First I would like to apologise to Eric, as this second-guessing can come across as rude on a forum. He is just dealing with the facts that he has before him, and I'm happy to admit that everything I'm saying is purely conjecture.
My earlier suggestion of looking at the EPC was just to at least try to see if there was any hard evidence of a change in '09. Neither of us want anyone to buy a 315 without knowing what they are potentially buying into.
So today Eric and I looked at the EPC, but you can't buy the block (and caps) separately. You need to buy the whole complete engine - which only has the one part number option. The crank is listed separately, but still only the one option. So there is no way of proving any physical changes without eyeballing the actual parts.
Eric's sub-theory is that it may be some kind of software change that fixed it for '09. I'm not sure how to prove this conclusively.
So Erics '09 theory is based solely on the fact that he has not heard about any '09 315s blowing up. vs. plenty of '07s. He has seen a few '09s with high km, but he acknowledged that he doesn't know any of the history of the engines in these examples.
It would be nice to be able to prove this either way, but we would need more data points. Does anyone have any ideas on how this could be tested? Does anyone know of an '09 that has suffered the bearing issue?
My thoughts about the '09 theory are:
1. If they changed something inside the engine in '09, then any '07s that had official MB rebuilt engines after 2 years should also have the fix.
2. If it was a software change then the difference should be able to be felt in a road test, or definitely on a dyno, but why wouldn't MB just do that SW change to the '07s as well? It is conceivable that MB could reduce the low-down torque output in the ECU mapping while still maintaining the maximum output at high revs, but then this would nullify any torque figures they published at the time eg "330Nm from 1800rpm". I'm not sure how they could sell '09s with lower than published figures.
3. If MB changed something in '09 that fixed this, why was the ambo service still having "
systemic fault in ambulance engines amid a spate of engine failures and fires through late 2011 and 2012" and MB allowed themselves to be dragged before an inquiry over it? - it would have made sense for them to just apply this '09 fix and not have the bad publicity.
4. If it was fixed in '09, why was the OM646EVO production run so short in the Sprinter, compared to all the other Sprinter engines? It was only 2 years, the next shortest is 6 years (OM611/2), and longest is the OM642 at 12 years and counting. Even the OM651 (replacement for the OM646EVO) had an 8 year run.