Chevrolet 2009 TrailBlazer Owner's Manual page 339

3. Fill the radiator with the proper DEX-COOL coolant
mixture, up to the base of the filler neck. See Engine
Coolant on page 5-29 for more information about the
proper coolant mixture.
4. Then fill the coolant recovery tank to the
FULL COLD mark.
5. Put the cap back on the coolant recovery tank,
but leave the radiator pressure cap off.
5-33