AH03.20-B-1000-02A | Information on assessing wear of main bearings and main bearing journals | ENGINE all | |
The following indications should assist in the evaluation of the bearing shells and their journals, for a professional decision on their state regarding their reuse.
The damage frames, represented next, are only an excerpt of the possible forms of damage of the bearing shells and their journals. In the evaluation of damage forms, the condition of the crankshaft journal surface must always be included in the damage diagnosis.
Wear or damage on the bearing shells and their journals are frequently caused by:
- too little engine oil, poor engine oil quality (viscosity) or thinning of the oil by fuel,
- soiled or damaged engine oil filter,
- a fault in the engine oil circuit; e.g. the engine oil pressure is too low,
- too small or too large turning play between the connecting rod bearing shells and their journals, or
- inadequate cleaning during engine repair.
Before starting the engine after an engine repair, fill the engineoil circuit with approved engine oil. Next, starter crank the engine several times, until oil pressure builds up.
W03.20-1023-81
Undamaged bearing shell
The bearing shell is uniformly smooth over all its surface, without apparent striae and without wear on the sliding layer.
The bearing shell can be reused.
Measuring traces on the bearing shell surface are normal, they are formed in the bearing shell manufacture by the measuring process.
W03.20-1024-81
Bearing shell with normal turning traces
The bearing shell is uniformly smooth over a large part of its surface, without apparent striae and without wear on the sliding layer.
The bearing shell can be reused.
W03.20-1025-81
Bearing shell with ample wear surface of sliding layers
The sliding layer is worn out, the bearing shell material situated below is uncovered, the wear point is clearly visible by the shiny point on the bearing surface.
Worn out by long operating period, replace the set of bearing shells. If one engine bearing shell needs to be replaced, all must be changed.
W03.10-1018-81
Bearing shell showing wear on the face
A bearing shell strongly worn on its face (arrow) is worn out
The unilateral face wear is caused by bearing journals taper machined, taper hole in the engine block or a too large radial rounding between the bearing journals and the face of the crankshaft. A non calibrated crankshaft can be the other cause (excessive deformation caused by oscillation).
The face wear on both sides is caused by concavely machined bearing journals, concave hole in the engine block or a too large radial rounding between the bearing journals and the face of the crankshaft.
Do not reuse the bearing shell, it must be replaced. Thecrankshaft and the crankcase bore must also be checked fordamage.
W03.20-1030-81
Rolling surfaces of crankshaft bearing journals, undamaged
The rolling surface of the bearing journal is uniformly smooth on the entire surface and without visible striae.
The crankshaft can be reused, if all treads of the crankshaft areOK.
W03.20-1031-82
Rolling surfaces of the crankshaft bearing journals with normal turning traces
The rolling surface of the bearing journalis uniformly smooth on the entire surface and without visible striae.
The crankshaft can be reused, if all treads of the crankshaft areOK.
W03.20-1032-82
Rolling surfaces of the crankshaft bearing journals with light striae and scratches
Score marks and scratches are visually and perceptibly thin on thetreads.
The crankshaft can be reused, when all other rolling surfaces of the crankshaft are in order and the diameter of the bearing journals are still within tolerances, therefore, measure the bearing journals.
Individual dirt scores and scratches are not critical. A light metal coating on the rolling surface of the bearing journal can be eliminated by polishing with some cleaning material, for. ex., Sidolin range cleaner, the crankshaft must be turning for this.
During maintenance and repair work, check engine oil and engineoil filter for contamination, replace if necessary.
W03.20-1033-82
Rolling surfaces of the crankshaft bearing journals with strong striae
Score marks on the surface are clearly visible and noticeable to thetouch.
These are due to:
- dirt and foreign objects in the engine oil circuit, for exampledue to a faulty engine oil filter, use of grinding materials orinsufficient cleaning after an engine repair
- very little engine oil pressure (insufficient lubrication).
Measure the diameter of the crankshaft bearing journals, eventually machine to the next repair stage.
If reworking is no longer possible, the crankshaft must be renewed.
W01.40-1040-81
Thrust bearing wear evaluation
Thrust plate undamaged
The entire bearing surface of the thrust plate is smooth and even,with no visible scoring, and the oil pockets (arrows) are clearlyvisible on both sides of the thrust plate.
The thrust plate can be reused, but only if all thrust plates haveno damage, otherwise all thrust plates must be replaced.
If one thrust plate is damaged, all the thrust plates must bereplaced. Only thrust plates of the same thickness must be installedor used.
W03.20-1026-81
Thrust plate with thin score marks and scratches on thebearing surface
The bearing surfaces of the thrust plates are slightly visible andperceptible on the bearing surface.
The thrust plate can be reused, but only if all thrust plates haveno damage, otherwise all thrust plates must be replaced.
Individual dirt score marks and scratches are not critical, they arecaused by fine-grained dirt particles in the engine oil circuit.
W03.20-1027-81
Thrust plates with thick score marks
Score marks on the bearing surface are clearly visible andnoticeable to the touch.
The score marks are caused by:
- dirt and foreign objects in the engine oil circuit, for exampledue to a faulty engine oil filter, use of grinding materials orinsufficient cleaning after an engine repair
- very little engine oil pressure (insufficient lubrication).
The thrust plates are not reusable and must be replaced. If a thrust plate is worn, all thrust plates must be replaced.
W03.20-1028-81
Worn thrust plate
There has been a reduction of material on the axial washers (flywheel side), so the oil pockets are no longer visible.
The thrust plates are not reusable and must be replaced. If a thrust plate is worn, all thrust plates must be replaced.
In case of a worn out axial washer, it becomes necessary to additionally check the bearing thrust, the main bearing and the journals.
The stock removal on the reverse side was caused by natural vibrations of the thrust plate, this can be a result of a too large crankshaft end play.
W03.10-1018-81
Bearing shells in main bearing caps and thrust bearing are worn out
The bearing shell with a strong lateral face wear (arrow) is worn out.
Do not reuse the bearing shell, it must be replaced.
Additionally are to be checked the main bearing caps and the thrust bearing cap and the journals for damage.
Wear to one side is caused by striking of the crankshaft counterweight, which is in turn caused by excessive crankshaft axial play or a worn thrust plate.
W01.40-1038-81
Check the main and thrust bearing caps and the thrust journals (1).
In the case of damage (arrow) in the main and thrust bearing caps or on pins (1) by the crankshaft counterweight, the crankshaft and the pin (1) in the main bearing caps will have to be replaced.
W01.40-1039-81
In no case are to be replaced only the axial washers (2) in the case of worn pins (1), i.e., too short,otherwise, the axial washers (2) can become loose by the self-oscillation and be twisted, this may cause engine damage. The pin (1) in the thrust bearing shell cap has to be replaced.