Brintech Main Bearing Failure Discussion

[oceansize]

Interesting tear down and discussion on S65 main bearings and the potential for failure from Brintech. Nicely done and straight to the point.

[Slideways]

I have heard this theory about the timing chain pulling the crank enough to wear out the first main bearing. I would think that some upper bearing wear should also be happening to bearings two and three since the entire crank is being pulled at one angle. All I know is replacing main bearings on the S65 is an engine out service due to the use of a bedplate. I thought that you could roll the main bearings in, which is possible on an engine with main caps.

IDK, higher mileage S65s can have main bearing issues and the S54s can have headgasket issues. Headgasket can be done in car, so S54 FTW hah

[IamFODI]

Interesting ideas. And Brintech seems like a good shop.

I still have questions, and they're pretty much the same questions I have every time a couple of guys talk like they've used garage tools and moxy to outperform one of the most competent and best-equipped engine builders in the world.

What percentage of S65s actually have this issue? There are tens of thousands of these engines all over the world, and they've been doing real miles for years. With numbers like that, there's always gonna be a story every once in a while where some shop somewhere happens to have several engines come in in quick succession with the same failure mode. It's bound to happen by chance alone, even if you ignore the fact that shops like this are disproportionately likely to see catastrophic failures. And now that shops can post about this stuff on platforms like YouTube, whose algorithms will make sure we see it, we're likely to hear about it. Maybe it's indicative of a trend with this engine, or maybe it's a fluke. There's no way to know just from one shop saying they've seen five engines like this and a smattering of other anecdotes.

What are the histories of the engines that have had this issue? They're talking about this like it threatens all S65s, but do we know for sure it isn't affected or determined by usage patterns, fuel, etc.? Sounds like they either don't know or don't want to share.

Even if we buy the idea that the no. 1 main is worth worrying about like the OG rod bearings were, how do we know the best fix is to mess with the bearing, never mind boring out that hole in the block and adding a sleeve? Do we know for sure that fixes the problem? Do we know for sure the process has no side effects? Looks like Brintech doesn't. All they say is "it's working well", which is vague enough to be almost meaningless. And that part about the oil hole mod, where the guy basically says he's pretty sure it'll be okay... Woof.

I guess I can't speak for everyone, but I need a much higher standard of evidence before I let someone disassemble and cut on my engine.

I'll be watching this space, especially because the stakes seem high if Brintech is right about this. For now, I don't buy any of it.

[Slideways]

Interesting ideas. And Brintech seems like a good shop.

I still have questions, and they're pretty much the same questions I have every time a couple of guys talk like they've used garage tools and moxy to outperform one of the most competent and best-equipped engine builders in the world.

What percentage of S65s actually have this issue? There are tens of thousands of these engines all over the world, and they've been doing real miles for years. With numbers like that, there's always gonna be a story every once in a while where some shop somewhere happens to have several engines come in in quick succession with the same failure mode. It's bound to happen by chance alone, even if you ignore the fact that shops like this are disproportionately likely to see catastrophic failures. And now that shops can post about this stuff on platforms like YouTube, whose algorithms will make sure we see it, we're likely to hear about it. Maybe it's indicative of a trend with this engine, or maybe it's a fluke. There's no way to know just from one shop saying they've seen five engines like this.

What are the histories of the engines that have had this issue? They're talking about this like it threatens all S65s, but do we know for sure it isn't affected or determined by usage patterns, fuel, etc.? Sounds like they either don't know or don't want to share.

Without answers to those two questions, I don't see any evidence that I or any other individual S65 owner has to worry about their main bearings in the first place.

Even if we buy the idea that the no. 1 main is worth worrying about like the OG rod bearings were, how do we know the best fix is to mess with the bearing, never mind boring out that hole in the block and adding a sleeve? Do we know for sure that fixes the problem? Do we know for sure the process has no side effects? Looks like Brintech doesn't even know. All they say is "it's working well", which is vague enough to be almost meaningless. And that part about the oil hole mod, where the guy basically says he's pretty sure it won't have any bad side effects... Woof.

I guess I can't speak for everyone, but I need a much higher standard of evidence before I let someone disassemble and cut on my engine.

I'll be watching this space, especially because the stakes seem high if they're right. For now, I don't buy it.

There are a few examples with this main bearing failure. Even if it is or is not a thing, you just have to run the engine as long as it will go. All you can do is warm up properly and change the oil. If the engine lets go, BMW made about 66,000 of them, so there will donor engine somewhere.

Knowing that the main bearings can go, it almost makes you not want to do the rod bearings lol. Speed Academy did the rod bearings on a higher mileage S65 only to have a main bearing failure less than 4000 miles later.

[IamFODI]

There are a few examples with this main bearing failure.

Yeah, I've seen some as well. What's unclear to me is whether it's worth thinking about them as connected or just part of the typical background noise of occasional engine failures.

Even if it is or is not a thing, you just have to run the engine as long as it will go. All you can do is warm up properly and change the oil. If the engine lets go, BMW made about 66,000 of them, so there will donor engine somewhere.

Agreed.

Knowing that the main bearings can go, it almost makes you not want to do the rod bearings lol. Speed Academy did the rod bearings on a higher mileage S65 only to have a main bearing failure less than 4000 miles later.

Rod bearing service followed by main bearing failure seems to be a recurring story with this engine, too. Understandable IMO; every time you open your engine is an opportunity to mess something up (e.g. by introducing debris that accelerates wear somewhere else). Yet another reason to be careful when listening to people who say you need to open up your engine right now and do XYZ to fix a problem.

There's a series of videos on YouTube – not linking publicly because they're obvious clickbait trash – where this guy knowingly buys a clapped-out E9x M3 that's making bad engine noises, does a super slap-dash rod bearing job (amazing what people are willing to put out videos of themselves doing), and drives it despite it still making bad noises. It blows up almost immediately – like a few miles up the road. What's his conclusion? S65s are unreliable.

And remember that failed class action lawsuit against BMW for S65/S85 rod bearings? IIRC one of the reasons it was rejected was that both cars held up as representatives of the class were found to have had mods and/or bad maintenance records and/or documentation of an overrev or something. Probably says something that there's never been a successful effort to muster examples that would hold up in court.

These engines definitely have their weaknesses, but also people definitely treat them poorly and either don't know or pretend they didn't, so it's hard to know what's real.

[George Hill]

I just bought an S65 that was locked up. I assumed it had a spun main, but has a spun rod bearing instead. I pulled the oil pump and can see the #1 main has not turned. I'll have it a part to address the crank/rod and will be curious to see the condition of the #1 main bearings.

I agree that this IS an issue, but I also think that it is still so small in quantity that its hard to justify worrying about for the vast majority of owners if they are treating the engines properly.

[bigjae46]

There was a theory that supercharging would accelerate main bearing wear because of the increased tension on the crank.

Many high mileage examples with no main issues, not sure it will keep me up at night. But this is why I love being the original owner of my car, I know its been treated right. I'm sure more people will run into this issue as they buy examples that were allegedly maintained.

I'm about to retire my E90 from daily duty. It will be awhile but I planned to change out the mains somewhere between 150k to 200k more out of curiosity.