Ok so today I finally finished doing headgaskets and fired my truck up, within a few minutes all the hoses felt stiff so I popped the radiator cap slowly and it shot out coolant, after putting it back on I let it idle a while longer and then coolant pushed out of the top of the lower radiator hose. I then shut the truck off and bleed it through the top hose and a lot of air came out, I then started the truck again with the cap off, no bubbles where vid able so I put it the cap on And everything was fine for about 10 minutes and then the hoses seemed pressurized again, so I bled it again but this time no air came out just water. Any ideas?