COOLING SYSTEM WING NUT ON TOP OF THERMOSTAT AREA WHAT IS PURPOSE

[buick special]

Hi Guys

   I was giving the 1940 special another look over and noticed a small wing nut type knob on top of the thermostat

 

where the 2 hoses go out to travel into the passenger interior

 

anyone know its function?

 

 

I am giving a wild guess that it is a shut off valve for water going to the heating core

 

I noticed there are no switches in the cabin nor a blower to activate heat so am guessing this is a real economy way to do it?

 

 

is that what the wing nut valve near the thermostat is for?

[Guest]

Yes, that is the water shut off.  Most pre war cars had one as did many up into the early fifties.  Then GM at least started using "Ranco", valves to the joy of parts departments (late fifties, sixties and seventies we sold thousands of them).

[MCHinson]

Yes, that is the valve so you could stop hot water from going to the heater core during the summer. The car should still have a fan switch somewhere for the heater. You would not use the water cut off valve to turn the heater on and off in regular use.