GMC 2001 Envoy - Manual (Page 289)

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3. Fill the radiator with the proper DEX - COOL
R
coolant mixture, up to the base of the filler neck.
See “Engine Coolant” in the Index for more
information about the proper coolant mixture.
4. Then fill the coolant recovery tank to ADD mark.
5. Put the cap back on the coolant recovery tank,
but leave the radiator pressure cap off.