[FrankieT/A]

If you're gonna run a recovery tank you will need to use a late model cap. Because: the early caps when cars had no recovery system used one gasket at the bottom of the relief valve. In the old days the fluid got hot, expanded and belched out coolant and it went to the atmosphere. However, in a recovery system the cap has two gaskets,one at the original location plus at the top (at the mouth of the radiator) 'cause as the coolant cools it creates a vacuum (due to contraction) thusly drawing coolant from the tank. (the hose from the radiator must enter the tank from the bottom or have a straw type hose if you will from the cap because obviously the hose must be submerged in coolant to create the syphon back to the rad). Lev-R-Vent type caps do not work on coolant recovery systems. Anyone who has canned meat or vegetables knows you put the product in the jar "Hot", when it cools and you open the lid you hear the air rush in. As the jar cools, the stuff inside contracts and creates the low pressure. Voila! Vacuum packed.

Hope this helps!