GMC CHEVROLET Silverado 6500HD 2019 Owner's Manual page 305

304 Vehicle Care
Warning
Spilling coolant on hot engine
parts can burn you. Coolant
contains ethylene glycol and it will
burn if the engine parts are hot
enough.
Warning
Steam and scalding liquids from a
hot cooling system are under
pressure. Turning the pressure
cap, even a little, can cause them
to come out at high speed and
you could be burned. Never turn
the cap when the cooling system,
including the pressure cap, is hot.
Wait for the cooling system and
pressure cap to cool.
Caution
Failure to follow the specific
coolant fill procedure could cause
the engine to overheat and could
cause system damage. If coolant
is not visible in the surge tank,
contact your dealer.
If no coolant is visible in the surge
tank, add coolant as follows:
1. 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.
Turn the pressure cap slowly
clockwise about one-half turn.
If a hiss is heard, wait for that
to stop. A hiss means there is
still some pressure left.
2. Keep turning the pressure cap
slowly, and remove it.
3. Slowly fill the coolant surge
tank. Do not let the coolant
level go above the indicated
mark in the tank until after the
engine comes to the operating
temperature in Step 4.
4. With the coolant surge tank
pressure cap off, start the
engine and let it run until the