In the following repair procedures, minor scoring is defined as shallow scratches that do not
exceed 0.003 inch (0.08 mm) in depth. A fingernail will catch and hang up when soaped
across an excessively scored surface.
Replace the compressor housing (3) if it is cracked, deeply scored, or grooved in the contour area, or
shows signs of heavy impeller rub. Remove minor scoring and rust with crocus cloth, P-C-458.
Replace the turbine housing (7) if it is cracked, deeply scored, or grooved in the contour area, or shows S
of heavy turbine rub or burning. Remove minor scoring with crocus cloth, P-C-458.
Replace the center housing (18) if it is cracked, burned, deeply pitted, or if the bearing bore is out-of-round
or worn larger the 0.9835 inch (24.981 mm).
Replace the backplate (17) if it is cracked, deeply scored, or grooved. Remove minor scoring' with
crocus cloth, P-C458.
Replace the shroud (12) if it is cracked, deeply scored, or grooved. Remove minor scoring with crocus
Replace the impeller (9) if it is cracked, deeply scored or grooved, or shows heavy rub damage. Remove
minor nicks and scoring with cloth, P-C458.
Replace or repair the turbine wheel and shaft as follows:
Replace the turbine wheel if it is cracked, deeply scored or grooved, or shows heavy nib damage.
Remove minor nicks and scoring with crocus cloth, P-C458.
Replace if more than one visible hole over 0.080 inch (2.03 mm) in diameter is found in the weld area.
Replace if the weld area is chipped, cracked, or scored.
Porosity in the weld area is acceptable, provided the holes are not over 0.015 inch (0.38 mm) in
Surface cracks in the weld area are 4zoe . provided the maximum length is 0.375 inch (9.53 mm), no
more than three cracks are present and the distance between the cracks is at least 0.250 inch (6.35
Replace if the seal ring-to-groove clearance exceeds 0.008 inch (0.20 mm), or if the shaft runout
exceeds 0.0005 inch (0.013 mm).
Replace if the shaft is worn more than 0.6250 inch (15.875 mm) at either bearing area.
If it was necessary to replace the impeller, or the turbine wheel and shaft the turbine wheel and shaft must
be balanced individually, and then balanced with the impeller as an assembly. Balance as follows (see
Figure 9-75 and Figure 9-76).
Mount the turbine wheel and shaft in a dynamic balance machine with the rollers centered on the
bearing areas, and the drive belt centered between the rollers (see Figure 9-75).
Turn the turbine wheel and shaft at 3000 r/min, and balance to a tolerance of 0.0003 ounce-inch (0.216
mg/m). To achieve balance, use a die grinder and rotary file, and remove metal from the areas
indicated in Figure 9-75 as necessary. Smooth and blend the filed areas with crocus cloth, P-C 458.