So I don't know what you mean "leaking out around the cap" but a 4 lb cap will allow coolant to come out when the pressure exceeds 4 lbs. You also need some space in the top of the tank for expansion.


1951 GMC 1 Ton Flatbed -- It is finally on the road and what a great time I have driving it!
1951 1 Ton Completed


My Chevy Master 4 Door is on the Road!