Chevrolet 2007 TrailBlazer Owner's Manua page 424

3. Fill the radiator with the proper DEX-COOL
coolant mixture, up to the base of the filler
neck. See Engine Coolant on page 414
for more information about the proper coolant
mixture.
424
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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.