[vtmecheng]

That makes no sense at all if he is getting air into the cooling system. The system is designed to not have air in it, liquid only. If air is sucked in then the air is displacing the coolant, air comes in causing coolant to stay in the overflow tank. I can understand adding fluid if you go from a bad cap to a good one because your engine will be able to suck up coolant from the overflow instead of air from the atmosphere, requiring more coolant. As said before, if air is in the system it will take up space normally filled with coolant.