Chevrolet sonic 2016 Owner's Manual page 236

Caution
In cold weather, water can freeze
and crack the engine, radiator,
heater core, and other parts. Use
the recommended coolant and
the proper coolant mixture.
Warning
You can be burned if you spill
coolant on hot engine parts.
Coolant contains ethylene glycol
and it will burn if the engine parts
are hot enough. Do not spill
coolant on a hot engine.
1.4L Engine Shown, 1.8L Engine
Similar
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
counterclockwise about
one-quarter of a turn. If you
hear a hiss, wait for that to
stop. This will allow any
pressure still left to be vented
out the discharge hose.
2. Keep turning the pressure cap
slowly and remove it.
Vehicle Care
3. Fill the coolant surge tank with
the proper DEX-COOL coolant
mixture to the indicated
level mark.
4. With the coolant surge tank
pressure cap off, start the
engine and let it run until you
can feel the upper radiator
hose getting hot. Watch out for
the engine cooling fan.
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