Connecting Rod Bearing: Testing and Inspection

Big-End Bearings

Important: When using the Plastigage to measure play, be careful not to get any in the oil holes.

Note: The crankshaft must remain absolutely still while measurement is in progress.

Before measuring bearing clearance when fitting new bearings, the ovality and taper of the crankshaft journals must be checked. Use Plastigage, part no. (45) 30 06 558, which available in three thicknesses, to measure the clearance. Use type PG-1 (green).
Measure ovality with a micrometer at two positions 90° from each other. Use Plastigage to measure clearance as follows:





1. Clean the parts to be measured so that they are dry and free from oil and dirt. Place a strip of Plastigage along the shaft.





2. Fit the bearing cap.
Tightening torques: 20 Nm + 70° (15 ft. lbs. + 70°)





3. Remove the bearing cap. The strip of Plastigage should now have adhered to either the bearing cap or the main journal.
4. Measure the width of the Plastigage strip with the scale printed on the packet and read off the clearance. One side of the packet is measured in mm, the other in 1/1000 inch. Measure the strip at its widest point but do not touch it with your fingers.
For measurements, refer to Specifications