Cadillac 2003 CTS Owner's Manual page 312

3. Then fill the coolant surge tank with the proper
mixture, to slightly above the FULL COLD/FROID
line on the side of the coolant surge tank.
4. With the coolant surge tank pressure cap off, start the
engine and let it run until you can feel the upper
radiator hose getting hot. Watch out for the engine
cooling fans.
By this time, the coolant level inside the coolant
surge tank may be lower. If the level is lower, add
more of the proper mixture to the coolant surge tank
until the level reaches the FULL COLD/FROID line
on the side of the coolant surge tank.
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