S65 Engine Main Bearing Service, Documented

This is great info.

Just had the crankshaft removed from my old broken engine. Thanks alot for that tutorial. Master respects for you, deansbimmer

Just would like to observe that on step 4, the sequence seems to be in opposite way.

"there is a sequence (inside outwards) that must be followed"

should be from outside inwards by the TIS. I was confused when I got there, had to check the TIS then proceed outside inwards.

Out of curiosity, why do you not recommend replacing the mains preventively @deansbimmer?

I ask bc I just finished rebuilding an s54 (down to mains) for a swap car. It’s up and running and I’m elated, but I’m also slightly bored.

So I was thinking about a 1 series s65 swap. But I’m going to go through that trouble I was thinking to rebuild the s65 first. New mains, rings, rod bearings, etc.

Is it bc it’s just risky to go all the way in there as is anything extraneous?

GREATLY appreciate this thread. Amazing and thanks for all the tips.

He mentions this in the op The mains also wear poorly but fail at a lower rate than the rods, therefore I believe most owners are willing to accept the risk.

He also mentions it's about 30hrs labour!
So I would guess he doesn't recommend it because of a very(?) low risk of failure and a very high cost.
But it'll be interesting to hear what he says about it.

tlow98 wrote

Out of curiosity, why do you not recommend replacing the mains preventively @deansbimmer?

For the reasons mentioned.
-Statistically lower number of reported failures than rod bearings.
-Mechanically lower risk of failure, they wear differently and slower.
-Split bed plate design = exceptionally high labor requirements and more involved than individual cap design like S54 which are quite easy.

It's not a "while you're in there" job. Mains require engine removal and teardown. Even at the minimum feasible job scope your total investment should still rival the cost of a replacement engine. It doesn't make financial sense.

If you found someone willing to do it cheap, it wouldn't be up to the correct standards of precision or cleanliness to provide a lasting solution. Done properly, it will always be expensive. You'd be better off leaving the factory mains in place. When it comes time to do mains, you should be at high miles and doing a complete rebuild of the engine.

deansbimmer wrote

.....

When it comes time to do mains, you should be at high miles and doing a complete rebuild of the engine.

Care to define 'high miles'?

Assimilator1 wrote

Care to define 'high miles'?

M539 restoration has an M3 with about 140,000 I think and the main bearings failed

M3_Legend wrote

M539 restoration has an M3 with about 140,000 I think and the main bearings failed

could it be the rods first?

Failed mains would damage the rod bearings too, because that's the direction of oil flow.
I can't see how it would happen the other way around, as the oil filter would catch any debris before it went back round.

M3_Legend wrote

M539 restoration has an M3 with about 140,000 I think and the main bearings failed

Wasn't supercharged was it?
Got any more info on that car?
[edit] Nm, just realised I've seen his youtube video about it, it's the one the crankshaft snapped in 1/2!!

RIP another S65 anyway

Crazy here is an M3 with 225,000 miles original owner

M539 Restorations tore down his donor S65 and said that the main bearings looked worn.

Is that something we need to start being concerned about now?

His theory on the double row chain tension is interesting. But for now an N=1 isn’t going to make me rush out and drop my engine. I’m still more worried about the rod bearings. After 15 years you would think that if the mains were as serious an issue the word would be out and the service as common as rod bearings. It is no doubt a point of concern though.

Redd wrote

M539 Restorations tore down his donor S65 and said that the main bearings looked worn.

Is that something we need to start being concerned about now?

Scroll up a few posts from June 24th and you'll see that's recently been answered , including by Deansbimmer.

deansbimmer Mporium has to be one of the best Bimmer shops in the nation conducting successful open heart surgery on the S65. Sub'd. I just found this thread. And a good thread maker too. Wow.
.
https://mporiumbmw.com/

Assimilator1 wrote

Scroll up a few posts from June 24th and you'll see that's recently been answered , including by Deansbimmer.

Ah thanks. Must have overlooked it.

I wouldnt consider doing the mains without rebuilding the engine, the scope of the job requiring engine out/full disassembly would be foolish not to rebuild the engine "while youre in there".

Every Youtuber wants to inject their own theory and attempt to create some new buzz on a topic, but it's still the same well established basis.

Even now, as these old cars begin to show their age and we see more consistent wear and failure of certain components, the main bearings remain low on my concern list. Do the rods and don't worry about the mains.

It's too costly to do the mains and introduces too much potential for creating new problems unless you're doing a complete and proper engine rebuild.

Just wondering. If BMW had a thing to make tolerances a tad too tight (just like RBs), wouldn’t it be wise to put in the loosest main bearings in all journals?
Wouldn’t that be playing it safe for the long run?

deansbimmer wrote

Every Youtuber wants to inject their own theory and attempt to create some new buzz on a topic, but it's still the same well established basis.

Even now, as these old cars begin to show their age and we see more consistent wear and failure of certain components, the main bearings remain low on my concern list. Do the rods and don't worry about the mains.

It's too costly to do the mains and introduces too much potential for creating new problems unless you're doing a complete and proper engine rebuild.

deansbimmer
Looking to do full engine rebuild. Looking for service or purchase a complete engine. Do you provide such service?

In M539's video he mentions that King main bearings will be used for the rebuild. Given these have been available for a few years now, do any of the rebuilders have experience and feedback on them? deansbimmer Malek@MRF ?

E92_BGDoc wrote

In M539's video he mentions that King main bearings will be used for the rebuild. Given these have been available for a few years now, do any of the rebuilders have experience and feedback on them? deansbimmer Malek@MRF ?

I went on King’s website. It seems they only make Std and Oversized Mains.
Unless you’re engine is lucky and is GGGGG, it might be too tight

We've used King main bearings plenty of times without issues. They just need to be installed and measured before assembly, which should be done with any engine build using any kind of bearings. BMW's color ID only works if you're simply replacing bearings in an otherwise unchanged bottom end, i.e. reusing the same crank in the same block.