Cummins ISF3.8 crankshaft removal and installation

Removal, inspection and installation of the crankshaft of the Cummins ISF3.8 engine

The crankshaft is removed and installed during a major engine overhaul.

Crankshaft removal

  1. Remove the main bearing caps.
    • a) Check for setting marks on the main bearing caps and the cylinder block. The cap numbering starts from the front of the engine.
    • b) Unscrew the main bearing cap bolts, but do not remove them.
Removal of the main bearing caps
Fig. 1. Removal of the main bearing caps.
  1. Using 2 bolts as a lever, rock the main bearing cap and remove it. Do not damage the bolt threads.
Rocking the main bearing cap
Fig. 2. Rocking the main bearing cap.
  1. Mark the removed parts in accordance with their location.
Marking the parts
Fig. 3. Marking the removed parts.
  1. Remove the crankshaft.
  2. Remove the upper main bearing shells. Mark the relative position on the removed shell.
Removal of the shells
Fig. 4. Removal of the upper main bearing shells.
Marking the shells
Fig. 5. Marking the removed shells.

Crankshaft inspection

  1. Measure the diameter of the connecting rod and main journals of the crankshaft.
Measuring the journal diameter
Fig. 6. Measuring the diameter of the connecting rod and main journals.

Connecting rod journal diameter:

  • nominal: 68.962–69.013 mm;
  • repair (0.25 mm): 68.712–68.763 mm;
  • repair (0.50 mm): 68.462–68.513 mm.

Main journal diameter:

  • nominal: 82.962–83.013 mm;
  • repair (0.25 mm): 82.712–82.763 mm;
  • repair (0.50 mm): 82.462–82.513 mm.

Maximum ovality: 0.050 mm.
Maximum taper: 0.013 mm.

If the dimensions of one journal differ from the nominal, bore all journals to the nearest repair size.

  1. Determine the main bearing clearance using a plastic gauge.
    • Place the crankshaft in the cylinder block.
Placing the crankshaft in the block
Fig. 7. Placing the crankshaft in the cylinder block.
  • Place the plastic gauge across each main journal.
  • Install the main bearing caps.
  • Tighten the main bearing cap bolts.

Note: do not turn the crankshaft.

  • Remove the crankshaft main bearing caps.
Plastic gauge on the journal
Fig. 8. Plastic gauge on the main journal.
  • Measure the maximum width of the flattened gauge, determining the radial clearance from it. Main bearing clearance: 0.04–0.12 mm.
Measuring the flattened gauge
Fig. 9. Measuring the width of the flattened gauge.
  1. Check the length of the main bearing cap bolt shank. Maximum length: 120 mm.
Checking the bolt length
Fig. 10. Checking the length of the main bearing cap bolt.
  1. Check the thickness of the main bearing shells.

Shell thickness:

  • nominal: 2.456–2.464 mm;
  • repair (0.25 mm): 2.706–2.714 mm;
  • repair (0.50 mm): 2.956–2.964 mm.
Checking the shell thickness
Fig. 11. Checking the shell thickness.

If necessary, select a new bearing by the number stamped on the back of the old shell.

Crankshaft installation

Installing the shells in the bores
Fig. 12. Installing the shells in the main bearing bores.
  1. Install the main bearing shells, aligning the shell tabs with the grooves of the main bearing bores.
Installing the shells
Fig. 13. Aligning the shell tabs with the bore grooves.
  1. Install the crankshaft thrust bearing shell on main support No. 4.
Installing the thrust shell
Fig. 14. Installing the thrust shell on main support No. 4.
  1. Apply assembly grease (No. 3163087) to the working surfaces of the main bearings and the thrust bearing on the crankshaft side.
Applying grease
Fig. 15. Applying assembly grease to the bearing working surfaces.
  1. Make sure the guide bushes are present in the main bearing caps.
  2. Install the crankshaft.
Installing the crankshaft
Fig. 16. Installing the crankshaft in the cylinder block.
  1. Install the main bearing shells in the caps, aligning the shell tabs with the grooves of the main bearing caps.
  2. Apply assembly grease (No. 3163087) to the working surfaces of the main bearings and the thrust bearing on the crankshaft side. Do not apply grease to the back of the shell!
  3. Make sure there is no dirt or foreign particles on the main bearing cap surfaces between the cap and the cylinder block.
  4. Install the main bearing caps in accordance with the numbers marked during removal. Align the guide bushes on the main bearing cap with the corresponding holes in the cylinder block.
Installing the caps
Fig. 17. Installing the main bearing caps.

Note: make sure the caps are correctly installed in the places from which they were removed, with the numbers facing the engine oil cooler.

Cap numbering
Fig. 18. Main bearing cap numbering.

The numbering starts from the front of the engine.

  1. Lubricate the threads and under the bolt heads with engine oil.
Lubricating the bolts
Fig. 19. Lubricating the bolt threads with engine oil.
  1. Install the main bearing cap by tapping it carefully with a plastic-headed hammer. After the cap is in place, tighten the bolts. Tightening torque: 50 N·m.
Bolt tightening sequence
Fig. 20. Tightening sequence of the main bearing cap bolts.

Tighten the bolts evenly in the sequence shown in Figure 20. Complete each operation with all the bolts before moving to the next operation.

Tightening torques:

Used bolts:

  • first stage: 60 N·m;
  • second stage: 80 N·m;
  • third stage: turn a further 90°.

New bolts:

  • first stage: 120 N·m;
  • second stage: fully loosen the bolts;
  • third stage: 60 N·m;
  • fourth stage: 85 N·m;
  • fifth stage: turn a further 120°.
  1. Make sure the crankshaft turns freely.
Checking the axial movement
Fig. 21. Checking the axial movement of the crankshaft.
  1. Using a dial indicator, check the axial movement of the crankshaft. Axial movement: 0.11–0.39 mm.

If the axial clearance is greater than the maximum value, replace the main bearing thrust shell installed in the area of main journal 4. Repair sizes of thrust shells of 0.25 mm and 0.50 mm are available.