Main Bearing Replacement

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The main bearings are serviced in-vehicle. They must be replaced one-at-a-time in order to properly support the crankshaft. The upper and lower main bearing shells are NOT interchangeable. The upper and lower main bearings are "select fit" to achieve proper oil clearances. Refer to MAIN BEARING FITTING .

1. Disconnect and isolate the negative battery cable.

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2. Remove the oil pan, oil pump pick-up and engine oil pump. Refer to PUMP, ENGINE OIL, REMOVAL .
3. Remove the eight main bearing cap bolts from the windage tray in the sequence shown and remove the windage tray (1).
   Fig 1: Main Bearing Cross Bolts Loosening Sequence

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   NOTE:

   Typical V6 engine configuration shown.

4. Remove the eight main bearing tie bolts in the sequence shown.
   CAUTION:

   DO NOT use a number stamp or a punch to mark main bearing caps, as damage to main bearings could occur.

   NOTE:

   Main bearing caps are not interchangeable and are marked to insure correct assembly.

5. Mark the main bearing cap positions using a permanent ink marker or a scribe tool.

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   NOTE:

   Typical V6 engine configuration shown.

   CAUTION:

   Replace only one main bearing at a time while all other main bearing caps remain properly tightened. If all main bearing caps are removed, the weight of the unsupported crankshaft will damage the crankshaft oil seals.

   NOTE:

   Replace the main bearings in the following order; 2, 3, 1, 4.

6. Remove the two cap bolts (2) and remove the main bearing cap (1).
7. When removing the No. 2 bearing cap, also remove the thrust washers (5).
8. Slide the upper main bearing half (6) out from between the crankshaft and the engine block.
9. Inspect the crankshaft and bearings for abnormal wear patterns, scoring, grooving, fatigue, pitting and for metal or other foreign material imbedded in the lining. Refer to ENGINE BLOCK, INSPECTION .
10. If required, check the crankshaft bearing clearances by the use of Plastigage or equivalent. Refer to MEASURING BEARING CLEARANCE USING PLASTIGAGE .
11. If required, select fit new main bearings to the engine block. Refer to MAIN BEARING FITTING .
12. Lubricate the upper main bearing half (6) with clean engine oil and slide the bearing into position.

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    NOTE:

    Typical V6 engine configuration shown.

13. When installing the thrust washers (1) at the No. 2 main bearing location, use the following procedure:
    1. Move the crankshaft forward to the limit of travel. Lubricate and install the front thrust washer (1) by rolling the washer onto the machined shelf between the No. 2 upper main bulk head and crankshaft thrust surface.
    2. Move the crankshaft rearward to the limit of travel. Lubricate and install the rear thrust washer by rolling the washer onto the machined shelf between the No. 2 upper main bulk head and crankshaft thrust surface.

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    CAUTION:

    The main bearing cap bolts are tightened using a torque plus angle procedure. The bolts must be examined BEFORE reuse. If the threads are necked down the bolts must be replaced.

14. Check the main bearing cap bolts for necking by holding a scale or straight edge against all of the threads. If all of the threads do not contact the scale (2) the bolt must be replaced.

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    NOTE:

    Typical V6 engine configuration shown.

15. Lubricate and install the lower bearing half (3) onto the main cap (1).
16. Install the main bearing cap (1) with two inner main bearing cap bolts (2). Tightened to the proper specifications. Refer to TORQUE SPECIFICATIONS .
17. Repeat the previous steps for main bearings 3, 1 and 4.
18. Measure crankshaft end play. Refer to CRANKSHAFT END PLAY .

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19. Position the windage tray on to the engine block.
20. Install the windage tray with eight main bearing cap bolts. Tighten the bolts in the sequence shown to the proper specifications. Refer to TORQUE SPECIFICATIONS .
    Fig 2: Main Bearing Tie Bolts Tightening Sequence

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    NOTE:

    Typical V6 engine configuration shown.

21. Install the eight main bearing tie bolts. Tighten the bolts in the sequence shown to the proper specifications. Refer to TORQUE SPECIFICATIONS .
22. Install the engine oil pump, oil pump pick-up and oil pan. Refer to PUMP, ENGINE OIL, INSTALLATION .
23. Install the spark plugs and ignition coils. Refer to SPARK PLUG, INSTALLATION .
24. If removed, install the oil filter and fill the engine crankcase with the proper oil to the correct level. Refer to ENGINE OIL SERVICE .
25. Connect the negative battery cable.
26. Operate the engine until it reaches normal operating temperature.