Gpw zero radiator cap

[c1959palmer]

I have recently got my hands on a NOS overflow tank for my 45 gpw. Now what I need is the zero radiator cap. Does anyone know where I can buy one or somehow modify a 7 lbs to a 0 lbs?

[Michael O.]

Aren't they the same as the fuel sump drain caps?

[artificer]

Yes...

[Wolfman]

OK. Enlighten me. I realize we are dealing with 1940s technology.
My understanding of an over flow system is by adding the over flow tank, the radiator is completely filled.
A pressure cap is still used but the over flow tube is now connected to the tank so the expanding coolant that would run out on the ground goes to the tank. The cap still keeps pressure on the cooling system.
When the system cools, a check valve in the cap opens to allow coolant in the over flow tank to be drawn back into the radiator.
So, this is not the case in 194x and the over flow system was not pressurized ??

[c1959palmer]

From what I have read trying to figure how to mount this is that I need a zero cap on my radiator and a pressure cap on the expansion tank so that there is no restriction for the coolant to go back into the radiator... looks like I'll be getting a fuel tank sump cap and give it a try.

[Chuck Lutz]

The kit comes with a sealing cap which will allow coolant to escape into the overflow tube which is now attached to the external surge tank. That tank has a pressurized cap on it (4 lbs) which allow for the EXPANSION of coolant to move from the radiator into the surge tank and for the escape of air pressure over 4 lbs to exit the system via the cap.

In this manner the coolant will expand into the surge tank rather than into the dirt below the jeep and when the jeep cools down and the coolant contracts, it is sucked BACK through the hose & overflow tube into the radiator. By closing off the neck of the radiator filler but keeping the overflow tube free, this can occur.

The "kit" comes with a cap, A 6942, which is placed on the radiator and the existing radiator cap, A 1215 is moved to the surge tank.

Surge Tank Instructions.jpg (69.37 KiB) Viewed 397 times

The gas tank well cap is A 3055.

That would indicate to me that while the tank well cap may FIT onto the radiator with the surge tank installed, it isn't the same item or it would have the same part number, right? Not to say it won't work but has anyone pressure tested a working radiator with one on it to see if it a) holds pressure in excess of 4 lbs and b) allows the expansion of coolant to the surge tank via the over flow tube?

[Wolfman]

That explains it. 6 of one. Half a dozen of the other. Or, there is more than one way to skin a cat.
My concern was with, pressurizing the cooling system.
Moving the pressure cap to the surge tank with a straight cap on the radiator does the trick.
As far as the sump cap fitting the radiator ??? If you say so. Never tried it.
Try it and see what happens.