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

[terra]

Well, it wasn't a 20 year old car 20 years ago when I had the bearings done.

Yeah, but I doubt anyone who got it done back then is still working on reaching the break-in period.

In any case, the dealer actually wouldn't be able to tell by the DME since it only records the max RPM *ever* reached. It doesn't keep a continuous log or last X number of drives or anything like that. Very likely the car would have been red lined at least once before being brought in for a bearing changed.

[Slideways]

Yeah, but I doubt anyone who got it done back then is still working on reaching the break-in period.

In any case, the dealer actually wouldn't be able to tell by the DME since it only records the max RPM *ever* reached. It doesn't keep a continuous log or last X number of drives or anything like that. Very likely the car would have been red lined at least once before being brought in for a bearing changed.

Where is the max RPM logged on the DME? The service bulletin states, "reprogram DME control module" after rod bearing service is performed. There is also something about the SMG control module - http://www.siwilson.com/BMW/Service_...20Bulletin.pdf

[terra]

Where is the max RPM logged on the DME? The service bulletin states, "reprogram DME control module" after rod bearing service is performed. There is also something about the SMG control module - http://www.siwilson.com/BMW/Service_...20Bulletin.pdf

It’s not stored with the program/tune. Newer software may have had more aggressive knock control or something as a last ditch effort to protect the bearings.

[liam821]

When I'm breaking in the engine in my race car it's start the car on crappy oil, idle until operating temperature checking for leaks etc, change the oil to your oil of preference, strap it to a dyno and let it eat.

[mrgizmo04]

☝️full send 👍

[Mspir3d]

What's more important than break-in is proper install. Which is what I think individuals nerf when they have rod bearing failure after a replacement.

One of the local M3 owners posted this the other day. He had just bought the car and it was making a ticking sound but he thought it just needed a valve adjustment. Now the block is well ventilated with a total of 5 windows. It looks like someone messed up the rod bearing replacement.

[mrgizmo04]

One of the local M3 owners posted this the other day. He had just bought the car and it was making a ticking sound but he thought it just needed a valve adjustment. Now the block is well ventilated with a total of 5 windows. It looks like someone messed up the rod bearing replacement.

That sucks. Did he post on facebook that he had a ticking noise, got responses that "it's normal", to which he said, "thanks, sending it"...?

[oceansize]

Just what I wanted to see before I do mine. Gulp....

[mrgizmo04]

My take on the TSB comments.

Remember this was written during the chaos around 2003-2004 when they had to do a recall on all cars because the original clearances they engineered were too tight, and did not provide enough of an oil lubrication layer so the bearing shell rode on the cranks a lot resulting in friction/heat/etc and caused the problems at the oil pressure the system could produce and maintain. The bandaid solution that they came up with so they would not lose much $ on at the time, was to increase oil viscosity (I believe they started on these engines at 5-30 and because of this they switched to 10-60), along with making the bearing clearances a bit larger. I think someone in corporate and legal said - better safe than sorry, we know these guys like to go 8k all day, we can't keep replacing these things indefinitely, so let's get them out of our hair for at least 1.2k miles, tell them to use half the rpm range and see if it works. It kinda did. Proper way to do it would be to redesign the crank/bearing/rod width and make the system into a dry sump with higher pressure, but that would be catastrophic in terms of time and cost and then rebuilding every engine.

The 10-60 oil is a bit of a catch 22. It is super thick when the car is cold (think of honey or molasses trying cover and roll on the spoon, basically exact analogy) and that increases resistance to being pumped everywhere it needs to go and that decreases the pressure. However the oil needs to be this thick in order to keep up (best it can) with proper lubrication at high rpm at the pressure the pump is able to generate and maintain when the car is being beat on and the temps climb.

The summary is - I'm not sure how much I trust engineers or corporate or lawyers who originally designed something incorrectly and put a band aid fix on it (and all the other fun areas on this car like vanos and subframes and diff clutch - they just can't seem to get clearances and tolerances right 😁 including the subframe body cavity). Take it easy on the car when it is cold and start opening it up only when the OIL temp gets up to operating, NOT the coolant (which I think most folks use as the indicator for when to start sending it). If you do send it a lot once it is up to temp, just reduce your oci and give it fresh oil more frequently. Also keep an eye on oil levels - higher mileage cars that might burn some or leak. Treat the bearings as a maintenance item every ~75k miles. I will not get into Blackstone tests in this thread .

[Obioban]

My take on the TSB comments.

Remember this was written during the chaos around 2003-2004 when they had to do a recall on all cars because the original clearances they engineered were too tight, and did not provide enough of an oil lubrication layer so the bearing shell rode on the cranks a lot resulting in friction/heat/etc and caused the problems at the oil pressure the system could produce and maintain. The bandaid solution that they came up with so they would not lose much $ on at the time, was to increase oil viscosity (I believe they started on these engines at 5-30 and because of this they switched to 10-60), along with making the bearing clearances a bit larger. I think someone in corporate and legal said - better safe than sorry, we know these guys like to go 8k all day, we can't keep replacing these things indefinitely, so let's get them out of our hair for at least 1.2k miles, tell them to use half the rpm range and see if it works. It kinda did. Proper way to do it would be to redesign the crank/bearing/rod width and make the system into a dry sump with higher pressure, but that would be catastrophic in terms of time and cost and then rebuilding every engine.

Incorrect on several counts:
-They were never specced too tight-- that was the s65 and s85. S54 bearings follow conventional engine design theory on bearing clearances
-the spec didn't change. The original batch of bearing were manufactured incorrectly. The bearings that replaced them were built to the original spec, just the this time they were made correctly.
-if they had been too tight, going to a thicker oil would have exacerbated the situation
-the engine was originally designed for 10w-60. We had (m3forum) testimony to that effect from the guy that led the oil team. 5-30 was a last minute change by the marketing team to make it seem like they were easy to maintain cars. When bearings were spinning, the engineers got their way finally.

[mrgizmo04]

Incorrect on several counts:
-They were never specced too tight-- that was the s65 and s85. S54 bearings follow conventional engine design theory on bearing clearances
-the spec didn't change. The original batch of bearing were manufactured incorrectly. The bearings that replaced them were built to the original spec, just thing time they were made correctly.
-if they had been too tight, going to a thicker oil would have exacerbated the situation
-the engine was originally designed for 10w-60. We had (m3forum) testimony to that effect from the guy that led the oil team. 5-30 was a last minute change by the marketing team to make it seem like they were easy to maintain cars. When bearings were spinning, the engineers got their way finally.

What does "manufactured incorrectly" mean? I guess they could not have been any narrower before (lol), so my guess is that they were too tight. Narrow = width they take up on the crank, not the thickness of the shell that increases/decreases the space between the rod and the crank. When I say tight/loose I am talking about thickness - space it takes up between rod and crank. Were they manufactured too long resulting in ovaling once the rod cap was torqued?

Once they started manufacturing them correctly (looser) it started making sense with the oil.

I'm happy to learn facts, my spiel is based on prior readings and research years ago about what engine builders like Lang and others thought on the subject specific to S54.

[IamFODI]

FWIW, I recently came across a PDF from Glyco (attached) that has this nugget on page 10:

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.

I don't know what "minimal" means in this context, so I can't say how widely applicable this, but... does this count as break-in? Looks like it to me. Maybe it's only for some applications.


Side note: I do know Andre is wrong on ZDDP in engine oils. Many modern oil standards have imposed limits on phosphorus and/or other chemical properties (e.g. ash formation) that force a reduction of ZDDP content, but it hasn't been eliminated entirely from car engine oils. Also, modern forms of ZDDP are more effective and there are other anti-wear chemistries available, so it's not necessarily a given that modern oils have poor anti-wear performance.

[Jimbo's M]

Remember this was written during the chaos around 2003-2004 .

It was earlier than that. The very first year model was suspect, then the 'service action', it was never a 'recall', started. My car is a 12/01 build, and just months later it was in getting new bearings. Then it was determined that that batch was bad as well. In again I went. By ~4/02 builds they figured they got it right. I guess so, I've been on these since then.

[Arith2]

I wouldn't doubt a TSB over the chaos in 2003-2004. There is simply not even wear on bearings. The rods are not moving in a perfect circle. They push at certain points and have no load at others in the same 180°. Heck, they even move sideways sometimes. My previous bearings are clear evidence of that. Theory is nice but in reality, the TSB is solid advice. If you have a race engine, 1200 miles is absolutely unreasonable. Idle it for a bit and send it. It's a race engine and something will probably fail before something as robust as the bearings.

Our M3s are not dedicated track cars. We want longevity out of them. BMW isn't sponsoring us new engines and we are invested in our vehicles. Don't write off something that can determine whether your bearings last 50k miles or 150k. They absolutely do it. Some spin bearings long before that. Like me at 71k.

I'm pretty annoying that a simple disregard of physics is happening. Engine theory says bearings don't wear because rods never touch. Bs.

[jbfrancis3]

TSBs are written by engineers. The rod bearing TSB says a break in period is required after replacing rod bearings.

Corporate training materials are the final forms they take, regardless of special names or special audiences. Sure, the content may originate from engineers tasked with fixing an issue. But a stream of conscious engineering thought does not land on a piece of paper and get broadcasted to dealerships worldwide. My point is everything goes through various checkpoints, as with anything in Corporatia. In this example, if engineers were truly left to their own devices? There would be steps to measures clearances, and no MPH spec because that means nothing.

I have nothing to gain here. I said there is not a need; I did not say don't follow them. It is good idea to follow all TSBs and associated procedures. It was helpful for someone to post the TSB itself so others searching can see the resources so thanks.

But I am biased towards my own thoughts, crazy as that may sound. I'd rather discover a clearance issue immediately than float through suspended reality for 1,500 miles...