GMC Hybrid 2007 Owner's Manual page 45

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.
45