ok when the truck is warm it starts pissing coolant, shut it off it stops. Nasty hissing noise. Disconnected the upper radiator hose, no cracks or leaks,same with the lower. But when it is connected and you squeeze eitther hose you can hear hissing.
What can it be????

Either a water pump or what??

 

It leaks under pressure. get a pressure tester andd that will show you where it is leaking from. Prolly the water pump.