Buick 2009 Lucerne Owner's Manual page 314

CAUTION:
{
An electric engine cooling fan under the hood can
start up even when the engine is not running and
can cause injury. Keep hands, clothing, and tools
away from any underhood electric fan.
CAUTION:
{
Steam and scalding liquids from a hot cooling
system can blow out and burn you badly. They are
under pressure, and if you turn the surge tank
pressure cap — even a little — they can come out
at high speed. Never turn the cap when the cooling
system, including the surge tank pressure cap, is
hot. Wait for the cooling system and surge tank
pressure cap to cool if you ever have to turn the
pressure cap.
5-30
1. Turn the pressure cap slowly counterclockwise.
If you hear a hiss, wait for that to stop. A hiss
means there is still some pressure left.
2. Then keep turning the cap and remove it.
You can 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.
3. Fill the coolant
surge tank with the
proper mixture to the
FULL COLD mark on
the side of the coolant
surge tank.