upper rad hose stay hard even after sitting overnight
 

i just bought a 2001 chevy 2500HD with a 6.6 durmax diesel i do have back round in auto GAS that is none in DIESEL im still looking for the Sparkplugs but what i got is a truck the bubbles in the over flow tank and i was thinking headgaskets then today i took a look at it and still now sparkplugs so i found a hose that gos to the turbo to the coolant hose dead center of the intake and when i pinch it it stops bubbling in the overflow tank i have changed the overflow cap and put new thermostat and still having the problem any help i hear there is a o ring in the turbo for the coolant that goes bad or im i just hoping its not the headgaskets i talked to ashop and they said 4800.00 to replace them ?
upper rad hose stay hard even after sitting overnight sorry forgot this too
the truck has never overheated

There is a hose connected to the top radiator hose outlet which leads back to the turbo. I am assuming that it carries coolant to cool the turbine side. Is it possible that I have some boost leaking past something in the turbo charger and getting into the cooling system there? Any ideas on this theory?

2500HeavyDuty i bleed the air ou of the system at the thermostat housing the olny way it stops bubbling is if i bock off the hose that comes off the thermostat housing whitch i was told was a bypass valveim not even sure what its bypassing too it looks to be going to the turbo im thinkig headgaskest to rich s imjust tryingto understand why when i pinch that small hose it quits building presser