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Home >> BMW >> 1978 >> 630CSi Standard Trans >> Repair and Diagnosis (Single Page) >> Engine Mechanical >> Mechanical >> 5301, 633CSI & 733I 6 Cylinder >> Crankshaft Main & Connecting Rod Bearings >> Main & Connecting Rod Bearing Service

Main & Connecting Rod Bearing Service

  1. With engine removed, remove clutch, flywheel, cylinder head, oil pan and timing chain. See TIMING CHAIN REPLACEMENT . Remove rear main bearing oil seal mount.
  2. Remove pistons and connecting rods. Remove main bearing caps and lift out crankshaft. Thoroughly clean and inspect crankshaft. Blow out oil passages with compressed air.
  3. Main bearings journals are manufactured in two standard sizes. Sizes are designated by a colored dot on crankshaft balance weight next to individual journal (see Fig 1).
  4. Check main and connecting rod bearing clearance using Plastigage method. If clearance will not meet specifications when installing new bearings, it will be necessary to exchange crankshaft. Crankshaft is tenifer treated and may only be reground at the factory.
  5. Install bearing halves in crankcase and bearing caps. Lubricate crankshaft bearing journals and install crankshaft in crankcase.
    NOTE: In the event of a crankshaft of a different color code than the crankcase, use one blue and one red bearing shell for each journal. Make sure that all red or all blue shells are installed facing up and the remaining color facing down.
    Fig 1: Crankshaft Color Code Markings
    G09334311Courtesy of BMW OF NORTH AMERICA, INC.
  6. Install bearing caps with numbers on caps running from one through six in order from front to rear. Install caps with bearing locks on same side as bearing locks in crankcase.
  7. Tighten caps to specifications. Check crankshaft endplay. See THRUST BEARING ALIGNMENT . To install remaining components, reverse removal procedure.
    NOTE: Ground crankshafts are marked with painted stripes (See Fig 2).
    Fig 2: View Showing Crankshaft Undersize Markings
    G09334312Courtesy of BMW OF NORTH AMERICA, INC.
CRANKSHAFT JOURNAL SIZES

Connecting Rod  In. (mm) 
  Standard 1.888-1.889 (47.97-47.99)
  1 paint stripe 1.852-1.853 (47.72-47.74)
  2 paint stripes 1.851-1.852 (47.48-47.49)
  3 paint stripes 1.850-1.851 (47.22-47.24)
Main Bearings Red Code  In. (mm) 
  Standard 2.361-2.362 (59.98-59.99)
  1 paint stripe 2.324-2.325 (59.73-59.74)
  2 paint stripes 2.323-2.324 (59.48-59.49)
  3 paint stripes 2.322-2.323 (59.23-59.24)
Main Bearings Blue Code  In. (mm) 
  Standard 2.361-2.362 (59.98-59.99)
  1 paint stripe 2.324-2.325 (59.72-59.73)
  2 paint stripes 2.323-2.324 (59.47-59.48)
  3 paint stripes 2.322-2.323 (59.22-59.23)
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