RE: correct coolant system operation.

["ambradley@frontiernet.net" <ambradley@frontiernet.net>]

The radiator cap (1500/2000) or thermostat tower cap (1600) is not
pressurized and will always let air or water flow into the overflow
tank.  The overflow tank cap should be a pressurized cap that will only
let air/water out if the pressure exceeds its rating (should be 7lbs). 
Think of the overflow tank as part of the cooling system, not something
outside the cooling system.