Chevrolet Low Cab Forward 4500 2019 Series Owner's Manual page 264

External Engine Cleaning
The engine does not need periodic
cleaning, nor is it recommended.
If you insist on cleaning the engine,
clean it only when it is cold, never
when it is warm or hot, and never
when the engine is running.
Spraying or pouring water or other
fluids on your engine when it is
warm or hot, or when it is running,
can cause serious damage to the
engine and its components,
particularly the fuel supply pump.
Handling the Radiator
Cleaning the Radiator Core
Vehicle Care
Cooling efficiency is compromised
when there is dirt or dust plugging
air passages in the radiator core (1).
This can also cause corrosion of the
cores (3). Wash the radiator core
with tap water every 24 months.
Make sure to turn the engine off and
remove the key from the ignition
before cleaning the cores.
The engine, exhaust pipe, and
radiator will be hot immediately after
the vehicle is driven. Be careful
around these parts to prevent burns.
Clean the engine when it is cold.
Do not clean the radiator or
surrounding areas using water that
is supplied under high pressure.
Doing so may cause damage.
When cleaning the radiator core, do
not crush or damage the fins. The
fins are very fragile so be careful not
to bend them out of shape. If they
become deformed, their cooling
efficiency will be impaired. Before
cleaning, ensure that no water will
splash onto the surrounding
electrical components and wires.
If stubborn dirt still remains even
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