GMC 2004 Savana - Manual (Page 271)

Radiator Pressure Cap The radiator pressure cap is located near the center of
the engine compartment. See Engine Compartment
Overview on page 5-12 for more information on location.
Notice: If the pressure cap is not tightly installed,
coolant loss and possible engine damage may
occur. Be sure the cap is properly and tightly
secured.
Engine Overheating
You will find a coolant temperature gage on your
vehicle’s instrument panel.
5-25