[Michael C Henry]

The tank was Fords early attempt to eliminate air which causes foam in the coolant system while allowing for coolant expansion when hot. They have since gone to coolant recovery systems to make the coolant system a continous flow of liquid and and eliminate air. With the surge tank the air would just seperate from the liquuids flow at the coolant systems highest point. Points to remember are the head gasket coolant passages are blocked at the front . Coolant goes rearward in the block and forward in the head. The little hose between the intake manifold and coolant pump is your thermostat bypass . It will circulate coolant within the engine and pump. Once the thermostat opens the tank and radiator get involved. The modern thermostats with the small bleed hole are a great help. It lets a small quantity of fluid and air escape at the thermostat outward to the tank. This helps eminimate trapped air early in the filling proscess. I'm using a closed system cap (the one with a double seal ) intended for use with a coolant recovery system beyond the pressure cap on the surge tank. I have another colection botttle beyond the pessure cap at the surge tank to try allow for coolant expansion and keep the tank full of liquid to elminate any air that may cause foam. My bottle is actually a 1 qt. water bottle and holder intended for a bicycle. When the coolant in the system cools and contracts coolant is pulled back from the collection bottle keeping the rest of the coolant system full and preventing a colapse of the system hoses , tank and radiator due to vacume.