GMC 2003 Sierra - Manual (Page 417)

A CAUTION:
Adding only plafn water to your coding
syfitem can iK dangerous. Plain water, or
some other liquid such as alcohol, can boil
before the proper coolant mixture wllL Your
vehicle’s coolant warning system is set for
theproper coolant mintureH V/ith plain water or
tdfl wrong mixture, your engine could get too
hot but you wouldn't get the overheat warning.
Your engine could catch tire and you or others
couEd be burned. Use a mixture of deán,
drinkable water and a proper coolant.
Notice: In coid weather, water can freeze and crack
the engine, radiator, heater core and other parts.
Use the recommended coolant and the proper
coolant mixturc-
Vou can be burned if you spill coolant on hot
engihE parts. Coolant contains ethylene glycoE
and i1 will burn tf the engine parts arc hot
enough. Don't spill coolant on a hot engine.
1. Park the vEhfde on a
levef surface. You can
remove the coolant
surge lank pressure
cap when the cooling
system, including
the coolant surge lank
pressure cap and
upper radiator hose, ts
no longer holr
2. Turn the pressure cap sJowty counterclockwise (left)
about one fuN lum. if you hear a hiss, wait for thal to
stop. A hiss means there is still some pressure left
3. Then keep turning the pressure cap slowly, and
remove il.
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