Main bearings: Genuine concern or paranoia

[M3MorganAUS]

Morning/Evening,

I would like to get some veteran owners opinions. I have a higher mileage E90 M3 LCI. I’ve been reading about main bearing failure on these later model cars (and some Pre-LCI cars) and to be honest it scares me.

My rod bearings are going in to be replaced in June with ACL HX extra clearance bearings and BMW bolts as I have no paperwork for them ever being done. But reading about the mains makes the whole thing seem pointless. I love the car, but in Australia engines are rarer and getting more expensive. It’s ruining the whole experience for me and makes me think I’ve bought the wrong car (I originally wanted an E46 SMG or an F82 DCT) but fell in love with the E9X shape and sound and technology.

Am I crazy and/or stupid? Or are my fears and anxiety justified?

[kolosy]

doing the mains is more expensive than buying a new engine. doing the rod bearings is a few K (at least here in the US). i think it's worthwhile insurance to do the rods since they do show up worn in the rod bearings thread.

[PiZauL]

As someone that bought a high mileage E90 M3 recently, I'm with you. Belonging to a forum you will see all the issues with any platform; its where folks come to seek help when there IS an issue. It's part of being an enthusiast, being overly aware of potential issues. What you don't see is all the non-issues from non-enthusiasts that enjoy the car. My car for example, previous owner was an older gentleman that took care of the car and followed the dealership maintenance to the tee, he had NO idea these even had a rod bearing concerns. I just did the rod bearings, and they were nearly perfect.

Takeaway I have taken after many sports cars and belonging to forums, is enjoy the car. Any car can fail at any moment for any given reason. It's no reason to drive in fear. The rod bearings have a very low percentage of failure as a whole, and main bearings are even rarer than that. As with owning any performance car, have a maintenance budget (yes budgeting for a whole engine replacement is easier said than done especially in Australia). Or get a cheap beater and enjoy the car on nice days to lower the wear and tear.

[omgzirra_exe]

I do tend to agree that main failures seem to result more from a lack of oil than anything else, especially in "high performance" environments.

Having debris in your oil pickup tube can also cause your mains to fail, because, guess what, that's where you pick up oil. although the chances of that happening are also very rare, but can be plausible due to the plastic vanos covers cracking and the material build up would clog the pick up tube.

As long as you upkeep everything else, you should be fine. In my opinion, the biggest issue is that most S65 owners are not accustomed to the amount of oil needed for high-revving engines. Coming from high-revving Hondas, it makes a lot of sense to me to add a bit of oil before a track day or a "spirited" driving event even though I'm showing "full". - in the end it always comes down to oil.

[charliev68]

Mains will go longer in comparison to Rods. IMO, the s65 engine needs to get the Mains refreshed eventually, just like any other “race” style engine. I think you will be safe up to about 150k miles. It’s a gamble because once you spin a Main, your engine will become “parts”

[M3MorganAUS]

Originally Posted by charliev68

Mains will go longer in comparison to Rods. IMO, the s65 engine needs to get the Mains refreshed eventually, just like any other “race” style engine. I think you will be safe up to about 150k miles. It’s a gamble because once you spin a Main, your engine will become “parts”

The problem is the mains border on a full rebuild. A shop in another state quotes about 5500 to do mains and rods, but as deansbimmer says it’s not great to do them in the car. It’s hard because unlike the rods, it’s not an “easy” check and replace and you’ll never know it’s going until it’s gone and you have a 4litre paper weight. Just ruins the whole experience.

[charliev68]

I feel you. If I couldn’t do the work myself, I would be weary about owning our beloved s65 m3. I think that’s why it’s also so special. Cost of “Cool”!
Even buying another engine, the root catastrophic problem still potentially exists. If people keep driving their engines until it spins a Main, s65s will eventually disappear and younger generations will never get to experience the last NA v8 BMW will ever produce. That would be truly sad 😔

[e90sanmarino]

Replacing the mains as some have stated is a costly endeavor. Especially depending where you located at the labor price can vary. One other option is going stroker kit from Carbahn if you are planning on keeping the car for a very long time. Thats what I personally did

[M3MorganAUS]

Originally Posted by e90sanmarino

Replacing the mains as some have stated is a costly endeavor. Especially depending where you located at the labor price can vary. One other option is going stroker kit from Carbahn if you are planning on keeping the car for a very long time. Thats what I personally did

I’ve thought about it, but I can’t do it. I bought the car to keep as OEM as possible, and no one in my area has experience with the S65 in that aspect. Plus, the shipping and fees would absolutely kill me.

[e90sanmarino]

Originally Posted by M3MorganAUS

I’ve thought about it, but I can’t do it. I bought the car to keep as OEM as possible, and no one in my area has experience with the S65 in that aspect. Plus, the shipping and fees would absolutely kill me.

Thats actually the reason why I did it. I’m located in Vietnam which has less than 9 E9X M3 in the country. There’s no garage with expertise and resources locally to do the rebuild. Which is why I’d rather have someone with a lot of experience do it and eat up the cost but having a piece of mind with a warranty. I believe CarBahn quoted me 2000$ for shipping to Vietnam. If you return the engine core to them in good condition they deduct 10,000$. So the stroker 4.6L stroker should be around 31,000$. Not including all the preventative parts you are going to do while you have the engine out of course. I believe their 4.2L stroker is much cheaper but I don’t have the specifics.

[deansbimmer]

Main failures do happen but it's not worth the risk or cost to open the engine for replacement unless you're rebuilding the entire engine. If you're just wanting to update the mains and nothing else I would advise against it. There is a high risk of introducing more issues than you're fixing. Their rate of failure is much lower than rod bearings.

[charliev68]

Originally Posted by e90sanmarino

Thats actually the reason why I did it. I’m located in Vietnam which has less than 9 E9X M3 in the country. There’s no garage with expertise and resources locally to do the rebuild. Which is why I’d rather have someone with a lot of experience do it and eat up the cost but having a piece of mind with a warranty. I believe CarBahn quoted me 2000$ for shipping to Vietnam. If you return the engine core to them in good condition they deduct 10,000$. So the stroker 4.6L stroker should be around 31,000$. Not including all the preventative parts you are going to do while you have the engine out of course. I believe their 4.2L stroker is much cheaper but I don’t have the specifics.

Wholly Shite!!! 31k+?! Gosh Dang…that’s a lot of money!!!
But, if the man that wrote the diy on MB replacement says not to do it…not much options available.

[M3MorganAUS]

Originally Posted by deansbimmer

Main failures do happen but it's not worth the risk or cost to open the engine for replacement unless you're rebuilding the entire engine. If you're just wanting to update the mains and nothing else I would advise against it. There is a high risk of introducing more issues than you're fixing. Their rate of failure is much lower than rod bearings.

Just the man I was hoping to hear from. What are the potential issues with replacing the mains? Even if I were to take the engine out of the car and do it, would I still face the same issues? There is a well known shop in another state that does them in car with rods included for 5500AUD. I plan on keeping the car long term . As it stands I have put 10000 relatively trouble free kilometres on it with the car now sitting at 191000km. Still on original rod bearings and I’ve had the VANOS and rocker covers (yes the entire cover) replaced and it has been serviced every 5000km in my ownership and 10000km in the previous owners tenure. I love the car, whenever I drive it I get a lot of joy. I have a daily now, but the thought is always in the back of my head “what if my bearings go and I have to bin the block”. I am not in a logistical and financial position (yet) to replace the power plant in the car, the S65 is hard to find used here in Australia and new blocks are hard to come by.

[deansbimmer]

Regarding any shop offering a main/rod bearing replacement at those prices, the parts alone cost such that there is no way they're doing quality work for what's left over to cover labor.

The problem is multi faceted. Yes, the job requires precision and very high attention to detail and cleanliness. Not many shops function at that level. Those that do would never permit mains to be replaced in-car, nor would the job ever be realistic at that low a price.

Overall, the risk of failure is low, and I'm ok advising my customers to assume that risk as opposed to bearing the expense of an engine-out repair. Furthermore, in all the 08-13 M3's I've owned personally, none had their mains replaced. Just do the rods and don't worry about mains.

[M3MorganAUS]

Originally Posted by deansbimmer

Regarding any shop offering a main/rod bearing replacement at those prices, the parts alone cost such that there is no way they're doing quality work for what's left over to cover labor.

The problem is multi faceted. Yes, the job requires precision and very high attention to detail and cleanliness. Not many shops function at that level. Those that do would never permit mains to be replaced in-car, nor would the job ever be realistic at that low a price.

Overall, the risk of failure is low, and I'm ok advising my customers to assume that risk as opposed to bearing the expense of an engine-out repair. Furthermore, in all the 08-13 M3's I've owned personally, none had their mains replaced. Just do the rods and don't worry about mains.

Thanks Dean, I will get the rods done. I am using ACL HX extra clearance bearings. Ive read that this could drop the oil pressure to the mains. Will this be an issue?

[spammysammich]

You’ll never get clear consensus on the effect of the drop on the mains reading the debate here. Both camps give compelling arguments. In theory the oil pump should be able to increase flow enough to minimize loss due to clearance or tolerance stacking.

[Oreo Cat]

im at 153k miles on OG RBs and MBs. 60k SC'd. I will probably never change the mains and won't change rods until the oil pan gasket it replaced. I bought my car from a responsible older man and I dont drive it hard very often and never push it when the oil is cold. Car has been on road trips in CA, NV, OR, WA, ID, MT, WY, UT, CO, NM, AZ in all weather and still runs great

[deansbimmer]

Originally Posted by M3MorganAUS

Thanks Dean, I will get the rods done. I am using ACL HX extra clearance bearings. Ive read that this could drop the oil pressure to the mains. Will this be an issue?

Oil flows through the mains then to the rods. The pump features variable displacement. The pump will adjust flow to maintain the required pressures. However, we don't recommend the HX set as most sets measure a little too much clearance. I sell a set of mixed and measured 1580H/HX that are WPC treated. If you want ACL those are the way to go. Or use BE.

[GORDON.M3]

If you are opening up the Engine for the sake of just doing Main Bearings and nothing has gone wrong with the motor yet I would advise not to.

Any shop that can tell you they can do your mains but don't open S65s regularly I would steer far away from. It's not a job for the regular joe BMW mechanic. Changing mains needs an extreme level of detail and precision and daily experience with opening up S65s.

I've heard about horror stories of V10 S85s being rebuilt by a known engine builder and blowing up because the bed plate was sealed with black RTV Silicone (LOL).

[charliev68]

Sarka on the Ring and m539 have very comprehensive YT videos on what the job entails. Sreten covers it very well in his entertaining videos!

[M3MorganAUS]

Originally Posted by deansbimmer

Oil flows through the mains then to the rods. The pump features variable displacement. The pump will adjust flow to maintain the required pressures. However, we don't recommend the HX set as most sets measure a little too much clearance. I sell a set of mixed and measured 1580H/HX that are WPC treated. If you want ACL those are the way to go. Or use BE.

What’s the issue with opening them up a bit more? Is it the higher oil pressure required?

[BGBF18]

FWIW, I had my RBs done a few months ago. ~70k miles, three owner car, 2011. Bearings had virtually no wear. The shop I used has done many of these replacements and felt these could have gona another 70k. Oh well, at least they’re done.