GMC 2008 Acadia - Manual (Page 345)

3. Keep turning the
pressure cap slowly,
and remove it.
4. Fill the radiator with the proper DEX-COOL ®
coolant mixture, up to the base of the filler
neck. See Engine Coolant on page 5-22 for more
information about the proper coolant mixture.
5. Fill the coolant recovery tank to the FULL
COLD mark.
6. Reinstall the cap on the coolant recovery tank, but
leave the radiator pressure cap off.
5-31