Mission Impossible: Replacing Connecting Rod Bearings in Japan

BMW M3 ownership is a lot of fun, but also comes with fair share of responsibilities, with frequent oil changes and routine maintenance schedules are only part of it..

For anyone who does not own a Naturally Aspirated M3 (or M5), this may sound like a horror story, but for us, especially the E9x and E6x owners, this is just part of the equation.

Our state of the art high revving engines come with Achilles heels and attending to them on-time may be what stands between enjoying your M car and having to pay up to 20000 dollars for a replacement engine.

This is how these engines may end up!

Yes,we all heard horror stories of engines blowing up in the middle of track day or as people try an overtake on an autobahn.

So what causes it? BMW derived S65 and S85 engines from DTM engines, so what makes them so awesome also makes them for the lack of better word "weak", and failure rate is so significant that M3Post hosts a repository of blown engines on their site!

I am no engineer so I can only guess what was the reason for such small clearances, but I guess it would be relevant to oil pressure requirements, how well engine responds to throttle inputs, and so on,

And then there are the bearing themselves, which BMW made out of aluminium - not the most solid metal, although very light and resistant to corrosion.

For starters, aluminium is a sub-optimal way of manufacturing rod bearings.  Simply put, there are better options - starting from the famous BE bearings to ACL ones that I used in my setup -- all made out of tri-metal alloys to remain corrosion free, while being a lot more solid and resistant to metal fatigue, yet soft on the crank if you end up spinning them.

Replacing rod bearings seems to be the standard process world-wide, but in Japan it's a whole different situation.  People don't drive their cars that much, and many have extended warranties, which puts the burden of replacing these engines on BMW themselves.

A fun little stat out of BMW Japan is that Japan has the most blown low mileage S65 motors in the world... Again, because they simply don't drive their cars!  Plus apart from me, most BMW owners are pretty wealthy so they shell out thousands of dollars at BMW dealerships despite places like Check Shop being more than capable of doing higher quality repairs from fraction of the cost!

What that meant for me was that there was no shop that would commit to doing the work! Except for above mentioned Check-Shop in Yokohama, yes same place that has done my suspension, wheels, tires, and generally looked after my M3 and has always been friendly to my limited budget.

This was their first rod bearing replacement on the S65 engine, but they are hoping to do more, because results are...

Well, see for yourself... This wear is not normal for 50000 km!

They also found shredded metal particles in the oil pan!


Let me repeat: only 50k km on my car! Luckily nothing like in the previous video.  They confirmed that new clearances were larger, yet within BMW recommendations and there was no damage to the crank.

I think BMW has some explaining to do!

While at at it, please also explain throttle actuators, which fail on pretty much every S65 and S85 engine, because genius engineers at BMW thought it was a good idea to reuse cheap plastic gears made for instrument cluster in the device that controls air flow into the combustion chamber!

Then there is leaking leaking DCT oil pan, which sits next to catalytic converters and for some reason made out of cheap plastic as well! How about front underbelly made out of... Yes you guessed it! cheap plastic, which tends to self destruct after certain distance... Why BMW, Why are your cars riddled with time bombs, which are never addressed?

More on these later, but for now, the wizards at Check Shop have put everything back together and car feels better than it ever was!

I am not joking! Increased clearance, coated bearings, fresh oil, replaced engine mounts all contribute to a lot smoother and more responsive engine.

Yes, there is a lot more work to be done, and Check Shop is the place!

I can't resist recommending Check Shop to the car community around me!  CEO and founder Naohiko Otsuka is a no bullshit kind of guy - very direct and doesn't waste time, yet at the same time fair and objective, always looking out for his customers.

Maybe this is why there is a strong sense of community among customers as we always interact, chit chat, and when needed, help each other out!  It's a different world out here, one which I am very proud to be a part of!




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