How To Add Coolant To The Radiator - GMC 2004 Envoy Owner's 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.
Turn the pressure cap slowly counterclockwise
about one full turn.
If you hear a hiss, wait for that to stop. A hiss
means there is still some pressure left.
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2. Then keep turning the pressure cap. Remove the
pressure cap.