GMC Hybrid 2006 Owner's Manual page 39

2. Then keep turning the SGCM coolant surge tank
pressure cap slowly, and remove it.
3. Add the proper coolant mixture to the SGCM
coolant surge tank until the level reaches the
FULL COLD mark.
Notice: Using cooling system sealers or
conditioners in an attempt to stop coolant leaks
can damage the SGCM and engine cooling systems.
Never use cooling system sealers or conditioners
in your cooling system.
4. Then replace the
SGCM coolant surge
tank pressure cap.
Be sure the pressure
cap is hand-tight
and fully seated.
5-11