I am yet to buy a radiator overflow tank. i am looking at some and i see that some say recovery can. how does it put the coolant back into the radiator? also is anyone using a recovery can or just a overflow tank?
The radiator cap has an inner spring and seat that allows the expanding coolant to flow out into the can. As the coolant in the radiator cools and contracts, it causes a siphon action to bring the coolant back in from the can.
Some cans have the overflow hose hook up to the bottom and some have the hose routed to the top with an inner hose/tube that will siphon the coolant back into the radiator. Both should have some kind of vent to allow air in and out, which could be as simple as a hole in the cap.
Some of the fancy ones hace a valve on the bottom to drain.