The turbocharger is lubricated by engine oil that is
pressurized, cooled, and filtered. The oil is delivered to
the turbocharger by a supply line that is tapped into
the oil filter head. The oil travels into the bearing hous-
ing, where it lubricates the shaft and bearings. A
return pipe at the bottom of the bearing housing,
routes the engine oil back to the crankcase.
The most common turbocharger failure is bearing fail-
ure related to repeated hot shutdowns with inadequate
“cool-down” periods. A sudden engine shut down after
prolonged operation will result in the transfer of heat
from the turbine section of the turbocharger to the
bearing housing. This causes the oil to overheat and
break down, which causes bearing and shaft damage
the next time the vehicle is started.
Letting the engine idle after extended operation allows
the turbine housing to cool to normal operating tem-
perature. The following chart should be used as a
guide in determining the amount of engine idle time required to sufficiently cool down the turbocharger before shut
down, depending upon the type of driving and the amount of cargo.
TURBOCHARGER “COOL DOWN” CHART
Driving Condition
Load
Turbocharger
Temperature
Idle Time (in minutes) Before
Shut Down
Stop & Go
Empty
Cool
Less than 1
Stop & Go
Medium
Warm
1
Highway Speeds
Medium
Warm
2
City Traffic
Max. GCWR
Warm
3
Highway Speeds
Max. GCWR
Warm
4
Uphill Grade
Max. GCWR
Hot
5
11 - 26
EXHAUST SYSTEM
DR/DH