[ Edited ]

If you are working on MaK engine M25 and M25C, and you need to replace the connecting rod bearings - 252601-003 with round oil holes, this might have been discontinued. It is reportedly replaced with a new one having traingular oil holes.


OLD CONNECTING ROD BEARING                                                                          NEW CONNECTING ROD BEARING

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NOTE: You'll need a new tool for the new bearing installation.


New big end bearing variant


The former standard big end bearing for M25 and M25C engines (variant-03) has been replaced by a new bearing (variant-12). This bearing was originally developed for the M25E engine, but has become the standard bearing for serial production of M25C engines as well as spare part for all M25 engines now, too.


The big end bearing var.-12 is a bearing in grid technology. Compared to a bearing with the traditional round oil bores, a bearing in grid-technology (oil grooves in triangular form) has the following advantages:



  1. Prevention of cam wear


  1. Strongly reduced tendency for cavitation


  1. No impact overload


  1. Strongly reduced lubricating oil pressure fluctuations


  1. Optimal lubricating oil flow rate for piston cooling


  1. Optimal spreading of the load bearing capacity in the main load area
  2. Increase of fatigue strength


  1. Generally higher reliability



The variant of the big end bearing can be identified by the last two digits of the bearing marking (e.g. 25 282003 corresponds to variant – 03).


We recommend that you exchange the big end bearings on all cylinders of an engine at the same time in order to stay within the regular maintenance intervals. However, from a technical point of view, a mixed use of the bearing variants mentioned above is uncritical.


When changing a bearing to the new variant, no special measures need to be taken on the crank pin as long as it is still within the wear limits.




For bearings of variant -12, you will need a new installation tool. You cannot use the tool designed for the former variants featuring round oil bores.