Rod Bearing Break-in (hint: there isn't a need)

[old///MFanatic]

True, but nor do they have a full factory warranty commitment to deal with. Just the 2 years on the repair, no?

True, but Unlimited miles/2 years. Hard to see BMW now would rather risk major engine damage from rod bearings not telling (of the need for a break-in procedure and a 50¢ sticker) than just continue to do so as before. It costs them basically nothing to say follow (the previous) “break-in” procedure if there is any danger. If truly an issue this would prevent any potential prior 2 year warranty claims on bearing issues if break-in was indeed a factor.
No reason for BMW not to just do it then still if actually an issue, no?
Seems more plausible that they’ve stopped it because their engineers found not necessary and S54 data since campaign has confirmed no break-in needed.
Humbly this is just my take on it.

[jbfrancis3]

Another engineer who has written several hundred TSBs for another OEM. Engineers write these bulletins along with a technical service writer who helps translate them for service technicians. They are then published into the network for technicians to access freely. Nobody else has any input into these documents from the technical aspect.

Recalls are another story, because they are managed by a separate team that specializes in those matters. Since this was not a recall per se, there is no reason to view the original service bulletin with skepticism. I can personally vouch for the fact that we are doing our best to fix the customer's car using safe and effective techniques and practices. Random engineers who don't give a F about engines don't end up in those roles. They care and they were trying to fix a quality issue.

Is it common for temporary limited operating conditions to be added significant engine or chassis-related work as a precaution?

[Obioban]

A post by IamFODI from another thread, but seems applicable here I made it not quoted text because it was interfering with readability:



Yes, rod bearings are supposed to be lubricated to the point that there is zero metal-on-metal contact. If that actually panned out in practice, there'd be no need for replaceable bearings. We'd just bolt the rods to the crank and be on our way. No need for all the expense and trouble of designing, manufacturing, speccing, and installing engine bearings, all of which is an engineering rabbit hole unto itself.

Also, "lubricated" vs. "metal-on-metal" is not a binary thing. There are all kinds of intermediate regimes, some of which involve contact that is not enough to cause seizure. Hence the fact that engine bearings have a finite lifespan, which is why we're having this conversation in the first place.

All of this is why literally every engine bearing manufacturer has guidelines for what constitutes "normal wear." None of them ever says your bearings should look like new unless something's horribly wrong.

Glyco, one of the main engine bearing manufacturers, has even described some amount of wear as not just normal but beneficial in some cases:

If the clearance is minimal there is good conformability between the bearing and crankshaft journal. This conformability is a result of material that is worn in some parts of the bearing in the order of magnitude of μms. This process leads to less local stress on the sliding layer, a better absorption of shock loads and less wear.

They have also published break-in instructions for some of their bearing types, e.g.:


Those intervals sure seem short, so maybe that doesn't do much to support a break-in period of hundreds of miles. Then again, it's probably not unreasonable to imagine that some people would take several hundred miles to rack up a minute of ~4k RPM usage ("1/2 n_MAX"), especially while they've been told to go easy on the car -- which they evidently should, given everything else above.

Does any of this directly support any given statement that S54 rod bearings take X miles to break in? No. What it does is suggest that rod bearing break-in shouldn't be dismissed out of hand, and that the whole "rod bearings shouldn't wear" idea is false.

Maybe they need hundreds of miles to break in, or maybe they don't. Maybe it's different for different materials, engines, clearances, etc. This is where engineering expertise becomes important, and in cases like this it's almost always best to listen to the folks who designed the machine.

[Albino09]

Is it common for temporary limited operating conditions to be added significant engine or chassis-related work as a precaution?

No, it is not common, but also it is uncommon that any OEM would be changing rod bearings at a dealership. These days, they would install a brand new engine and collect the old one for the engine plant to do a full teardown analysis (if it's within the warranty period). Since this was a service action, it is most likely they completed a few teardowns, found the root cause (bearing quality issue), and put together a repair procedure that appropriately fixes the issue without the expense of replacing a complete long block.

Ignoring what the engineers determined was best practice because of some anecdotes isn't a good idea. Anecdotes aren't data points. At the end of the day, we're all talking about a $60 oil change and not driving like a moron for 1,500 miles. Not a huge ask.

Those intervals sure seem short, so maybe that doesn't do much to support a break-in period of hundreds of miles. Then again, it's probably not unreasonable to imagine that some people would take several hundred miles to rack up a minute of ~4k RPM usage ("1/2 n_MAX"), especially while they've been told to go easy on the car -- which they evidently should, given everything else above.

This ☝

[old///MFanatic]

Ignoring what the engineers determined was best practice because of some anecdotes isn't a good idea. Anecdotes aren't data points. At the end of the day, we're all talking about a $60 oil change and not driving like a moron for 1,500 miles. Not a huge ask.

The engineers for BMW removed the break-in period. And they never had a follow-up oil change.
So where does that leave this reasoning of following their engineers?

[Estoril]

The engineers for BMW removed the break-in period. And they never had a follow-up oil change.
So where does that leave this reasoning of following their engineers?

For model year 2006 - the Break-in period was specified followed by a BMW-specified (and free) fluid change. They provided MY2006 buyers with written instructions that specified that.

[old///MFanatic]

For model year 2006 - the Break-in period was specified followed by a BMW-specified (and free) fluid change. They provided MY2006 buyers with written instructions that specified that.

2006 builds didn’t fall under the campaign.
True original owners had “engine break-in” when new and oil change paid for. I have those receipts too.

We had oil change when bearings were done, not a follow up. Perhaps this is what you’re reading? *It even states this directly on the Service Bulletin documents.

For years now BMW does not mandate a break-in on S54 rod bearing service. I can’t find the exact date but there’s mention it was dropped during the E9x corresponding period. TIS shows no break-in for S54 bearing service currently. They just kind of quietly dropped it.

[Estoril]

2006 builds didn’t fall under the campaign.
True original owners had “engine break-in” when new and oil change paid for. I have those receipts too.

We had oil change when bearings were done, not a follow up. Perhaps this is what you’re reading? *It even states this directly on the Service Bulletin documents.

For years now BMW does not mandate a break-in on S54 rod bearing service. I can’t find the exact date but there’s mention it was dropped during the E9x corresponding period. TIS shows no break-in for S54 bearing service currently. They just kind of quietly dropped it.

I'm an original MY2006 owner - still. I'm not reading anything - I recall it clearly.

The way it worked and what new owners were told are as I originally wrote.

[Albino09]

The engineers for BMW removed the break-in period. And they never had a follow-up oil change.
So where does that leave this reasoning of following their engineers?

I was merely commenting on some of the misinformed comments about whether or not to trust the service bulletins.

[old///MFanatic]

I was merely commenting on some of the misinformed comments about whether or not to trust the service bulletins.

Oh great, agreed. I’m gonna follow their mandates in Service bulletins, makes reasonable sense.

It’s just seems some have stated to listen to the engineers in the Service Action bulletins. But now that it has changed/been updated they seem to ignore that stance now that it doesn’t follow their narrative.

[old///MFanatic]

I'm an original MY2006 owner - still. I'm not reading anything - I recall it clearly.
The way it worked and what new owners were told are as I originally wrote.

Just having a conversation, forgive me trying to clarify what you’re stating.
1)Are you saying your 2006 M3 was part of the free rod bearing Service Action (422) and you had it done?
2)Are you saying you have written notice that after the service action you had a mandated oil change within 1,200 miles after the rod bearing break-in?
Thank you.

[bigjae46]

I'd say you do need to do an oil change soon after disassembly and inspect the oil & filter or do an oil analysis. You'd probably want to go easy on it at first (break in) to make sure there is nothing wrong. Beyond that...not sure what you get by going easy on the motor.