Correction: he says it doesn't hunt wildly until the engine gets hot.
It is also overheating within about 15 min at idle, but engine fan is
running. He recently had the radiator checked and reinstalled it. The
first day after reinstalling it, the car ran fine, so it is nothing to
do with the way he installed the radiator.  The upper hose gets hot
within a minute or so of start-up.  I told him to remove the
thermostat...he did but there it still iverheated quickly. He says
when it overheats, he loses colant out the (new) reservoir tank.  It
must be lsing out the pressure relief on the cap, he says there are no
apparent leaks on the reservoir. It just builds up tremendous pressure
when the car overheats.  
  The day before he repaired the turbo, I checked the engine temp
with a digital IR thermometer gun, and at the thermostat housing, the
temp was regulating (by the fan turning on/off) at about 210 Deg at
idle. He says he doesn't see how they accidently dosconnected any
sensor.  
  How else can we flow-check the coolant other than the upper-hose
heat check?