Originally Posted by WaltA
+1 Radiator cap.
IMHO, when you're doing any major work on the coolant system, it always pays to replace the cap with a good quality new one.
I 100% agree!! BUT I have had bad caps right out of the box, either too high of pressure or too low. You can't just trust the people in China put the right spring on the right cap. Test every cap. I always use NAPA parts and even there, I have had brand new items right of the box that didn't work as they are supposed to.
IMHO, there is NO WAY a new water pump can build up enough pressure to blow hoses off and blow top radiator tanks off. The cap would be the first thing I check.