Buick LaCrosse 2012 Owner's Manual page 344

10-18 Vehicle Care
The coolant surge tank pressure
cap can be removed when the
cooling system, including the surge
tank pressure cap and upper
radiator hose, is no longer hot.
1. Turn the pressure cap slowly
counterclockwise. If a hiss is
heard, wait for that to stop.
A hiss means there is still
some pressure left.
2. Keep turning the cap and
remove it.
3. Fill the coolant surge tank with
the proper mixture to the mark
pointed to on the front of the
coolant surge tank.
I n f o r ma t i o n P r o v i d e d b y :
4. With the coolant surge tank cap
off, start the engine and let it run
until the upper radiator hose
starts 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 the mark pointed to on
the front of the coolant
surge tank.
5. Replace the cap. Be sure the
cap is hand tight and fully
seated.
Notice: If the pressure cap is not
tightly installed, coolant loss and
possible engine damage may
occur. Be sure the cap is properly
and tightly secured.