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Crankshaft & Main Bearings

WARNING: This page is about a different car, the 2001 Mazda Millenia and 2001 Mazda 626. However, it is still accessible from the selected car via links, so may be relevant.
  1. Before removing crankshaft, measure and record crankshaft end play. Note that cylinder block contains a lower cylinder block section. See Fig 1. Loosen lower cylinder block bolts in sequence using several steps. See Fig 2.
    CAUTION: Do not pry on cylinder block except where indicated. See Fig 3. Note location and length of lower cylinder block bolts for reassembly reference. Bolts must be installed in proper location. See Figure.
  2. Remove lower cylinder block retaining bolts. To loosen lower cylinder block, tap on lower cylinder block while prying with a screwdriver at rear of cylinder block. See Fig 3. Separate lower cylinder block from cylinder block.
    Fig 1: Exploded View Of Cylinder Block, Crankshaft & Main Bearings
    G93E02459Courtesy of MAZDA MOTORS CORP.
    Fig 2: Lower Cylinder Block Bolt Loosening Sequence
    G00014162Courtesy of MAZDA MOTORS CORP.
    Fig 3: Identifying Lower Cylinder Block Prying Areas
    G94H47628Courtesy of MAZDA MOTORS CORP.
  3. Measure lower cylinder block bolt length of retaining bolts "A", "B" and "C". See Fig 4. Replace bolts if not within specification. See LOWER CYLINDER BLOCK BOLT LENGTH SPECIFICATIONS  table.
    NOTE: Lower cylinder block bolts "A" have a No. 4 stamped on top of bolt head and bolts "B" are stamped with an "1". Bolts "C" are the shortest bolts. Bolts "D" are outer bolts. See Figure.
    LOWER CYLINDER BLOCK BOLT LENGTH SPECIFICATIONS

    Application In. (mm)
    Bolt "A" & "B"
    Standard 5.280-5.303 (134.11-134.70)
    Maximum 5.374 (136.50)
    Bolt "C"
    Standard 4.650-4.673 (118.11-118.70)
    Maximum 4.705 (119.51)
    Fig 4: Measuring Lower Cylinder Block Bolts
    G97A08242Courtesy of MAZDA MOTORS CORP.
  4. Ensure crankshaft journal diameter, taper and out-of-round are with within specification. See CRANKSHAFT, MAIN & CONNECTING ROD BEARINGS  table under ENGINE SPECIFICATIONS.
    CAUTION: DO NOT remove fillet roll on crankshaft journals when grinding journals for undersize bearings.
  5. Crankshaft journals can be ground for .010" (.25 mm) undersize bearings if diameter is not within specification. Grind crankshaft rod journals to 2.0745-2.0749" (52.690-52.705 mm). Grind main bearing journals to 2.4287-2.4293" (61.688-61.705 mm) for undersize bearings.
  6. To check oil clearance, install upper main and thrust bearings into cylinder block. Rear (No. 4) main bearing is wider than all other main bearings. Install lower main and thrust bearings, and lower cylinder block.
  7. Coat lower cylinder block bolt threads and bolt-to-lower cylinder block surface with engine oil. Install bolts "A", "B" and "C" in proper location on cylinder block. See Figure.
    NOTE: Manufacturer does not require lower cylinder block bolts "D" to be installed when checking oil clearance.
  8. Tighten bolts in sequence to specification using several steps. Perform STEPS 1 and 2 of illustration. See Figure. Measure inside diameter of main bearings on front and rear main bearings. Subtract crankshaft main journal diameter from main bearing inside diameter to determine oil clearance.
  9. Ensure crankshaft main bearing oil clearance is within specification. See CRANKSHAFT, MAIN & CONNECTING ROD BEARINGS  table under ENGINE SPECIFICATIONS.
  10. Crankshaft main journals can be ground for .010" (.25 mm) undersize bearings if oil clearance is not within specification. Grind main bearing journals to 2.4287-2.4293" (61.688-61.705 mm) for undersize bearings.
    CAUTION: DO NOT remove fillet roll on crankshaft journals when grinding journals for undersize bearings.
  11. Install main and thrust bearings into cylinder block and into lower cylinder block. Rear (No. 4) main bearing is wider than all other main bearings.
    CAUTION: Ensure thrust bearing is installed into rear (No. 4) main bearing with oil groove facing inward.
  12. Coat all bearings and crankshaft journals with engine oil. Install crankshaft. Ensure lower cylinder block and cylinder block sealing surfaces are clean. Apply sealant onto cylinder block in specified areas. See Fig 5. DO NOT allow sealant to enter bolt holes.
  13. Install lower cylinder block. Coat lower cylinder block bolt threads with engine oil. Install bolts into proper location on cylinder block. Tighten bolts in sequence to specification using several steps. See Figure.
  14. Ensure crankshaft end play is within specification. See CRANKSHAFT, MAIN & CONNECTING ROD BEARINGS  table under ENGINE SPECIFICATIONS. Replace thrust bearing if end play is not within specification. Apply oil onto rear main seal lip and install rear main seal. Push seal in by hand and seat flush into block using appropriate driver.
Fig 5: Applying Sealant On Lower Cylinder Block
G93C02463Courtesy of MAZDA MOTORS CORP.
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