prevent stress, leakage and body contact. If the sys-
tem contacts any body panel, it will transfer objec-
tionable noises originating from the engine to the
body.

When inspecting an exhaust system, critically

inspect for cracked or loose joints, stripped screw or

bolt threads, corrosion damage and worn, cracked or
broken hangers. Replace all components that are
badly corroded or damaged. DO NOT attempt to
repair.

When replacement is required, use original equip-

ment parts (or equivalent). This will assure proper
alignment and provide acceptable exhaust noise lev-
els.

CAUTION: Avoid application of rust prevention com-
pounds or undercoating materials to exhaust sys-
tem floor pan exhaust heat shields. Light overspray
near the edges is permitted. Application of coating
will result in excessive floor pan temperatures and
objectionable fumes.

SPECIFICATIONS - TORQUE

2.5L DIESEL - TORQUE SPECIFICATIONS

DESCRIPTION

N·m

Ft. Lbs.

In. Lbs.

Exhaust Manifold Nuts

32.4

—

Exhaust Manifold Heat

shield Bolts

27.5

—

Turbocharger Bracket

Bolts

47.1

—

Turbocharger Downpipe

Nuts

32.4

—

Turbocharger Oil Feed

Line Fitting

24.5

215

Turbocharger to Exhaust

Manifold Nuts

32.4

—

EXHAUST SYSTEM AND TURBOCHARGER

11 - 1

CHARGE AIR COOLER AND
PLUMBING

DESCRIPTION

The charge air cooler is located in front of the radi-

ator and cools the super heated air produced by the
compression of inlet air by the turbocharger. The
cooling of this super heated air maintains engine
power and efficiency (Fig. 1).

TURBOCHARGER

DESCRIPTION

CAUTION: The turbocharger is a performance part
and must not be tampered with. The wastegate
bracket is an integral part of the turbocharger. Tam-
pering with the wastegate components can reduce
durability by increasing cylinder pressure and ther-
mal loading due to incorrect inlet and exhaust man-
ifold pressure. Poor fuel economy and failure to
meet regulatory emissions laws may result. Increas-
ing the turbocharger boost WILL NOT increase
engine power.

The turbocharger is an exhaust-driven super-

charger which increases the pressure and density of
the air entering the engine. With the increase of air
entering the engine, more fuel can be injected into
the cylinders, which creates more power during com-
bustion.

The turbocharger assembly consists of four (4)

major component systems (Fig. 2) (Fig. 3):

• Turbine section

• Compressor section

• Bearing housing

• Wastegate

OPERATION

Exhaust gas pressure and energy drive the tur-

bine, which in turn drives a centrifugal compressor
that compresses the inlet air, and forces the air into
the engine through the charge air cooler and plumb-
ing. Since heat is a by-product of this compression,
the air must pass through a charge air cooler to cool
the incoming air and maintain power and efficiency.

Increasing air flow to the engine provides:
• Improved engine performance

• Lower exhaust smoke density

• Improved operating economy

• Altitude compensation

• Noise reduction.

Fig. 1 CHARGE AIR COOLER AND HOSES

1 - CHARGE AIR COOLER
2 - COOLING MODULE
3 - RADIATOR OUTLET HOSE
4 - CHARGE AIR COOLER TO TURBOCHARGER OUTLET HOSE
5 - RADIATOR INLET HOSE
6 - CHARGE AIR COOLER TO INTAKE MANIFLOD

Fig. 2 Turbocharger Operation

1 - TURBINE SECTION
2 - EXHAUST GAS
3 - BEARING HOUSING
4 - COMPRESSOR SECTION
5 - INLET AIR
6 - COMPRESSED AIR TO ENGINE
7 - EXHAUST GAS
8 - EXHAUST GAS TO EXHAUST PIPE

11 - 2

EXHAUST SYSTEM AND TURBOCHARGER

The turbocharger also uses a wastegate (Fig. 4),

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 block. The oil travels into the bearing hous-
ing, where it lubricates the shaft and bearings (Fig.
5). A return pipe at the bottom of the bearing hous-
ing, routes the engine oil back to the crankcase.

The most common turbocharger failure is bearing

failure related to repeated hot shutdowns with inad-
equate “cool-down” periods. A sudden engine shut
down after prolonged operation will result in the
transfer of heat from the turbine section of the tur-
bocharger 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 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.

Fig. 3 Turbocharger Wastegate Actuator

1 - TURBOCHARGER
2 - DIAPHRAGM
3 - WASTE GATE ACTUATOR

Fig. 4 Wastegate Operation

1 - SIGNAL LINE
2 - EXHAUST BYPASS VALVE
3 - WASTEGATE
4 - EXHAUST
5 - TURBINE
6 - EXHAUST BYPASS VALVE
7 - WASTEGATE
8 - EXHAUST
9 - TURBINE
10 - SIGNAL LINE

EXHAUST SYSTEM AND TURBOCHARGER

11 - 3

TURBOCHARGER (Continued)

TURBOCHARGER

(

COOL DOWN

(

CHART

Driving

Load

Turbo-

charger

Idle Time

(in minutes)

Condition

Tempera-

ture

Before Shut

Down

Stop & Go

Empty

Cool

Less than 1

Stop & Go

Medium

Warm

Highway

Speeds

Medium

Warm

City Traffic

Max.

GCWR

Warm

Highway

Speeds

Max.

GCWR

Warm

Uphill

Grade

Max.

GCWR

Hot

CLEANING

All old gaskets should be inspected for any tears or

signs of prior leakage. If any gaskets show such indi-
cations, they should be replaced with new gaskets.
All gasket mating surfaces must be cleaned of old
gasket material to produce a smooth and dirt free
sealing surface for the new gasket.

INSPECTION

Visually inspect the turbocharger and exhaust

manifold gasket surfaces. Replace stripped or eroded
mounting studs.

(1) Visually inspect the turbocharger for cracks.

The following cracks are NOT acceptable:

• Cracks in the turbine and compressor housing

that go completely through.

• Cracks in the mounting flange that are longer

than 15 mm (0.6 in.).

• Cracks in the mounting flange that intersect

bolt through-holes.

• Two (2) Cracks in the mounting flange that are

closer than 6.4 mm (0.25 in.) together.

(2) Visually inspect the impeller and compressor

wheel fins for nicks, cracks, or chips. Note: Some
impellers may have a factory placed paint mark
which, after normal operation, appears to be a crack.
Remove this mark with a suitable solvent to verify
that it is not a crack.

(3) Visually inspect the turbocharger compressor

housing for an impeller rubbing condition (Fig. 6).
Replace the turbocharger if the condition exists.

(4) Measure the turbocharger axial end play:

(a) Install a dial indicator as shown in (Fig. 7).

Zero the indicator at one end of travel.

(b) Move the impeller shaft fore and aft and

record the measurement. Allowable end play is
0.038 mm (0.0015 in.) MIN. and 0.089 mm (0.0035
in.) MAX. If the recorded measurement falls out-
side these parameters, replace the turbocharger
assembly.
(5) Measure the turbocharger bearing radial clear-

ance:

(a) Insert a narrow blade or wire style feeler

gauge between the compressor wheel and the hous-
ing (Fig. 8).

(b) Gently push the compresser wheel toward

the housing and record the clearance.

gently push the compressor wheel away from the
housing and again record the clearance.

(d) Subtract the smaller clearance from the

larger clearance. This is the radial bearing clear-
ance.

(e) Allowable radial bearing clearance is 0.326

mm (0.0128 in.) MIN. and 0.496 mm (0.0195 in.)
MAX. If the recorded measurement falls outside
these specifications, replace the turbocharger assy.

Fig. 5 Turbocharger Oil Supply and Drain

1 - BEARINGS
2 - OIL SUPPLY (FROM ENGINE BLOCK)
3 - OIL RETURN (TO OIL PAN)

11 - 4

EXHAUST SYSTEM AND TURBOCHARGER

TURBOCHARGER (Continued)

Content .. 1101 1102 1103 1104 ..