GMC 2010 Canyon Crew Cab Owner's Manual page 309

If coolant is needed, add the proper mixture directly to
the radiator, but be sure the cooling system is cool
before this is done.
1. Remove the radiator pressure cap when the
cooling system, including the 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.
2. Keep turning the cap to remove it.
3. Fill the radiator with the proper DEX-COOL
coolant mixture, up to the base of the filler
neck. See Engine Coolant on page 6-29 for more
information about the proper coolant mixture.
4. Fill the coolant recovery tank to the
FULL COLD mark.
5. Reinstall the cap on the coolant recovery tank,
but leave the radiator pressure cap off.
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