Connecting Rod Bearing: Service and Repair

11 24 571 - Replacing all connecting rod bearings (N51)





Special tools required:
- 00 2 590 00 2 590 Measurement Aid
- 00 9 120 00 9 120 Torque Angle Measuring Dial





Important!
All crank pins are connected with the crankshaft.

Modified procedure; the bearing shell colours are the same at the top and bottom.

Blue / Red bearing shell colours are no longer used in combination.





Necessary preliminary tasks:
- Removing oil pan Service and Repair.





Important!
All crankshaft crank pins are classified.

Possible classifications per connecting rod at top and bottom:

r: - Red
b: - Blue
Only one colour may be fitted per big end and connecting rod.

In direction of arrow from (1 to 2) crank pin (1 to 6).

Example:
Possible classification: rbbrrb.

Cylinder 1: - Classification Red / Red.
Cylinder 2: - Classification Blue / Blue.
Cylinder 3: - Classification Blue / Blue.
Cylinder 4: - Classification Red / Red.
Cylinder 5: - Classification Red / Red.
Cylinder 6: - Classification Blue / Blue.





Release conrod bolts (1).

Remove connecting rod bearing cap (2).





Important!
Risk of damage to cylinder wall and to crankshaft.

Gently release connecting rod from crankshaft.

Remove bearing shells (1 and 2).

Install new conrod bearing shells.

Installation Note:
Pay attention to guide lugs during installation.

Important!
All crankshaft crank pins are classified.

In each case insert only one colour of bearing shell (1 and 2) for each conrod.





Check conrod bearing clearance.

Piston in BDC position.

Determine bearing clearance, ensure that bearing points are free from oil and grease.

Fit special tool 00 2 590 (Plastigage Type PG 1) to oil-free crankshaft.

Fit bearing cap so that pairing letters match up.





Important!
Do not distort conrods or crankshaft.

Use the old conrod bolts to check conrod clearance.

Tighten down conrod bolts with special tool 00 9 120.

Tightening torque 11 24 1AZ. Mechanical Specifications





Remove bearing cap. Read off bearing clearance at width of crushed plastic thread (Plastigage) with aid of measuring scale.

Conrod bearing clearance. Mechanical Specifications

- Remove Plastigage
- Coat crankshaft and bearing shells with oil.
- Install new conrod bolts and tighten down with special tool 00 9 120.
Tightening torque 11 24 1AZ. Mechanical Specifications





Assemble engine.