Crankshaft Main Bearing: Service and Repair

Crankshaft Main Bearing Replacement

Main Bearing Clearance Inspection

1. Remove the bearing cap bridge and the bearing halves Crankshaft And Piston Removal.

2. Clean each main journal and the bearing half with a clean shop towel.

3. Place one strip of plastigage across each main journal.

4. Reinstall the bearings and bearing cap bridge, then torque the bearing cap bolts to 25 N-m (2.5 kgf-m, 18 lbf-ft) in the proper sequence.

NOTE:

- Apply new engine oil to the bolt threads and flanges.
- Do not rotate the crankshaft during inspection.





5. Tighten the bearing cap bolts an additional 40 °.

6. Remove the bearing cap bridge and the bearings halves, and measure the widest part of the plastigage.

Main Bearing-to-Journal Oil Clearance










7. If the plastigage measures too wide or too narrow, remove the crankshaft, and remove the upper half of the bearing. Install a new, complete bearing with the same color code, and recheck the clearance. Do not file, shim, or scrape the bearings or the caps to adjust clearance.

8. If the plastigage shows the clearance is still incorrect, try the next larger or smaller bearing (the color listed above or below that one), and check the clearance again. If the proper clearance cannot be obtained by using the appropriate larger or smaller bearings, replace the crankshaft Crankshaft And Piston Removal and start over.

Main Bearing Selection

Block Bore Code Location

Letters have been stamped on the end of the engine block as a code for the size of each of the five main journal bores.

Use them, and the numbers or bars stamped on the crankshaft (codes for main journal size), to choose the correct bearings. If the codes are indecipherable because of an accumulated of dirt and dust, do not scrub them with a wire brush or scraper. Clean them only with solvent or detergent.










Main Journal Code Location