GMC 1999 Sierra 1500 Pickup Owner's Manual page 253

Cooling
System
PO21 0
When you decide it's safe to lift the hood, here's what you'll see:
A. Coolant recovery tank
B. Radiator pressure cap
C. Engine fan
CAUTION
' 4 An electric fan under the hood can start up even when the engine is
not running and can injure you. Keep hands, clothing, and tools
away from any electric fan.
m
If the coolant inside the coolant recovery tank is boiling, don't do anything
else until it cools down.
5-1 1