Dodge dakota 2002 Service Manual page 1667

11 - 12 EXHAUST SYSTEM
TURBOCHARGER (Continued)
Fig. 15 Turbocharger Wastegate Actuator
1 - TURBOCHARGER
2 - DIAPHRAGM
3 - WASTE GATE ACTUATOR
• Improved operating economy
• Altitude compensation
• Noise reduction.
The turbocharger also uses a wastegate (Fig. 16),
which regulates intake manifold air pressure and
prevents over boosting at high engine speeds. When
the wastegate valve is closed, all of the exhaust gases
flow through the turbine wheel. As the intake mani-
fold pressure increases, the wastegate actuator opens
the valve, diverting some of the exhaust gases away
from the turbine wheel. This limits turbine shaft
speed and air output from the impeller.
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 bear-
ing housing, where it lubricates the shaft and bear-
ings (Fig. 17). 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
failure related to repeated hot shutdowns with inade-
quate "cool-down" periods. A sudden engine shut down
Fig. 16 Wastegate Operation
1 - SIGNAL LINE
2 - EXHAUST BYPASS VALVE
3 - WASTEGATE
4 - EXHAUST
5 - TURBINE
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 dam-
age the next time the vehicle is started.
Letting the engine idle after extended operation
allows the turbine housing to cool to normal operat-
ing temperature. The following chart should be used
as a guide in determining the amount of engine idle
time required to sufficiently cool down the turbo-
charger before shut down, depending upon the type
of driving and the amount of cargo.
DR