Cadillac 2008 CTS - Manual (Page 319)

3. Fill the coolant surge tank with the proper mixture,
to slightly above the FROID/FULL COLD 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. The upper radiator
hose is the top hose coming out of the radiator, on
the passenger’s side of the vehicle. 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 FROID/FULL COLD
line on the side of the coolant surge tank.
5. Then replace the pressure cap. Be sure the
pressure cap is hand-tight and fully seated.
Recheck the coolant level in the bottle next time you
use your vehicle to insure the system is full when cold.
See Engine Coolant on page 5-27.
5-37