Copyright by Goodheart-Willcox Co., Inc.
334 Auto Engine Repair
Attach a dial indicator to the center housing
so that the indicator plunger extends through
the oil outlet port and contacts the shaft.
Set the dial indicator
to zero while holding
the shaft away from the
plunger tip. Read as
the shaft is moved.
Turbine wheel
Set the dial indicator
to 0 while holding
the turbine wheel
away from the
plunger tip.
Attach the indicator to
check axial clearance.
B A
Figure 16-9. Checking for turbo bearing wear. A—To measure bearing radial wear, mount a dial indicator as shown. Wiggle the
wheels and shaft up and down while reading the dial indicator. B—To measure axial clearance, mount the dial indicator on the end
of the turbo shaft. Slide the shaft back and forth in the housing while reading the dial indicator. (Ford)
6. Remove the throttle bracket.
7. Remove the waste gate actuator vacuum line.
8. Remove the EGR tube.
9. If necessary, remove the oil dipstick and tube.
10. Disconnect vacuum hoses as needed.
11. Remove the bolts attaching the turbocharger to the
intake manifold. Also, remove any braces.
12. Remove the turbocharger from the engine.
After removing the unit, place it on a workbench.
Before disassembling the unit, scribe an alignment mark on
the housing. This will allow you to reassemble the unit in
the same orientation. Then, open the housing and inspect
the interior for oil contamination.
Also, check the turbine and compressor wheels. They
should be clean and free of damage. Even the slightest
imperfection could throw the wheels out of balance and
cause severe vibration or wheel disintegration. Make sure
the turbine assembly spins freely when rotated by hand.
Also, make sure the assembly does not rub on the housing.
Figure 16-9 illustrates how to use a dial indicator
to check for radial and axial wear on the turbo bearings.
Generally, the radial wear should not exceed .003 to .006
(0.08 mm to 0.15 mm). Typical axial wear specifications
are between .001″ and .003″ (0.03 mm and 0.08 mm).
Turbocharger Service
To check the turbocharger itself, shut the engine off
and let it cool down. Remove the inlet ductwork to the
turbocharger and look inside the air intake. If you find
damage on the compressor wheel, such as parts that are
bent, broken, gouged, marred, or missing, the turbo must
be rebuilt or replaced. Figure 16-10 shows an exploded
view of a turbocharger.
Many technicians prefer to replace the entire center
section and reuse the housing or replace the complete
turbocharger to avoid repair problems. However, minor
problems, such as a bad waste gate control diaphragm,
leaking seals or hoses, or damaged housings, can be fixed
in the shop. The following discussion provides an overview
of service. Always refer to the service manual for the exact
make and model of engine or turbocharger being serviced.
Push in and pull out on the turbocharger wheel as
you spin it by hand. If you feel any bearing drag, binding,
or rubbing, the turbocharger bearings and shaft journals
are worn. A good turbocharger wheel should spin freely
and easily. Turbocharger bearing failure is often the result
of improper lubrication caused by oil breakdown or oil
contamination. Compressor wheel damage is usually
caused by foreign objects entering the turbocharger or
worn bearings that allow wheel contact with the housing.
Turbocharger clearances, shaft endplay, and runout
should be checked with a dial indicator to verify the
condition of the unit. Always refer to the manufacturer’s
specifications, since clearances vary. Typically, endplay
should be .001″ (0.03 mm) to .003″ (0.08 mm) and radial
runout should be .003″ (0.08 mm) to .006″ (0.15 mm).
If the turbocharger oil return line becomes restricted
or blocked, oil pressure can push oil past the oil seals and
into the intake and exhaust tracts. A clogged turbocharger
oil return line can cause blue engine smoke, fouled spark