Official S65 Rod Bearing Condition Example Thread

AHall wrote

Do the bearings have to be replaced every 50-60k miles after the first replacement? Is the problem poor bearings or an engine prone to excessive bearing wear?

deansbimmer wrote

There is no long term concern with BE or any other replacement rod bearing with the proper clearances. It's considered a one-time need. The main bearings in the engine will fail before new rod bearings will.

Why do the motors Blow with rod bearing failure?

BMW designed the S65 and S85 with approximately half the industry standard oil clearance. This is a trendy move among some auto manufacturers to increase gas mileage and increase horsepower. But when they do it, like in the Toyota Prius, the auto manufacturer also specifies a very thin oil to match the very small oil clearance. BMW dropped the ball here and is using very small oil clearance and very thick 10W60 oil. Many consider this its own recipe for disaster. But here's what is believed to be happening in the S65 and S85 engines.

Engines with clearance too small, couple with oil too thick, leads to premature rod-bearing related engine failures. With clearance too small and oil too thick, the lubrication around the bearing is marginal. Some metal-to-metal contact is made between the bearings and rod journal. The oil and rod bearings overheat. Some bearings seize on the crankshaft, while others will "spin" and cause a crankshaft failure. Here's the recipe how it can happen.

Tolerance Stacking

Every manufactured part has a manufacturing tolerance range that goes along with it. The parts are supposed to match the specification, but manufacturing variances will lead to these tolerance differences. When one part is on its outside tolerance, it's probably no big deal. When two parts are at the opposite of their tolerance limits, it can lead to catastophic failure as I will show.

Oil clearance is affected by three different parts, each having their own tolerance. Each of these specifications and tolerances were either specified by BMW, or measured in the field using multiple example components to build a database of component tolerance.

Connecting rod big end bore: 2.20474 [-0.00000, +0.00050] inch. That means the connecting rod big end can vary between 2.2047 - 2.2052. Nominal size would be 2.2049 inch.
Crankshaft connecting rod journal: 2.20465 [-0.00010, +0.00030] inch. That means the connecting rod journal diameter can vary between 2.0464 - 2.0468 inch.
Connecting rod bearing: 0.07850 [-.00015, +0.00015] inch. That means the connecting rod bearing thickness can vary between 0.07835 - 0.07865 inch.

The bearing clearance is calculated as the difference between the (connecting rod big end bore, two times the bearing thickness, and the connecting rod journal diameter. This is typically measured with a bore gauge when the bearings are assembled in the connecting rod, and size of the connecting rod journal is subtracted from the value found on the bore gauge.

omitted - look at measurements in original link

At miniumum stack up, the S65/S85 engine will last a very long time, even using the very thick 10W60 oil specified by BMW.

It is believed at maximum stack up, coupled with thick 10W60 oil leads to premature engine failures. These are the engines believed to blow with 25000 miles or less. A few engines have blow with 6000 miles or less; and one engine blew with only 1500 miles. The solution to this problem is increased bearing clearance.

Obioban wrote

... but, by increasing the clearance at the rod bearings, you're reducing oil pressure at the main bearings, potentially causing them to fail sooner. So, while the rod bearing life is increased by increasing clearance, engine life may not be-- and the part that is now failing is much harder to replace periodically (main bearing replacement is an engine out job).

After much deliberation, I put new OE (updated) rod bearings in my s85. Replacing them is an afternoon job-- like my S54, I will just do that on an interval I feel comfortable with. Too much potential risk associated with increasing their clearance, IMO.

serranot wrote

Theoretically, maybe, but BE also posted the oil pressure with their bearings, and it drops about 3 psi at the most, not really a concern. The oil pump can compensate to some degree for the increased clearance.

All things considered, there have been no reports of main bearing failure as a consequence of this issue but plenty due to rod bearing failures. I disagree with your risk assessment but to each his/her own.

AHall wrote

Could this not have been addressed by using a thinner oil to compensate for the smaller clearance?

Obioban wrote

... but, by increasing the clearance at the rod bearings, you're reducing oil pressure at the main bearings, potentially causing them to fail sooner. So, while the rod bearing life is increased by increasing clearance, engine life may not be-- and the part that is now failing is much harder to replace periodically (main bearing replacement is an engine out job).

After much deliberation, I put new OE (updated) rod bearings in my s85. Replacing them is an afternoon job-- like my S54, I will just do that on an interval I feel comfortable with. Too much potential risk associated with increasing their clearance, IMO.

Obioban wrote

I don't agree with this statement-- if you look at threads with main bearing failure, a shockingly large proportion of them have increased clearance rod bearings. IMO disproportionately many to the quantity of cars running increased clearance rod bearings.

The measured 4% pressure loss was before the bearings. As pointed out by IamFODI earlier in the thread, "we should remember that, for the aforementioned reasons, this means a pressure loss of at least that much everywhere else in the system – likely more at the source of the pressure loss (i.e. the rod bearings) and adjacent parts (e.g. the mains)."

If nothing else, if increasing the clearance addressed the issue without consequence, why would BMW have not updated the factory parts by now? Super easy fix, and BMW does rolling fixes to address failure modes all the time, including after cars go out of production.

Green-Eggs wrote

Here's the most simple advice we give people. If you don't believe there's a bearing clearance problem, then don't change your bearings...PERIOD. If you do believe there's a bearing clearance problem, then do change your bearings, but DON'T use OEM clearance bearings or any aftermarket bearing with OEM clearances.

Green-Eggs wrote

here's the data I want to see:
1. Collect all of the data for main bearing failures without rod bearings replaced.
2. Collect all of the data for main bearing failures with rod bearings replaced.
3. Remove all instances of supercharged engines.
4. Show us the data.

Green-Eggs wrote

That's been asked and answered dozens of times. Once BMW redesigns the bearings with increased clearance, that will be tantamount to admitting guilt and will trigger a class-action lawsuit that they will certainly lose as a result. In addition to damages BMW would have to pay, they would be forced to do a recall and fix every S65/S85 ever made. At $5500 cost per vehicle (probably a reasonable estimate), that would cost BMW nearly $700-million dollars. It would be far, FAR cheaper for BMW to get sued by every 500th car owner and be forced to fix the engine. So the answer really is as simple as that.

Obioban wrote

S54s use traditional bearing clearances-- just like BE does on their increased clearance S65/S85 bearings. Are you saying S54 owners shouldn't change their rod bearings? By your logic, no bearing clearance issue, therefore no reason to change them.

If so, that would be misguided-- engine failure would result.

I don't have the ability to collect that data. None of us do. The sample size on the forum is small and skewed/non representative.

If that's your criteria to move off aftermarket parts to stock parts (backwards logic, IMO), nothing is possibly going to compel you.

B.S.

BMW redesigns parts ALL the time to address failure modes, including after production ends. All car companies do. All companies that make physical products do.

As an example, the s54 vanos high pressure oil line fatigues under motion, causing it to crack and spray oil on the engine-- sometimes resulting in fire.

BMW addressed it after e46 M3 production ended, with no recall, by adding an additional fixation point. If you buy that part today, it's no longer an issue. This is something that could literally set cars on fire, and they changed it with no recall. The recall cost would also be quite cheap-- less than an hour of labor to do the job. Much cheaper recall cost, much higher consequences if the part goes bad, they still updated the part and did not feel compelled to recall. S65 Engine failure pales in comparison.

Or, more contemporarily, the S85 went through 3 major revisions over its production run to address failure modes. At no point did BMW recall earlier S85s to update parts to later versions, even though updating them "admitted guilt".

Green-Eggs wrote

I'd love to see the data to support that also.

Green-Eggs wrote

Reminder, you said you had data, and you said there was "a shockingly large proportion of them have increased clearance rod bearings" (your words). Show us the data that supports your comments whether or not you remove supercharged engines or not.

Green-Eggs wrote

I'm not sure what that means.

Green-Eggs wrote

About 10 years ago, a guy with S65 threw a rod bearing. He hit a wall. He's paralyzed and was (at the time) suing BMW.

I see where you're coming from and those are some good points, but I think this situation doesn't fit. In the case of rod bearing clearance, BMW was already fighting two class action lawsuits for bearing clearance related failures. I stand by the comment that changing the bearing design at that point would be tantamount to an instant loss in the courts and a forced recall. Furthermore in support of my comment, at least two years after the S65 left production, BMW was quietly replacing engines long out of warranty for rod bearing failures -- calling them "goodwill" replacements for vehicles which could demonstrate meticulous service records.

Reddevils7 wrote

These are more close ups. Again, done at 19,9xx miles. I'm the second owner. The code shows they're 088/089 so these are pre lci bearings with less clearance, correct me if I'm wrong. Car build date 10/09. The last few pics are of bearings I thought had more wear as it looked like there were 2 different layers present

Obioban wrote

... but, by increasing the clearance at the rod bearings, you're reducing oil pressure at the main bearings, potentially causing them to fail sooner. So, while the rod bearing life is increased by increasing clearance, engine life may not be-- and the part that is now failing is much harder to replace periodically (main bearing replacement is an engine out job).

After much deliberation, I put new OE (updated) rod bearings in my s85. Replacing them is an afternoon job-- like my S54, I will just do that on an interval I feel comfortable with. Too much potential risk associated with increasing their clearance, IMO.

Obioban wrote

I don't agree with this statement-- if you look at threads with main bearing failure, a shockingly large proportion of them have increased clearance rod bearings. IMO disproportionately many to the quantity of cars running increased clearance rod bearings.

IamFODI wrote

Thanks, guys. Think I fixed the pic.

........

The measured pressure loss definitely isn't large. But saying it's not "significant" implies that it has no meaningful effect, and we don't know that yet.

charliev68 wrote

WPC with ARP 2000. 40,000 miles.

Assimilator1 wrote

Nearly missed this amongst the discussion, they look like they're in very good condition!
Have you (or anyone) posted these bearing photos before?
Do you know what bearings they are? OEM?

charliev68 wrote

Yes, very minimal wear! Looks even better in real life, the photo shows shadows that look like wear, but is actually not.
First time, never been posted before.
Oem bearings with WPC Treatment, over 40k miles.

Assimilator1 wrote

...

I say a 4% drop in oil pressure is insignificant because the oil pressure is still above the min control oil pressure stated by BMW for the S65 (I have confirmed this on BMW's AIR site), which is 4 bar.
...

f1recracker wrote

Rod bearings serviced at 41k miles at Bimtech / Mashimarho earlier this year in Seattle WA. Car is pre-LCI 09-2009 build date.

Green-Eggs wrote

I noticed that after I mentioned the oil flow increase and minimal pressure drop, that part of the conversation died and was omitted from other responses. This might be the reason. These graphs shows what happens to oil pressure and oil flow with OEM and BE Bearings. It would be really hard to look at these graphs and argue that a "drop" in oil pressure with BE Bearings has any significance. It would be equally hard to argue that the substantial increase in oil flow is not highly beneficial.

5% throttle: http://wiki.rcollins.org/core/images/4/49/Avg_Data_vs_RPM_with_05_pct_Throttle_BEB.jpg
30% throttle: http://wiki.rcollins.org/core/images/a/a0/Avg_Data_vs_RPM_with_30_pct_Throttle_BEB.jpg
50% throttle: http://wiki.rcollins.org/core/images/d/d5/Avg_Data_vs_RPM_with_50_pct_Throttle_BEB.jpg

Assimilator1 wrote

Regarding BMW and recalls, the point about the VANOS pipe for the e46s, that is a cheap fix for a high risk of serious harm to people in the car (i.e catching fire). So perhaps not a very good example.
Replacing engines would be a very expensive recall, and whilst blown engines certainly can catch fire (but not too likely I think) and have caused accidents, I think the risk is lower than the above example (as far as a fire goes).
Countering that, BMW have and are engaged in a massive recall for checking &/or replacing EGR coolers for 100s of thousands of there diesels going back 10yrs or so (I think that's just UK figures too!), and with some cars having 3 recalls and 2 EGR cooler replacements! They have to replace so many that the factories can't keep up with supply! So as a result they are only (at the moment) calling in cars to be checked, and only replacing ones which are showing signs of leaking. This must be costing them vast amounts of money, so I don't get why BMW doesn't have a recall for the S65s (unless they're already spending too much on current and recent recalls! e.g e9x battery cables and fan plugs!).
BMW state the EGR cooler leak problem does carry a very small risk of fire, and in the 9 months I've been at BMW I'm not aware of one having caught fire brought to our dealer. We have replaced a good number that have leaked though.
So as to why BMW haven't sorted the S65s, I'm lost! lol