M Coding

Let's talk connecting rod bearings on S55 engines
Conrod bearing failure is definitely less common than on the N55, largely due to improved oil pickup and bearing clearances. That said, rod bearings on the S55 are not completely immune to wear, especially on higher mileage engines, aggressively driven cars, or vehicles that see frequent high RPM use, track time, or extended oil change intervals.
Key here is monitoring oil condition, listening for unusual bottom end noise, and considering preventative maintenance

This 145k km example came in for conrod bearings due to glittery oil in the filter housing which was well spotted by the owner.

So off with the subframe to do the following:
✅Mahle Motorsport bearing set
✅Genuine conrod, oil pump and sump bolts
✅Genuine Sump gasket
✅Genuine Breather pipe
✅Sacrificial oil and Liqui Moly engine flush
✅Liqui Moly Molygen engine oil
✅Genuine rear differential fluid
✅iStep update
And to top it all off
✅GTS software flash.

As you can see in photos, while all conrod bearings were showing signs of wear, cylinder 5 bearing had considerably more worn upper and lower conrod bearings. We suspect excess silicone to be the cause from a previous attempt at oil pan sealing by another garage.

All bearing clearances were plasti-gauged for peace of mind.
Meticulous cleaning of all components, all torqued to spec.