Yes, another rod bearing thread

[BMRLVR]

The reality is that some S65's have rod bearing issues that some of us believe are clearance related. With that being said the majority of the posters on here have been driving their cars with no issues. No one can tell you if your engine has these issues without disassembling the engine, inspecting the bearings and crank journals and measuring the clearance.

Obviously you can tell from my participation in rod bearing threads that I believe in the issue, but I also believe that some engines have a favourable tolerance stack up on their side and they end up being fine. Basically if you intend to keep the car for a long time you have to decide if you want to be one of the people who does his bearings as preventative maintenance or just drive and hope everything keeps running fine. There is a good chance you will be fine, but I feel that with these engines there is always a small chance of having issues.

[Rat3d ///M]

Originally Posted by regular guy

Anybody else notice that it's comments like this that always appear in any thread with anybody asking a legitimate question. These posts always seem to precede all others on the topic. These are the true hysteria posts in my opinion.

Not quite sure where you are going with this, but whatever.

[Killerfish2012]

Originally Posted by SenorFunkyPants

On the balance of probabilities there is every reason to believe that your car can complete a high mileage without any engine problems.
Despite suggestions to the otherwise, running to the redline is not beneficial to long engine life. The highest loads on the bearings and reciprocating parts occur at max rpm...combine that with elevated oil temps to further increase risk.
Not that owners shouldn't run to the red line - its what the car was designed for, but I don't find much performance benefit in using the last 500 rpm.

You've still not been able to explain why our track section, full of hardcore enthusiasts with the videos to prove it seem not to suffer from bearing failures? It's the guy with 4 posts, who's "blown his motor", and wants a thread with a thousand views in one hour, that we keep hearing from.

As long as there were no assembly issues, maintenance plays a much bigger role than driving style.

[Killerfish2012]

Originally Posted by bradleyland

Meanwhile, Yost racing completed 25 Hours of Thunderhill on stock internals.

OP, obviously we can't just wave our hands and get you to stop worrying about the issue, but you've got to approach it rationally. A few of things to keep in mind:

1) This is an internet forum. The population here represents a very small portion of the overall M3 ownership population.

2) As is the case with all outlets for frustration, the vocal minority is strong here. Again, I'm not saying you should ignore the issue, but I am saying you should approach it rationally, which requires that you evaluate the opinions you're hearing in context.

3) Based on the numbers we have, it is exceedingly unlikely that you'll experience bearing failure. I tabulated all the production numbers for the M3 (worldwide) the other day, and BMW sold around 60k M3s across the globe. Of the people who have experienced rod bearing failure, many were modded. You can hardly be surprised when someone running a supercharger pushing 50% higher than the designed horsepower rating of the engine grenades a motor. If there were 200 failures of stock engines, that would represent about 1/3rd of 1%. The numbers we have suggest that the failure rate is not that high.

4) Even if you are one of the people who experience failure, there's a reasonable chance that BMW will fix the car for you, provided you haven't modified it significantly. Since we're all reasoning from anecdotes here, there are examples of individuals who experienced rod bearing failure outside of the factory warranty, and BMW still replaced their entire engine. It is not in BMW's interests to have a reputation for exploding engines; especially the S65. Of course, if you drive in with obvious signs of modification, they're going to put you out on your ear.

5) No one has the real failure rates but BMW, and it's unlikely that we'll ever get that information.

There is no fail-proof method of preventing the issue, but there are things you can do to mitigate it. When you have your oil changed, you can send it off for a lab report. If there are elevated levels of zinc and lead, you can spend $2,400 on rod bearing replacement and save the motor.

There are members here who will chime in and point out that the oil test procedure isn't 100% effective. They're right. There is no 100% effective solution, but if you're shooting for 100% assuredness, you should sell your car immediately and move in to an underground bunker, because you have a better chance of being struck by lightning than you do buying a car that has a 100% chance of trouble-free operation.

Be rational about it. Do what you can to mitigate your risk, and enjoy your car.

"Human beings are Irrational"- Sigmund Freud 1800s

[Killerfish2012]

Originally Posted by BMRLVR

The reality is that some S65's have rod bearing issues that some of us believe are clearance related. With that being said the majority of the posters on here have been driving their cars with no issues. No one can tell you if your engine has these issues without disassembling the engine, inspecting the bearings and crank journals and measuring the clearance.

Words of wisdom. Everyone seems to want to push the idea that when you change the rod bearings and bolts, your risk of future failure magically goes away, ignoring some key facts that never seems to get mentioned:

-Your new assembly torque specs have to be right
-Your rods are old, and most likely a little stretched out from the heat of use.
-Your main bearings have about the same amount of wear as your rod bearings, and you didn't replace them.