Overflow tank helps to keep your precious coolant in your radiator. Here’s how to use it.
Cursing, the driver shifted to a still lower gear. Those blistering, shifting sands were tougher to fight than the Nazis. He glanced at the heat indicator. It looked bad.
Realizing how little of his reserve water supply was left, he stopped the truck to cool it. He climbed down from the cab. Then it happened…first a rumbling, gurgling noise followed by water gushing out the overflow pipe. He looked under the truck just in time to see the irreplaceable liquid disappear into the parched sand…O.K.–you can relax now; it’s only a yarn. But for you fellows whose vehicles don’t have them, that’s why radiator overflow tanks have been installed on half-tracks, scout cars, and some Dodges, and (in the future) on GMC’s and 1/4-ton jeeps. Not all the Dodges, GMC’s and 1/4-tons are to be modified, but more on this later. After reading the Desert Cooling System Kit modification work orders for these vehicles, we couldn’t see why any mechanic should have trouble making the modification. In each case it means changing the fan assembly, radiator cap and fan belt, and installing an overflow tank which is hooked up to the radiator overflow pipe. On the Willys and Ford 1/4-tons the modification also requires installing a larger radiator core.
As anyone who has driven in hot climes knows, when coolant gets hot it expands. And if no place is provided to receive the expanded coolant – it will flow out the overflow pipe to the ground. If this happens in an area with a scarcity of water, somebody is going to be mighty thirsty. But on vehicles equipped with the overflow tank, this doesn’t happen. The cooling system is sealed by a positive seal cap on the radiator and by tubing running from the radiator overflow pipe to the overflow tank. The tank has a pressure cap.
When the coolant expands from heat, the water that would ordinarily run out the overflow pipe is conducted into the overflow tank. When the temperature of the coolant in the radiator decreases it forms a partial vacuum in the line between the radiator and overflow tank. This partial vacuum causes the coolant in the tank to flow back into the cooling system – if you have kept the cooling system good and tight.
Any air leaks in the cooling system, such as loose hose connections or a vented radiator cap, will break the vacuum and prevent the coolant in the tank from returning. If the coolant level in the radiator is found low, the overflow tank should be checked for trapped liquid before any additional water is added. If there is water in the tank, it should be drained into a container by using the valve and poured back into the radiator. But the presence of coolant in the tank after the radiator has cooled, is a sure indication that the system isn’t working right. In such cases, check for proper installation of the kit, check all hose connections for leaks, and check the radiator cap to make sure some one didn’t slip you a vented one. (A vented one will break the vacuum in the radiator to overflow line). But if the water in the radiator is low and isn’t in the overflow tank, you can start looking over your cooling system for a water leak.
Now if you follow these few simple rules your desert cooling system kit will work O. K.
‘Where and when do I requisition the desert cooling system kits for the GMC’s, 1/4 ton jeeps and 3/4-ton Dodges?’ The answer is you don’t requisition them. They will requisition you. When your destiny is decided — that is, when it is known you are going to a water-short area, you will be given the desert cooling system kits.
You can find out more interesting facts about WW2 jeeps and maintenance in my book: Military Maintenance for MB/GPW Jeeps 1941-45.