Pete, be aware that the thermostatically controlled valve, part #18502, has a rubber seal that is probably cracked and leaking if still original. I have the same heater system in my '49 F-2, and just two weeks ago, I went out to find that the passenger floor board had coolant on it. I was able to "rebuild" the valve a couple days later with a new seal.

If you have overhauled that valve, now is the time to do it. NAPA has a "kit" that contains a new seal, plus instructions on how to install the part.

If you want, I can get you the Balkamp part number.

J.D.