Inspection of crankshaft bearings of automobile crank linkage

June 13, 2019

The function of the crankshaft is to withstand the force transmitted by the connecting rod, thereby generating torque around its own axis and outputting it to the outside. The crankshaft is supported in the crankcase by bearings, and is mainly composed of a front end of the crankshaft, a plurality of cranks, a rear end of the crankshaft, and the like. When the engine is in operation, the crankshaft is subjected to the combined action of centrifugal force and inertial force to subject the crankshaft to bending and torsional loads. In the case of secondary fixed-time maintenance, the maintenance work of the crankshaft should be cleaned and inspected. When the crankshaft wear reaches a certain level, it should be replaced or ground.

1. Crankshaft bending inspection
The crankshaft was placed on a V-shaped iron and the crankshaft radial runout was measured with a dial gauge. The maximum radial runout of the crankshaft is not more than 0.03mm. If the maximum value is exceeded, the crankshaft should be replaced or the crankshaft should be cold-corrected.
2. Inspection of the main journal and crank pin
(1) Check the outer surface of the main journal and the crank pin. There should be no obvious strain or ablation marks. Use a micrometer to measure the diameter of each main journal and crank pin. Different models of engines have different standard diameters. The Toyota Corolla 1.6-liter model has a spindle diameter of 47.988~48.000mm and a crankpin diameter of 43.992~44.000mm. If the measured diameter is not within the standard range, the radial runout of the main journal or crank pin should be checked separately.
(2) Check the radial runout of the crankshaft and the crank pin with a dial indicator, the maximum value of which is 0.004mm. If the measured value exceeds the maximum value, the crankshaft should be replaced or repaired.

3. Crankshaft bearing inspection
The method is similar to the inspection method of the connecting rod bearing, and is still inspected with a plastic gauge, the difference being the gap standard and the maximum value. The Toyota Corolla 1.6-liter model has a standard clearance of 0.016 to 0.039 mm and a maximum of 0.05 mm. If the measured value exceeds the maximum value, the bearing should be replaced and the crankshaft replaced if necessary. When replacing parts, refer to the service manual of the model.
4. Inspection of crankshaft axial clearance
Install the main bearing cap and tighten the bearing cap bolts to the specified torque. The amount of movement of the crankshaft in the axial direction is measured with a dial gauge. Different models of engines have different standard values. The Toyota Corolla 1.6-liter model has an engine crankshaft axial clearance standard of 0.04 to 0.14 mm and a maximum value of 0.18 mm. If the measured value is greater than the maximum value, replace the thrust washer with a set.

5. Precautions for crankshaft installation
(1) The upper and lower main bearings of each main journal should be installed in situ, and the installation position must not be adjusted.
(2) The upper bearing with organic oil groove should be installed on the cylinder block. When installing, the oil should not be applied on the contact surface between the bearing and the cylinder; the distance between the insulation of the cylinder and the insulation of the bearing is 0.5~1.0mm, and The two margins are equal.
(3) The lower bearing is installed on the crankshaft bearing cover. When installing, the oil should not be applied on the contact surface between the bearing and the bearing cover; the distance between the insulation of the lower bearing and the edge of the cover is 0.7mm, and the distance between the two sides is equal.

(4) The Thrust Bearing bearing one side of the oil groove should be installed outward.
(5) The bearing cover has a forward marking and should be installed in the correct direction; before installation, a thin layer of oil should be applied to the spindle neck.
(6) The bearing cap bolts shall be tightened separately from the middle to the ends by 2 to 3 times. For each bolt of a bearing cap, the crankshaft shall be rotated once.

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