that thrust collar thrust bearing, or thrust bearing
surface of the back plate assembly are worn.
play is less than .001, it indicates a carbon build-
up behind the turbine wheel. Unit must be disas-
sembled and condition corrected.
(2) Check the shaft radial movement (specified
radial movement is .003 to . 007). Proceed as
(a) Attach a dial indicator adapter to the oil
discharge outlet, or fabricate an adapter by threading
the end of a rod approximately 8 long. Secure the
rod to the turbine housing. Attach the dial indicator
with appropriate extensions to the adapter.
(b) Position the point of the dial indicator,
through through oil discharge outlet, on the center of the
(c) With one hand on the compressor im-
peller and-one hand on the turbine wheel, pull the
shaft up against the indicator. Record the indicator
(d) With one hand on the impeller and one
hand on the turbine wheel, push the shaft down, away
from the indicator. Record the indicator reading.
(e) The difference between the readings re-
corded in steps (c) and (d) will be the total shaft radial
Repeat the procedure several times be-
fore accepting a final figure.
(f) If the radial shaft movement exceeds
,007, it is an indication of shaft or bearing wear,
or that the bearing bore in the center housing is worn.
The unit must then be disassembled and reconditioned.
h. Use a sliding T handle and a 3/8 inch, 12
point socket and remove the locknut (8). Hold the
T handle at the ends to prevent bending of the shaft.
i. Twist and pull up to remove the compressor
j. Remove the metallic seal ring from the groove
on the turbine impeller shaft.
K. Remove the thrust bearing (17) and thrust
collar (16) as a unit.
Separate bearing and collar.
1. Remove the metallic sealing ring (20) from the
thrust colIar (16)
Since the outer bearing retainers and
bearings may be removed from either end
of the center housing, it is not necessary
to remove inner bearing retainers unless
inspection reveals them to be damaged or
unseated. Always replace bearing retainers.
m. Remove outer bearing retainers with a sharp
pointed tool such as an ice pick; use a twisting motion.
Use care to avoid scoring bearing or bearing bore.
14-53. Turbocharger Cleaning and Inspection.
Refer to Operator and Organizational Maintenance
14-54. Turbocharger Repair,
a. If the turbocharger is damaged due to lack of
lubrication and results in bearing seizure, or if the
impellers are damaged due to foreign objects passing
through the turbine or compressor, the damage will
be extensive and require replacement of the rotating
parts and possibly the replacement of the center
housing. This must be determined by inspection.
At the time of engine overhaul the turbocharger must
be disassembled and all parts inspected.
b. Burnish or polish out minor surface damage
using silicon carbide abrasive cloth for aluminum
parts and crocus cloth for steel parts; clean before
reassembling with cleaning solvent Federal Specifi-
c. At time of repair or overhaul, replace rubber
seal ring, metallic seal rings, bearing retainers, and
d. Make certain all parts are thoroughly clean
and-work bench area is clean and free of any abrasive
material before proceeding with inspection of indi-
e. Replace bearings if they indicate signs of
scoring, nicks, shellac-like deposits, or other
Use a micrometer and telescoping
gauge and measure the diameters. The bore of the
impeller shaft bearings must not exceed 0.4019
inch and the outer diameter must not be less than
Replace bearings at time of overhaul.
f. The thrust bearing must not show any signs of
scoring or foreign matter deposit on the grooved
Measure the thickness at three places along
the collar bore.
The measurement must not be more
than 0.1720 or less than 0.1711 inch. Replace the
thrust bearing at time of overhaul.
g. The bore for the metallic seal ring must not
indicate signs of scoring or roughness.
bore must be clean and smooth. The size of the bore
must not exceed 0.5015 inch.
Replace if this mea-
surement is exceeded.
h. Make certain that the turbine and compressor
housing are clean and have no internal obstructions
that could impede the flow of gases. Replace
i. The compressor impeller must not show any
signs of rubbing with either the compressor housing
or the backplate.
The bore must be smooth. The fit
should be 0.0002 inch to 0.0004 inch. The blades
must be totally free of dirt or any other foreign sub-
The blades must not be bent, cracked, or
eroded to a feather edge.
Replace compressor im-
peller if these requirements are not met.
Change 3 14-59