Chapter
C
: Fuel, Air Induction, and Exhaust Systems Diagnosis and Repair
70
Turbocharger Inspection
Perform a preliminary inspection as follows:
1. Make sure the air cleaner is in place and that there
are no loose connections, leaks, restrictions, or
broken ductwork.
2. Check the exhaust system for burned areas, leak-
age, and loose connections.
3. Disconnect the turbocharger air inlet and exhaust
outlet, then inspect the turbine and compressor
with a flashlight and a mirror. Look for bent or bro-
ken blades and wear marks on the blades or hous-
ing.
4. Turn the turbine wheel by hand. Listen and feel for
binding or rubbing. Check for free play by moving
both ends of the shaft up and down. There should
be little if any movement.
5. Check the shaft seal areas for signs of oil leakage,
figure 3-30.
Turbocharger Service
Turbocharger service consists of testing the boost pres-
sure and checking the wastegate operation. A tur-
bocharger can be disassembled, internal components
replaced, and clearances set with a dial indicator. How-
ever, common practice is to simply replace a defective
unit.
Testing Boost Pressure
Boost pressure can be checked during a road test, or on
a chassis dynamometer, using a pressure gauge. Con-
nect the gauge to a pressure port on the compressor
side of the turbo, or tee it into the line running to the
warning lamp pressure switch. Use a long enough hose
so the gauge is inside the passenger compartment dur-
ing testing. A turbocharger will not develop normal
boost unless the engine is under load. Start and warm
the engine to normal operating temperature. Accelerate
from zero to 40 or 50 mph and note the gauge reading
under load. Compare results to Service Manual specifi-
cations.
Testing the Wastegate Actuator
The wastegate is a pressure relief device that protects
LACK OF POWER OR
EMITS BLACK EXHAUST SMOKE
POSSIBLE CAUSE
CORRECTION
Damaged or disconnected
air cleaner ducting
Restricted air filter element
Intake or exhaust manifold leak
Turbocharger damage
Exhaust system restriction
Carburetor or fuel injection
problem
Incorrect ignition timing,
advance–or other ignition
problem
EGR problem
Lack of compression or other
engine wear
Low boost pressure
Inspect and correct
Replace air filter
Check turbocharger installation
for air or exhaust leak
Check turbocharger rotating
assembly for binding or
dragging
Check exhaust system; check
manifold heat control valve
Inspect and correct
Inspect and correct
Inspect and correct
Inspect and correct
Check boost pressure and
wastegate operation; adjust
or replace as required
Fig. 3-27.
Turbocharger diagnosis lack of power or black exhaust
smoke.
HIGH OIL CONSUMPTION
OR EMITS BLUE EXHAUST SMOKE
POSSIBLE CAUSE
CORRECTION
Excessive blowby or PCV
problem
Engine oil leakage
Worn engine rings, cylinders,
valves, valve guides
Leaking turbocharger oil seals*
Restricted turbocharger oil
return or too much oil in
center housing
Carburetor or fuel injection
problem
Incorrect ignition timing,
advance, or other ignition
problem
EGR problem
Check for engine wear;
service PCV system
Inspect and correct
Check for engine wear;
check for low compression
and cylinder leakage
Replace turbocharger
Check oil return line
for restrictions and blow
out with compressed air;
check center housing for
sludge; clean as required
Inspect and correct
Inspect and correct
Inspect and correct
*Smoke and detonation indicates a leak on the compressor side;
smoke alone indicates a leak on the turbine side.
Fig. 3-28.
Turbocharger diagnosis for high oil consumption or blue
exhaust smoke.
TURBOCHARGER PROBLEMS
SOUND
CAUSE
Louder than normal noise
that includes hissing
Uneven sound that changes
in pitch
Higher than normal pitch sound
Sudden noise reduction, with
smoke and oil leakage
Uneven noise and vibration
Grinding or rubbing sounds
Rattling sound
Exhaust leak
Restricted air intake from a
clogged air cleaner filter,
bent air ducting, or dirt on
the compressor blades
Intake air leak
Turbocharger failure
Possible shaft damage,
damaged compressor or
turbine wheel blades
Shaft or bearing damage,
misaligned compressor or
turbine wheel
Loose exhaust pipe or outlet
elbow, damaged wastegate
Fig. 3-29.
Turbocharger diagnosis for unusual noises.
Содержание ASE-A8
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