmit expansion of the element to the valve member. The valve actuating mechanism is designed to allow oil to pass through the valve despite incorrect connections between the ports of the bypass valve and the ports of the oil cooler and oil source. In one embodiment in which the valve member comes into engagement with a valve seat, the relief spring is adapted to accommodate expansion of the element subsequent such seating whereby damage to the bypass valve components is avoided.