Cadillac ATS 2018 Owner's Manual page 269

Warning
Steam and scalding liquids from a
hot cooling system are under
pressure. Turning the pressure cap,
even a little, can cause them to
come out at high speed and you
could be burned. Never turn the cap
when the cooling system, including
the pressure cap, is hot. Wait for
the cooling system and pressure
cap to cool.
Caution
Failure to follow the specific
coolant fill procedure could cause
the engine to overheat and could
cause system damage. If coolant is
not visible in the surge tank,
contact your dealer.
If no problem is found, check to see if
coolant is visible in the coolant surge
tank. If coolant is visible but the
coolant level is not at the bottom of
the fill neck, add a 50/50 mixture of
clean, drinkable water and DEX-COOL
coolant at the coolant surge tank, but
be sure the cooling system, including
the coolant surge tank pressure cap, is
cool before you do it.
1. Remove the coolant surge tank
pressure cap from the top
chamber when the cooling
system, including the coolant
surge tank pressure cap and
upper radiator hose, is no
longer hot.
Turn the pressure cap slowly
counterclockwise. If you hear a
hiss, wait for that to stop. This
will allow any pressure still left
to be vented out the
discharge hose.
2. Keep turning the pressure cap
slowly and remove it. Open the
surge tank service port cap to
the lower chamber
VEHICLE CARE
3. Fill the surge tank top chamber
with the proper mixture to the
bottom of the fill neck. The top
chamber needs to be completely
full. Fill the surge tank bottom
chamber through the service port
to approximately half.
4. With the coolant surge tank
pressure cap off and the surge
tank service port cap open, 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 top
chamber may be lower. If the
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