Bearing shell failures may result from oil deterioration, oil contamination, or oil loss. Lubricating oil analysis may be required to determine whether corrosive acid and sulphur are present. These may cause etching, flaking and pitting. Bearing seizure may result from low oil.
Crankcase Integrity Check
Check crankcase integrity as follows:
Rotate engine so the main bearing saddles are facing upward. Wipe main bearing saddle using a lint-free cloth. The supports must be free of oil. Do not lubricate the backside of the bearing inserts.
Install upper bearing inserts into bearing saddle. Ensure the locking tangs on the bearings are snapped into the crankcase
Apply Prussian Blue to the crankshaft main bearing journals. Carefully lower the crankshaft onto the main bearing inserts in the crankcase.
Do not install the main bearing caps and lower bearing inserts at this time.
if voids appeared in the bluing transfer, the crankcase integrity is questionable.
Rotate the crankshaft 1/2 turn.
Carefully remove the crankshaft and inspect the upper bearing inserts for an even transfer of bluing from the journals to the bearings.
When satisfied that the crankcase is in good order and free of distortion and burrs around upper bearing insert seats, clean all Prussian Blue from the bearings and crankshaft journals.
Installation of Crankshaft
Install crankshaft as follows:
Lubricate the upper main bearing inserts with clean engine oil. See Figure
1. Upper Main Bearing Insert
Upper Main Bearing Inserts
Carefully install the crankshaft into the main bearing saddle. Use an appropriate lifting sling to lower the crankshaft. See Figure
Bearing Fitting Procedure
Follow these steps to fit bearings into the bearing cap:
Install a new bearing in the bearing cap, as required. Be sure the locking tangs on the bearing inserts are snapped into the bearing cap notch.
Check bearing clearance as follows:
Clean the bearing surface and the exposed half of the crankshaft journal. Ensure these surfaces are free of oil.
Install the bearing caps and lower inserts and tighten to the specified torque. Refer to section
Remove one bearing cap with insert one at a time. Remaining caps are left tight while checking the fit of the bearing with the cap removed.
Wipe the oil from all contact surfaces of the exposed journal and bearing insert and cap removed.
Place a piece of Plastigage across the full width of the bearing surface on the crankshaft journal (or bearing cap insert) approximately 6 mm (1/4 in.) off center. Install bearing cap and tighten cap bolt to specified torque. Refer to Specifications
in Section 1.A.
Do not turn crankshaft while making check with Plastigage.
When bearing clearance is checked, the crankshaft will have to be supported and held against the upper main bearing halves to get a correct Plastigage reading. Use a jack at counterweight next to each main bearing being checked to support the crankshaft. Failure to support the crankshaft will result in inaccurate readings.
Remove bearing cap with insert.
Do not disturb Plastigage. Using the Plastigage envelope, measure the widest point of the Plastigage. This reading indicates the bearing clearance in thousandths of an inch or millimeters.
If the bearing clearance is not within specifications, the crankshaft must be replaced or reground and undersize bearings installed.
Installation of Main Bearing and Cap
Follow these steps to install the main bearing caps, pistons and connecting rods.
With acceptable bearing clearance, proceed as follows:
Clean Plastigage from main bearing or crankshaft journal surface.
Coat all bearing surface journals and bolts with clean engine oil.
Place No. 1 through No. 6 main bearing caps with lower bearing inserts installed.
If end play exceeds specifications, replace thrust bearing and recheck crankshaft end play. If end play is less than specified, loosen main bearing caps, reposition, torque and check end play again.
Mount the dial indicator on crankcase with indicator tip on crankcase flange face.
Lightly pry the crankshaft forward and zero indicator.
Then pry crankshaft rearward and record dial indicator reading. Repeat to assure an accurate reading.
Install piston and connecting rod assemblies.
Install front cover.
Install oil pump assembly.
To determine if repair is possible or replacement is necessary, perform the following procedure. See Figure
Repair or Replacement of Cylinder Liner Flowchart
Use the sleeve puller to remove the cylinder liners, see Figure
, as follows:
1. Liner Puller
4. Cylinder Liner
2. Forcing Nut
5. Lifting Bridge
3. Lifting Bridge and Liner
6. Lifting Jaws
Cylinder Liner Removal
To prevent damage to the journal by the puller lifting jaws during puller installation, bar the engine over so the crankshaft journal is located at the bottom (low point) of its travel.
Position the puller in the liner and spread the lifting jaws so the tangs grip the bottom of the liner.
When you remove the liner from the puller, mark the liner with its cylinder bore number. Also mark the liner position in the block for purposes of inspection and assembly.
With the lifting bridge firmly on the crankcase top deck, turn the forcing nut to break the cylinder liner loose from the crankcase.
Lift liner and puller from the crankcase.
Use a pic to remove two (2) O-rings at the lower counterbore area of each cylinder liner.