The resivour is there to maintain the radiator level during coolant expansion and retraction. When the coolant gets hot, it will expand and go into the overflow (therefore it you have it full to the top, it will have to leak out). And when the engine cools off, it wil return.
If you have other questions, let me know.
Joe
SPONSORED LINKS
Saturday, February 21st, 2009 AT 7:42 PM