Crankshaft Main Bearing - Coding System

REF. NO. 03/49

TO: OUR MERCEDES-BENZ PASSENGER CAR DEALERS

DATE: November 1994 (supercedes S.I. MBNA 03/4a, May 1993)

SUBJECT:
ALL ENGINES
CODING OF CRANKSHAFT MAIN BEARING SHELLS AND TOLERANCE MARKINGS

Due to manufacturing reasons and in the case of major engine repairs, the crankshaft main bearing shell code system is identified through various codes and markings on the crankcase and crankshaft.

Tolerance markings of the upper crankshaft main bearing shells (with oil groove and oil bore)





^ Punch marks on the crankcase/oil pan mating face next to crankshaft journal bore (1, Figure 1).

OR

^ Color code located on crankshaft journal bore in crankcase (2, Figure 1).

OR

^ Color code on the crankshaft main bearing cap.

Tolerance markings of the lower crankshaft main bearings shells (without oil groove and oil bore)





^ Color code on the crankshaft counterweight next to journal bearing (3, Figure 2).

OR

^ Punch marks on the crankshaft counterweight next to journal bearing (3, Figure 2).

OR

^ Alpha letter (i.e. G = yellow) laser etched on the crankshaft nose (4, Figure 2).

OR

^ Numeral (i.e. 37 = Blue) laser etched on the crankshaft nose (4, Figure 2).





Matching upper crankshaft main bearing shells to crankcase





Matching lower crankshaft main bearing shells to crankcase

Two additional lower crankshaft main bearing shells sizes are available, color coded white and violet in order to establish a precise crankshaft main bearing clearance. Please review the cross reference tables shown carefully before commencing the installation of crankshaft into the crankcase.

Standard size main bearings are available as spare parts with color codes in blue, yellow or red. When used according to the cross reference tables, measuring the bearings is no longer required.

When ordering standard size main bearings, use the correct code in addition to the part number:

Code 52 = color code blue,
Code 54 = color code yellow,
Code 56 = color code red.

Bearings can now be ordered individually with the additional color code from the PDC's, meaning that if more than one combination is needed, it is no longer necessary to order a complete set of bearings for each combination.

Oversize bearings must be measured according to the respective SMS repair instructions.

Connecting rod bearings are available as spare parts only with color code yellow. It is not necessary to add code 54 to the part number.