Buick 2013 Verano Owner's Manual page 264

You can be burned if you spill
coolant on hot engine parts.
Coolant contains ethylene glycol
and it will burn if the engine parts
are hot enough. Do not spill
coolant on a hot engine.
1. Remove the coolant surge tank
pressure cap 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 about
one-quarter of a turn. 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.
3. Fill the coolant surge tank with
the proper DEX-COOL coolant
mixture to the indicated
level mark.
4. With the coolant surge tank
pressure cap off, start the
engine and let it run until the
upper radiator hose can be felt
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
DEX-COOL coolant mixture to
the coolant surge tank until the
level reaches the indicated
level mark.
5. Replace the pressure cap. Be
sure the pressure cap is
hand-tight.
Check the level in the coolant surge
tank when the cooling system has
cooled down. If the coolant is not at
the proper level, repeat Steps 1
through 3 and reinstall the pressure
cap. If the coolant still is not at the
proper level when the system cools
down again, see your dealer.