How does a bypass valve work on a thermostat?
How does a bypass valve work on a thermostat? But a completely separate spring loaded bypass valve (B) independently controls the bypass. The way this works is that when the thermostat is closed, it arrests flow, which creates a local area of high static pressure. This pressure opens the bypass valve, allowing coolant to recirculate to the pump (P) and back to the engine (E). What was the bypass on a Cadillac thermostat? The bypass in this early Cadillac comprised a small tube leading from the carburetor water jacket to the pump inlet. This was sufficient to provide some circulation...