How To Add Coolant To The Radiator - GMC SIERRA 1997 Manual

How to Add Coolant to the Radiator
1. You can remove the radiator pressure cap when
the cooling system, including the radiator pressure
cap and upper radiator hose, is no longer hot. T u r n
the pressure cap slowly counterclockwise until it
first stops. (Don't press down while turning the
pressure cap.)
2. Then keep turning the pressure cap, but now push
down as you turn it. Remove the pressure cap.
If you hear a hiss, wait for that to stop. A hiss means
there is still some pressure left.