Cadillac 2004 DeVille - Manual (Page 317)

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 about 4.5 inches (11.4 cm)
from the top of the filler neck.
5. Then replace the pressure cap. Be sure the arrow
on the pressure cap lines up like this.
Start the engine and allow it to warm up. If the CHECK
COOLANT LEVEL message does not appear on the
Driver Information Center, coolant is at the proper
fill level. If a CHECK COOLANT LEVEL message does
appear, repeat Steps 1 to 3 and reinstall the pressure
cap or see your dealer.
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