Chevrolet 2003 Silverado 1500 Pickup Owner's Manual page 418

4. Then fill the coolant surge tank with the proper
mixture, to the FULL COLD mark.
5. 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 fan.
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 mark.
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