Reply to "Expansion tank cap"

Larry is correct. Back in the day, some people advocated running pressure caps on both tanks, or interchanging the large overflow tank cap with the pressure-relief cap on the small surge tank, thinking this would allow more water to circulate in the cooling system. It doessn't, but usually does no harm, either. Biggest problem is the extended length of stock tank necks on both tanks, and the very rough bottom of the necks where the cap is supposed to seal. Both allow a 14-lb cap to open at maybe 8 lbs so you never get the benefits of the advertised pressure. Worse, the caps leak, and the design of most Panteras allows the leaking water to run down the inner fender panel and straight into the right frame opening, where it rusts your suspension from the inside.