GMC SIERRA 1994 Manual page 228

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 surge tank is boiling, don't do anything else
until it cools down.
E
The coolant level
should be slightly
above the COLD
mark. If it isn't, you
may have a leak in the
radiator hoses, heater
hoses, radiator, water
pump or somewhere
else in the cooling
system.
5-20