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Home >> BMW >> 1972 >> 3.0CSi Automatic Trans >> Repair and Diagnosis >> Engine Mechanical >> Mechanical >> BMW Engines - 2500, 2800, 3.0 & BAVARIA 6 Cylinder >> 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). Color code designation is given is specifications.
    Fig 1: Crankshaft Markings
    G09325562Courtesy of BMW OF NORTH AMERICA, INC.
  4. Check main and connecting rod bearing clearance with the Plastigage method. If bearing clearance is more than specified, crankshaft must be ground to next undersize. Bearings for undersize crankshafts are available in 0.010" (0.25 mm) and 0.020" (0.50 mm) undersize.
  5. Install bearing halves in crankcase and bearing caps. Lubricate crankshaft bearing journals and install crankshaft in crankcase.
  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.
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