Originally Posted by TKruger
I have a 1941 Master Deluxe (yes I know it is a car but after looking at other forums I am going to where the best place to go for advice on these motors is).
Question #1:
I and my sons are putting it back together. After installing a new water pump I installed a new thermostat. Not sure if I put the right end up. I placed the spring down and bolted it back together. Then I thought well that does not seem right.

Question #2:
We have run the motor but not for more than 20 minutes at idle. The heater hose is looped back to the pump, the heater core leaks. It got up to temp and never overheated. The top and bottom hoses where warm. We did discover that unlike a modern car with an overflow tank on this it is good to fill the radiator to the top, the overflow tube works. So with an unpressurized system like this how high should the radiator be filled? What is the proper way to get any air out of the system on this car? I am used to wait for the air to stop coming out the top but is this the same method for this one?
If your 41's radiator is the same as my 38's radiator, the overflow is well below the cap. Filling it to that will only guarantee loss of coolant as it expands. I fill my 38 to about an inch over the core.

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