Do both radiator hoses get hard or one hard and the other collapse?

 

 

Blown head gasket.

 

I agree with you HeyYou. The only other thing would be if they were used heads that were the replacement part and they didn't get Magna fluxed to check for cracks. It definitely sounds like engine pressure blowing into the cooling system.

 

 

Is there ANY chance you could of buggered up one of the head gaskets when putting them in? I have done that before but I admit it is rare to do it.

 

 

The ONLY way the cooling system can develop that much pressure, that fast, is if cylinder pressure is finding its way in there. There is no other method I know of that makes the hoses get that hard, that fast.

 

Jack the front of the vehicle off the ground 8 inches or so when filling the radiator with coolant. This will help any air in the system find its way out. Once its full and the truck is back on LEVEL ground have someone start the engine while you watch the radiator opening for bubbling (radiator cap off). If your hoses are pumping up as fast as you say there must be a good amount of bubbles in the coolant. If you see bubbles you know the head gasket is not sealing or a cracked block. Doing the comp test will help you know which cylinder to look at when taking it back apart.

Also, the hoses are new and soft when the engine is off correct? New thermostat too?

Did the engine ever get too hot where the block could have warped and the heads wont seal now?

Just spit balling possibilities...
Good luck!