TM 10-3930-660-34 3-9.  CRANKSHAFT MAIN BEARINGS - REPLACE (Cont’d) g. Repeat  STEPS  a  through  f  for  remaining main    bearings    2    through    5    and    thrust bearing (5) at main bearing position 6. CLEANING CAUTION Never   use   any   type   of   rough   material   or tools  such  as  sandpaper,  emery  or  crocus cloth, files, or glassbead cleaning equipment to clean bearings. 1. SEE CLEANING INSTRUCTIONS, PARA.  2-10. 2. APPLY    A    LIGHT    COAT    OF    OIL    OVER    THE BEARINGS AND THE BEARING SURFACE IN THE BEARING   CAPS   IF   THE   BEARINGS   ARE   NOT GOING  TO  BE  INSTALLED  WITHIN  ONE  HOUR AFTER CLEANING. INSPECTION 1. INSPECT MAIN BEARINGS AND THRUST BEARING.  REPLACE BEARING IF: back  of  bearing  shows  that  fretting  has  taken place, back of bearing has a mirror-like (shiny) finish, there are scratches in the bearing surface which do not disappear after cleaning, bearing  surface  has  material  damage  such  as cracks or flaking, there is a hole in the bearing surface, bearing shows wear on the mating face, bearing oil hole is distorted, there are hot spots in bearing surface, and/or bearing has damage to the tab. 2. INSPECT  THRUST  BEARING  FLANGES  FOR DAMAGE.    IF  DAMAGED,  REPLACE  THRUST BEARING. 3. INSPECT    MAIN    BEARING    BORES    IN    THE BLOCK  FOR  CRACKS,  CHIPS,  DISTORTION, THREAD    DAMAGE,    OR    OTHER    DAMAGE. REPLACE   CYLINDER   BLOCK   IF   THERE   IS BEARING BORE DAMAGE. 4. INSPECT AND MEASURE CRANKSHAFT MAIN BEARING JOURNALS, PARA.  3-8. 5. INSPECT MAIN BEARING CAPS FOR CRACKS,   FRETTED   OR   CHIPPED   MATING SURFACES,     DISTORTION,     OR DAMAGED RING DOWELS. a. Replace a damaged bearing cap. b. Replace both bearing cap ring dowels if one or both are damaged. INSTALLATION 1. INSTALL  MAIN  BEARINGS  2  THROUGH  6  (3 AND 4) FOR MAIN BEARING CLEARANCE CHECKS. a. If main bearings are coated with oil, remove oil with a clean wiping rag. CAUTION To   help   prevent   damage   to   the   cylinder block   during   main   bearing   bore   cleaning, compressed   air   shall   not   exceed   15   psig. Use  compressed  air  only  with  effective  chip guarding and personal protective equipment. 3-69