ImperialCrown· Super Moderator
1966 Crown Coupe, 2016 200 S AWD, 1962 Lark Daytona V8.
The coolant return poppet valve (the one in the center of the rubber washer) should allow coolant to flow from the reservior to the radiator, but coolant should not flow from the radiator to the reservior by squeezing the upper hose. Debris in the coolant like gasket shaving material or stop-leak or anything that floats to the top of the coolant can cause this poppet not to seal well. The coolant must be clean.