E90 conn rod bearings. 1

[rQuestionEngineering]

It's foolish to buy E90 just to discover the need to replace con rod bearings is a form of maintenance.

It does not happen to low cost cars.

From design point of view, what can be improved?

https://m.youtube.com/watch?v=gijJhMWg3RQ

 

[TugboatEng]

Rod bearings are a maintenance item on the Cat 3500 series diesel engines. Cylinder heads get replaced at mid-life as well.

For the E90 bearings, it looks like they use a surface treatment, WPC, to improve load carrying capacity. Journal bearings wear during engine starting and stopping. It's possible that the bearings don't have sufficient load carrying capacity once the coating is gone. From what I see the treatment is only 5-20um thick.

 

[BrianPetersen]

That's the 4.0 litre S65 V8 non-turbo engine. I know nothing specific about those, other than that BMW does not do V8 engines well. They do inline sixes better.

From the end-user point of view (1) buy something else, or if you are stuck with one (2) follow oil change recommendations religiously, both concerning the intervals and the viscosity and specifications, and (3) avoid the driving conditions in which rod bearings are most heavily loaded ... low revs and high torque (lugging), and high engine load near or above redline, and operation with high oil temperature.

Minor investigation finds that this issue is common enough that the aftermarket has what they claim is an improvement:

https://www.ecstuning.com/b-be-bear...-connecting-rod-bearing-set/sp1527hkstds65~b/

They claim that the OEM setup has too little oil clearance. I have no specific knowledge about that specific application ... but too-tight rod bearings can certainly lead to trouble.

Different vendor similar description of problem

https://mashimarho.com/products/be-rod-bearings-m3-s65-e90-e92-e93

BMW recommends 10w60 oil for these. Wouldn't surprise me if an oil change at the generic auto parts shop around the corner leads to the wrong oil being put in, followed by badness.

 

[gruntguru]

Wow. 60 wt oil in tight-clearance bearings!

je suis charlie

 

[cibachrome]

Why not just have the dealership change the bearings when you have them change the oil ? Probably not more that a 10 minute job. Make sure they replace the oil pan gasket and not reuse the old one.

E90 isn't really a World Class BMW anyways. It's the "Ladies & Prep School" idol platform. Why not get an E46 REAL BMW: The last of the best. Make sure it has the Conti tires though ... E-Drive ? That's for IT workers.