GMC Hybrid 2007 Owner's Manual page 44

CAUTION:
{
You can be burned if you spill coolant on
hot engine parts. Coolant contains
ethylene glycol and it will burn if the
engine parts are hot enough. Do not spill
coolant on a hot engine.
If the SGCM coolant is more than one inch
(2.54 cm) below the FULL COLD mark, your
vehicle must be serviced by your dealer and a
special fill procedure must be followed.
Notice: Attempting to fill the hybrid cooling
surge tank yourself when the fluid level is more
than 1 inch (2.54 cm) below the FULL COLD
mark can damage your vehicle. Your vehicle
must be serviced.
44
1. Park the vehicle on a level surface and turn
the vehicle off. You can remove the SGCM
coolant surge tank pressure cap when
the SGCM cooling system, including the
SGCM coolant surge tank pressure cap and
SGCM cooling hoses, are no longer hot.
Turn the SGCM coolant surge tank pressure
cap slowly counterclockwise (left) about
one full turn. Wait 30 seconds.