MBE 900 – Section 1.16 Connecting Rod Bearing

Section 1.16
Connecting Rod Bearing

Do not try to repair the connecting rod bearings; replace them.‪

Section 1.16.1
Bearing Replacement

Replace the bearings as follows:‪

1. Measure the bearing journal on the crankshaft with a micrometer at two points (vertical and horizontal) and note the measurements. See Figure "Measuring the Bearing Journal" .
   

   Figure 1. Measuring the Bearing Journal

2. Calculate the average (nominal) bearing-journal diameter from these two measurements, and determine the current repair stage from the specifications listed in Table "Bearing Journal Specifications" .

   Repair Stage‪	Diameter mm (in.)‪
   Standard‪	69.995–70.015 ( 2.7557–2.7565)‪
   Undersize 0.1 mm‪	69.895–69.915 (2.7518–2.7526)‪
   Undersize 0.25 mm‪	69.745–69.765 (2.7459–2.7467)‪
   Undersize 0.5 mm‪	69.495–69.515 (2.7360–2.7368)‪
   Undersize 0.75 mm‪	69.245–69.265 (2.7262–2.7270)‪
   Undersize 1.0 mm‪	68.995–69.015 (2.7163–2.7171)‪

   Table 1. Bearing Journal Specifications
3. If new bearings are required, select bearing shells that match the current repair stage of the bearing journal.

   Note: Connecting-rod bearings for all repair stages are delivered from the factory ready to install. Do not refinish them in any way.

4. Clean the bearing contact surfaces on the connecting rod and bearing cap with a chamois.
5. Insert the bearing shells into the connecting rod and bearing cap. See Figure "Bearing Shell Placement" .
   

   1. Bolt, Connecting Rod (2 qty.)‪	3. Bearing Shell (2 parts)‪
   2. Bearing Cap‪

   Figure 2. Bearing Shell Placement

   Note: The rod and cap require different bearing shells. Make sure the abbreviated part numbers on the shells correspond to the numbers on the rod and cap.

6. Be sure the locking lugs on the shells are completely seated in the slots in the rod and cap. See Figure "Bearing Shell Placement" , and see arrow locations.
7. Lightly oil the bearing surfaces, bolt threads, and contact surface of the bolt heads.
8. Being careful not to damage the mating surfaces, place the bearing cap on the connecting rod. Match the identifying marks on the cap with those on the rod. Make sure the numbers are on the same side.

   Note: Never bolt the bearing cap tightly to the connecting rod without the bearing shells installed.

9. Install the bolts while pressing the bearing cap against the connecting rod. Tighten the bolts alternately as follows:
   1. Tighten the bolts 11 N·m (8 lb·ft).
   2. Tighten the bolts 45 N·m (33 lb·ft).
   3. Turn the bolts an additional 90 degrees.
10. Rotate the crankshaft to ensure there is no binding.