GMC 1996 Sierra Owner's Manual page 228

Cooling System
--
Gasoline Engines
When you decide it's safe t o lift the hood, here's what
you'll see:
A. Coolant Recovery Tdnk
B. Radiator Pressure Cap
C. Engine Fan(s)
A
CAUTION:
If your vehicle has air conditioning, the auxiliary
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 underhood electric fan.
If the coolant inside the coolant recovery tank is boiling,
don't do anything else until
it
cools down.