Paccar Peterbilt 567 2021, Manual

Page: 135 / 332

Engine, Under Hood Air Intake
This switch opens a door in the engine air
filter housing so that the air is taken from
under the hood instead of outside air. This
switch can be useful when starting the
vehicle in cold weather conditions.
CAUTION
Only operate the under hood intake air
switch when outside temperatures are
below 32°F (0°C). Engaging the under
hood air intake while temperatures are
above freezing may result in engine
damage.
Engine Warm Up
Engine warm-up allows oil film to be
established between pistons and liners,
shafts and bearings while your engine
gradually reaches operating temperature.
1. After you’ve started your engine,
idle it at approximately 600 rpm
while you check:
• Oil pressure
• Air pressure
• Alternator output
2. After a few minutes of idling at 600
rpm, increase your idle speed to
900 or 1,000 rpm. Continue your
warm-up. This procedure allows oil
to warm and flow freely while
pistons, liners, shafts, and bearings
expand slowly and evenly. In
extremely cold temperatures, you
may have to increase idle speed.
NOTE
In colder climates where the tempera-
ture is often below freezing, the warm-
up for turbocharged engines is espe-
cially important. Chilled external oil
lines leading to the turbocharger will
slow the oil flow until the oil warms, re-
ducing oil available for the bearings.
Watch the engine oil temperature or
pressure gauge for a warming trend
before increasing engine idle speed
(rpm).
3. Continue the engine warm-up until
the coolant temperature reaches at
least 130°F (54°C). At this
temperature, you can use partial
throttle. Wait until the coolant
temperature is at least 160°F
(71°C) before operating at full
throttle.
NOTE
Under most circumstances, idling your
engine for long periods merely wastes
fuel. In severe arctic weather condi-
tions, however, you may need longer
idling to be sure all parts of your en-
gine are fully lubricated.
DRIVING - Starting and Warming Up
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