Valve construction having multiple piston means and method of making the same

In a self-contained temperature responsive valve construction having a housing means provided with a pair of ports separated by a first valve seat means that is opened and closed by a valve member means in response to temperature sensed by a piston and cylinder type temperature responsive device carried by said housing means and being operatively associated with said valve member means to control the same through axial movement thereof, the improvement wherein said housing means has a by-pass passage means therein separate from said valve member means and adapted to interconnect said pair of ports together independently of said first valve seat means when said first valve seat means is closed by said valve member means, and a one-way check valve means carried by said housing means and being separate from said valve member means for controlling said by-pass passage means to permit fluid flow between said ports through said check valve means in only one direction, one of said ports being disposed intermediate said first valve seat means and said one-way check valve means, said housing means having a second valve seat means disposed intermediate said one of said ports and said one-way check valve means to be controlled by said valve member means.