Hello all long time member ,not been on for a while

I have a 2006 4.2 ti
Every time I tow the campervan it boils when towing up steep hills,
It runs 16pound boost ..
Never does it any other time never runs hot any other time
Even when off rd it doesn't get hot .
Is the turbo water cooled or what is causing this problem of over heating it only made it half way up Cunningham's gap qld yesterday after noon before the water watchdog alarm was screaming its titts off ,getting over patrols really quick

Can any one please give me some help


Would draining all coolant from engine and intercooler and replacing help

Cheers neil