Aftermarket Rod Bearings Spun

pbonsalb wrote

I am just a DIYer, but I don’t think this job is rocket science. It just requires care, patience, and attention to detail. What is the pro going to do differently than me?

You won't necessarily know until later. The amateur's job may not blow up right after first start, but not every mistake is made known immediately. That is the key takeaway here.

Like, 10k miles later when your oil pan starts to leak because you couldn't quite clean the surfaces well enough. Or 40k miles later because the upper shells weren't installed as well as if you had better access...

Or as is the case with one of my customers- Another "pro" shop missed a minor detail by installing a bearing backwards and sent it out the door. Because they did the job with a subframe in their face the whole time.. It ran fine for 200 miles before knocking. They're now on the hook to pay for our work rebuilding that engine. ($16k)

deansbimmer wrote

You won't necessarily know until later. The amateur's job may not blow up right after first start, but not every mistake is made known immediately. That is the key takeaway here.

Like, 10k miles later when your oil pan starts to leak because you couldn't quite clean the surfaces well enough. Or 40k miles later because the upper shells weren't installed as well as if you had better access...

Or as is the case with one of my customers- Another "pro" shop missed a minor detail by installing a bearing backwards and sent it out the door. Because they did the job with a subframe in their face the whole time.. It ran fine for 200 miles before knocking. They're now on the hook to pay for our work rebuilding that engine. ($16k)

Another thing to keep in mind...its only 4 bolts.

deansbimmer wrote

Another "pro" shop missed a minor detail by installing a bearing backwards and sent it out the door.

I like DIYing, and apparently did my bearings better than at least one pro shop.

I think it's pretty obvious pro or not, what matters most is cleanliness and attention to detail as well as taking your time and doing things right.

A busy shop environment, rushing to get it done because you only get paid X hrs per job (flat rate mechanics), working on several cars at the same time, switching between, answering customer phone calls, talking to walk in customers, starting and stopping etc etc. are distractions that can lead to mistakes.

IMO it's important to avoid distractions and focus on the job at hand, and have attention to detail, that is something most shops are not good at doing PERIOD.

deansbimmer wrote

Plenty have confirmed that you can do the job without, but not removing the subframe is cutting corners. Period. You simply can't employ the same degree of cleanliness and attention to detail with it dangling. Mistakes can be made more easily (as evidenced in my last post).

Why stop there, isn't it cutting corners if you don't take the motor out and turn it over on an engine stand so you can have even more access?

tdott wrote

I think it's pretty obvious pro or not, what matters most is cleanliness and attention to detail as well as taking your time and doing things right.

A busy shop environment, rushing to get it done because you only get paid X hrs per job (flat rate mechanics), working on several cars at the same time, switching between, answering customer phone calls, talking to walk in customers, starting and stopping etc etc. are distractions that can lead to mistakes.

IMO it's important to avoid distractions and focus on the job at hand, and have attention to detail, that is something most shops are not good a doing PERIOD.



Why stop there, isn't it cutting corners if you don't take the motor out and turn it over on an engine stand so you can have even more access?

For this reason I've always thought it's important to only do what's necessary to a car (not debating the necessity of RBs). Every time a tech does a complicated procedure, especially for other preventative stuff, you're introducing the possibility that they make a mistake and potentially harm the car. Doesn't matter if it's a BMW dealership, independent, etc. Mistakes happen.

It's why I shy away from preventative stuff other than things that can cause catastrophic failure. I can't count the number of times I have done work and have had leftover bolts or clips, or gotten a car back from a legitimately good shop and found a bolt missing.

tdott wrote

Why stop there, isn't it cutting corners if you don't take the motor out and turn it over on an engine stand so you can have even more access?

Oh sure, but why not just rebuild the whole engine too!

I agree that many shop environments are as you describe, and we absolutely acknowledge it. We aren't and that's a huge selling point to our customers. I can't recall having a come back of any kind. We approach jobs with a critical mindset, and there are others out there like us too.

Preventative maintenance is a good thing. MANY critical industries operate on that premise. Indeed, not every auto shop is up to it. However, there are many other good shops out there fighting to overcome the same mindset with their customers. Sadly, not everyone has access to these truly good shops- it's too bad for the car, and unfortunately sticks the good shops with the same stigma.

tdott wrote

Why stop there, isn't it cutting corners if you don't take the motor out and turn it over on an engine stand so you can have even more access?

One could argue that access is not improved as once the sub-frame is out of the way, you have full access to the engine - it is just above you.

And it may be said, by a cheeky bastard like me, that it is actually better to have the engine above you as gravity will drop particulates down and out of the engine instead of into the cylinders...

All kidding aside, it is about minimizing risk. Dropping the sub-frame does not introduce substantial risk as it is simple and pretty hard to screw that process up or break something given it is mostly robust. Other than a few small electrical connectors, most stuff is big, bulky and forgiving. The reward is unfettered access to the engine's bottom end.

While removing the engine may marginally reduce some risk, such as better lighting or working position, the removal and re-installation process is rife with risk as there are many things that can be damaged or improperly removed/installed.

I certainly wish more shops offered the level of care and support that shops like Deansbimmer offer. Sometimes, we owners are our own worst enemies. Expecting perfection while demanding the cheapest price allows shops that cut corners to stay in business. Competition is good, but make sure to compare apples to apples!

I digress.

And so, I wonder if the op ever stripped down his engine to see if the No1 mains had failed?
I'm guessing not as the whole engine is for sale.

Hello op? (I see you're still active here).

Assimilator1 wrote

And so, I wonder if the op ever stripped down his engine to see if the No1 mains had failed?
I'm guessing not as the whole engine is for sale.

You're correct. Haven't done more then dropped the pan.

"previous owner said he did all maintenance at BMWs recommendations"

not necessarily comforting

Excers wrote

You're correct. Haven't done more then dropped the pan.

Ok, thanks for the update (maybe if you sell it, the buyer would strip it & LYK what happened to it?? If so, could you let us know?).

Assimilator1 wrote

Excers wrote

You're correct. Haven't done more then dropped the pan.

Ok, thanks for the update (maybe if you sell it, the buyer would strip it & LYK what happened to it?? If so, could you let us know?).

I will keep you updated.

North.E92 wrote

this thread makes me glad im in cali and theres actually a lot of reputable shops here who pride themselves on regularly doing rod bearing jobs for M3's. gives me peace of mind and also makes pricing more competitive lol.

Mine were installed by the pretty much most reputable shop in the area. You can still spin a bearing lol.

The few times that replaced rod bearings have failed, it has been a main bearing that failed that caused the replaced bearings to fail. If anyone knows of cases in which replaced rod bearings have failed and the main bearings have been fine, post the details. It is certainly possible that someone could install rod bearings incorrectly and cause a failure, but I think at most there has been one example and can't remember the details so I am not even sure about the one.

There are a few people who suggest not changing rod bearings as preventative maintenance because it is just an opportunity for a mechanic to screw up your car, but people like that are in the minority and mechanics who screw up your car are also few and far between. They do exist. I started DIYing years ago to save money and have not used a shop in years. I did my own rod bearings in 2014, about 40k miles ago. There is now a good DIY by SYT_Shadow if you feel confident enough to do it or have a friend who knows more who would help. I had a mechanic friend stop by for the first set I did and then I helped someone else local do theirs a year later.

pbonsalb wrote

The few times that replaced rod bearings have failed, it has been a main bearing that failed that caused the replaced bearings to fail. If anyone knows of cases in which replaced rod bearings have failed and the main bearings have been fine, post the details. It is certainly possible that someone could install rod bearings incorrectly and cause a failure, but I think at most there has been one example and can't remember the details so I am not even sure about the one.

There are a few people who suggest not changing rod bearings as preventative maintenance because it is just an opportunity for a mechanic to screw up your car, but people like that are in the minority and mechanics who screw up your car are also few and far between. They do exist. I started DIYing years ago to save money and have not used a shop in years. I did my own rod bearings in 2014, about 40k miles ago. There is now a good DIY by SYT_Shadow if you feel confident enough to do it or have a friend who knows more who would help. I had a mechanic friend stop by for the first set I did and then I helped someone else local do theirs a year later.

Yes I would be interested to know about the main bearing as well. I went ahead and did bearings myself after the swap and haven't had any issues.

330indy wrote

"previous owner said he did all maintenance at BMWs recommendations"

not necessarily comforting

He took amazing care or the car overall but yes so much unknown without all the service records. He definitely could have went long on some oil changes.

TheRussski wrote

TrAcK TRaP wrote

No its not. Thanks for asking. Another 65.700 E9X's still drives fine without problem. RB's fails on even ford expeditions and other vehicles so there is of course chance but less than you could imagine.

We don't know how many of those 65.700 failed prematurely. Check out bearing change example thread where most bearings come out with LOTS of wear and many of them are on their final layer....you can't argue with proven picture evidence

IamFODI wrote

TheRussski wrote

We don't know how many of those 65.700 failed prematurely. Check out bearing change example thread where most bearings come out with LOTS of wear and many of them are on their final layer....you can't argue with proven picture evidence

TrAcK TRaP wrote

Which they say same thing for 50K, 60K, 80K, 100K, 130K miles vehicle. Between first and last number there is another 80K miles or 6-8 years of driving. Check other post here that guy just purchased a car w/170K miles. If you ask me RB,s of course has a wear on that car just like we say same thing for 50K miles car and most of you guys thinks it will fail very soon.

If there's a lesson from the bearing condition thread, it's not that most S65s will grenade from rod bearing failure. It's that rod bearings are enough of a problem in this engine that owners should be mindful of it.

I actually agree that the probability of an actual failure per se -- i.e. spinning a bearing, chewing the crank, etc. -- doesn't seem too high. Taking that "close to 200 members" number at face value (I haven't counted and don't care to), the real number would have to be >3x that to equal 1% of all E9x M3s sold.

I also get the impression that most people overestimate the failure rate because they conflate excess wear with failure.

However, given the time and expense involved in rebuilding one of these engines, it still make sense to assume your rod bearings will wear excessively, and that you should change them preventatively to reduce the risk of a failure.

So really, you're both right.

Whaddya say we get back to speculating wildly about what's wrong with OP's engine?

Technically speaking from engineering terminology, a part is considered to have "failed" once it wears out of spec. This means that many bearings fail. Pretty much every one taken out of a car shows excessive out of spec wear therefore meaning the bearings have failed.

Now that doesn't mean that every failed bearing causes the engine to fail. While a bearings might have excessive wear and considered to be "failed" it generally requires much more wear until we see engine failure or other parts start to fail because of it. Example being a spun bearing marring or scoring the crank or a seized bearing throwing a rod.

Joshbot007 wrote

Pretty much every one taken out of a car shows excessive out of spec wear therefore meaning the bearings have failed.

Definitely true of 088/089 bearings. I'm not so sure it's true of 702/703 bearings.

702/703 bearings definitely look worn when they're pulled, but unlike with traditional lead/copper bearings, we don't really have a reference for how their appearance correlates with wear because we don't really know what kind of bearing they are. It was thought for the longest time that they were bimetal aluminum because that's what BE had posted, but that turned out not to be true. They updated their info after that revelation, supposedly after calling Glyco; now they call it a "trimetal" bearing, but that doesn't say much and they don't seem to be in a hurry to share any further info.

Also, I found a Glyco PDF (attached) that suggests that some amount of surface wear on a bearing with very tight clearance is normal and beneficial:

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.

When I read this I can't help but recall the fact that even very low-mileage 702/703 bearings show the same wear pattern. If that appearance correlated cleanly with actual wear, like how seeing copper on the old bearings did, why aren't engines with the new bearings throwing rods all day?

Not saying there's nothing wrong with 702/703 bearings, but I feel like there has to be more to the story than "looks worn = is worn out of spec".

IamFODI wrote

Joshbot007 wrote

Pretty much every one taken out of a car shows excessive out of spec wear therefore meaning the bearings have failed.

Definitely true of 088/089 bearings. I'm not so sure it's true of 702/703 bearings.

702/703 bearings definitely look worn when they're pulled, but unlike with traditional lead/copper bearings, we don't really have a reference for how their appearance correlates with wear because we don't really know what kind of bearing they are. It was thought for the longest time that they were bimetal aluminum because that's what BE had posted, but that turned out not to be true. They updated their info after that revelation, supposedly after calling Glyco; now they call it a "trimetal" bearing, but that doesn't say much and they don't seem to be in a hurry to share any further info.

Also, I found a Glyco PDF (attached) that suggests that some amount of surface wear on a bearing with very tight clearance is normal and beneficial:

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.

When I read this I can't help but recall the fact that even very low-mileage 702/703 bearings show the same wear pattern. If that appearance correlated cleanly with actual wear, like how seeing copper on the old bearings did, why aren't engines with the new bearings throwing rods all day?

Not saying there's nothing wrong with 702/703 bearings, but I feel like there has to be more to the story than "looks worn = is worn out of spec".

There definitely is something more, something (not just bearings) can appear visually worn but in fact still be within specifications. A bearing would have to be measured, not just in the depth of the wear, to determine if it is indeed truly out of spec. Bearings like these would very likely have other dimension constraints attached to them such as a surface deviation tolerance, concentricity, roughness, and more.

However, due to the theory that hydrodynamic bearings should see little to no wear due to there being a layer of oil between the crank and the bearing, even if we can't tell what "layer" the wear has broke due to being a different type. On the updated bearings we can still see wear we just cant visually gauge the depth.

I do not know the specifications for these bearings but if I were to bet I would say that any significant visual scoring, marring, scratching, loss of depth would violate a tolerance specification therefore labeling the bearings as "failed"

Failed doesn't mean non operational, the engineering term of failure generally means out of spec wear, or plastic deformation and just that. Plenty of parts on cars or anything else in this world continue to go strong even though by definition they have "failed"

Joshbot007 wrote

However, due to the theory that hydrodynamic bearings should see little to no wear due to there being a layer of oil between the crank and the bearing, even if we can't tell what "layer" the wear has broke due to being a different type.

Okay but...

1. How do we know the discoloration on 702/703 bearings really represents breaking through one important layer to another vs. some other mechanism (e.g. tribochemical) that turns out to be benign? Maybe sometimes it's one thing and sometimes it's another. Could we tell the difference just by looking at the kinds of pics people post?

2. To the extent that we really are seeing wear, how do we know whether it's different from the beneficial effects that Glyco describes in the excerpt I posted?

3. Given that we've seen this discoloration on very low mileage bearings, how do we know it's not just some break-in-like process that happens quickly and then doesn't progress much over the life of the bearing?

Thanks for the pdf linked, useful info

2. To the extent that we really are seeing wear, how do we know whether it's different from the beneficial effects that Glyco describes in the excerpt I posted?

Photos in the pdf by Glyco would've been a start, sadly I see they don't have any relating to that issue .

Re those later bearings, I would say that less of them appear badly worn vs the coppers ones, although I recall that Deansbimmer said on at least one occasion on one's he's replaced that some of them looked alright but felt really rough, obviously not good .

Assimilator1 wrote

Photos in the pdf by Glyco would've been a start, sadly I see they don't have any relating to that issue .

Not to mention the pics would have to be of the same type of bearings, which is an unknown to us at this point.

Some months ago, I did collect some example pics of 702/703 bearings from the bearing condition example thread and email them to someone at Glyco for comment. He said he couldn't tell for sure but "would guess" they show normal wear. I wouldn't take that as conclusive in any way, but I do think it's yet another reason not to take for granted that discoloration equals out-of-spec wear for 702/703 bearings.

The real arbiter would be measurements. That'd shut things down pretty quickly, one way or another.