I own a 2013 E92 M3 with 45,000 miles. I know the main bearings were an issue for this particular motor but have seen and heard some conflicting information. From what I understand there were a lot of failures early on but that the later model years used a different main bearing with less issues. The car is driven hard on occasion and I do four or five track days a year. Do you think I should have the main bearings replaced at this point as a precaution?
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Rod bearings. Do more research
Main bearings basically require a full engine rebuild. As others said do research it’s well documented. Rod Bearings.
To the OP's point, the main bearings are also very tight, too.
The main bearings are not really an issue on this platform. I am not saying it hasn’t happened but it is not likely. Rod bearings are a 100,000 mile maintenance in my opinion. Like someone already said I wouldn’t do mains unless the whole motor was getting an overhaul or there was a real reason to suspect them.
Disagree. If you look at the bearing wiki, you'll see the mains are also tight, too. I'm currently doing a rebuild because of failed mains.
RocketyMan wroteAnd the rod bearings were fine? Usually the spun rod bearing wrecks the crank and takes a main with it.Disagree. If you look at the bearing wiki, you'll see the mains are also tight, too. I'm currently doing a rebuild because of failed mains.
spammysammich wroteNope. Didn't say that neither. Both are a problem.And the rod bearings were fine? Usually the spun rod bearing wrecks the crank and takes a main with it.
RocketyMan wroteDisagree. If you look at the bearing wiki, you'll see the mains are also tight, too. I'm currently doing a rebuild because of failed mains.
Yeah pretty standard fare for S motors. My neighbor had a S54 on his engine stand every few months during track season and when he was trying to flip cars.
http://wiki.rcollins.org/core/index.php/Engine_Specs_-S65/S85_Main_Bearings
Thick oil certainly doesn't help with this whole ordeal. The mains need to ideally be looser, too, and they are tight with a nominal clearance of 1.6 thou from the factory. Just like with the rods, but the rods are worse with a nominal clearance of 1 thou.
Both are crap tight. Rods probably are the worst out of the two. An ideal world would have the mains and rods 2.5 thou...at least. But a spun bearing can certainly happen out of either.
Replacing the rod bearings with increased clearance (greater than factory "nominal") can help with [oil] flow, and seems to be the minimum with this engine.
To the OP's point about the "newer" bearing style...I think the aluminum-tin is worse. The lead-copper babbit seems to be more forgiving on accidental metal-to-metal contact with more "anti-seizure" resistance. But BMW went with the new bearing because of euro EPA Bolshevik about lead--or at least that's what's been projected as why.
Thick oil certainly doesn't help with this whole ordeal. The mains need to ideally be looser, too, and they are tight with a nominal clearance of 1.6 thou from the factory. Just like with the rods, but the rods are worse with a nominal clearance of 1 thou.
Both are crap tight. Rods probably are the worst out of the two. An ideal world would have the mains and rods 2.5 thou...at least. But a spun bearing can certainly happen out of either.
Replacing the rod bearings with increased clearance (greater than factory "nominal") can help with [oil] flow, and seems to be the minimum with this engine.
To the OP's point about the "newer" bearing style...I think the aluminum-tin is worse. The lead-copper babbit seems to be more forgiving on accidental metal-to-metal contact with more "anti-seizure" resistance. But BMW went with the new bearing because of euro EPA Bolshevik about lead--or at least that's what's been projected as why.
RocketyMan wroteHow many failures? Clearances being tight is something but there is no issue relatively close to the RB’s. Typically mains are not an issue for us. If your main are an issue there were other culprits ignored that caused it. I’ve not seen mains fail without ignored issues. To make these a thing to consider out of nowhere is nuts.Disagree. If you look at the bearing wiki, you'll see the mains are also tight, too. I'm currently doing a rebuild because of failed mains.
Scrippy wroteWhat other ignored culprits do you mean?How many failures? Clearances being tight is something but there is no issue relatively close to the RB’s. Typically mains are not an issue for us. If your main are an issue there were other culprits ignored that caused it. I’ve not seen mains fail without ignored issues. To make these a thing to consider out of nowhere is nuts.
Typically the RB clearance is the critical part because it can be potentially the tightest. So I agree that the con rods need to be looked at--at a minimum. But you cannot discount the mains as they are too tight as well.
Spun bearings on these engines is not exclusive to only the con rods. BOTH mains and con rods are tight. So BOTH can fail independent of another.
mains are also an issue but fixing it is much more involved than rod bearings, main bearings is basically complete engine removal and disassembly.
seems like there isn't a consensus of how much mileage until the rod bearings would break...
i've got 41k miles on my 2010 (pre-LCI) e92m3 and still debuting whether to upgrade the rod bearings now, or should I wait until 50k miles?
i've got 41k miles on my 2010 (pre-LCI) e92m3 and still debuting whether to upgrade the rod bearings now, or should I wait until 50k miles?
spammysammich wroteIt's the other way around that's more common in these engines, a failed main takes out the rod bearing after it. #1 main bearing comes first in the oil path. It's also the main bearing that has failed more commonly. #1 main bearing also has more forces / strain placed on it if a supercharger bolted to the front of the engine, there were a lot of main bearing failures due to that.And the rod bearings were fine? Usually the spun rod bearing wrecks the crank and takes a main with it.
There are still way less failures due to main bearings than rod bearings. Some rod bearing failures are actually misdiagnosed main bearing failures because they don't take the time to tear down the engine to see the actual root cause. Since it requires pretty much a rebuild, most deem it an acceptable risk since a replacement will likely run you close to the cost of a used motor or more if built with upgraded parts.
deansbimmer made a great step by step thread on main bearing replacement that is worth a read, or at very least a skim to understand the process.
evangelion139 wroteThat's because every engine is different. There is no set mileage where they fail.seems like there isn't a consensus of how much mileage until the rod bearings would break...
i've got 41k miles on my 2010 (pre-LCI) e92m3 and still debuting whether to upgrade the rod bearings now, or should I wait until 50k miles?
No one can tell you unless they take them apart or have a crystal ball. If you take it a part to inspect it, you might as well change them.
There have been failures under 10k miles, under 100k and failures past 100k miles. There is a thread and a list of failures you can take a look at.
tdott wroteYou mean cyl#5, right? Because the 1st main feeds con rod 5 since bank 2 is before bank 1.It's the other way around that's more common in these engines, a failed main takes out the rod bearing after it. Cyl#1 main bearing comes first in the oil path. It's also the main bearing that has failed more commonly. Cyl#1 main bearing also has more forces / strain placed on it if a supercharger bolted to the front of the engine, there were a lot of main bearing failures due to that.
There are still way less failures due to main bearings than rod bearings. Some rod bearing failures are actually misdiagnosed main bearing failures because they don't take the time to tear down the engine to see the actual root cause. Since it requires pretty much a rebuild, most deem it an acceptable risk since a replacement will likely run you close to the cost of a used motor or more if built with upgraded parts.
This is EXACTLY the issue I'm fixing right now with an S65 engine. The 1st main spun and I'm trying to get the main journal repaired.
RocketyMan wrotesorry meant #1 main bearing.You mean cyl#5, right? Because the 1st main feeds con rod 5 since bank 2 is before bank 1.
This is EXACTLY the issue I'm fixing right now with an S65 engine. The 1st main spun and I'm trying to get the main journal repaired.
tdott wroteYeah. I knew what you meant. But just for clarity, I don't think the others would've known what you meant.sorry meant #1 main bearing.
tdott wrotewhere is that? tried searching for it but didn't find it.. would be interested in reading up.
kolosy wrotehttps://www.m3post.com/forums/showthread.php?t=1504062where is that? tried searching for it but didn't find it.. would be interested in reading up.
