DIY: S65 M3 Rod Bearing

[SYT_Shadow]

For the ARPs I used the 3/8 and it felt great. Did not try the 11mm there

[admranger]

And just to make things confusing, there's also a triple square head. Points are at a 90 degree angle. It looks similar to the double hex but it's slightly different. XZN designator for the purists out there...used mostly for internal cap screw type situations. Better than torx or hex, but rare in cars.

Here's what a double hex socket looks like.



Then you have XZN and regular 12 pt for comparison. I couldn't find a similar drawing of a double hex, fwiw.

[deansbimmer]

Originally Posted by admranger

deansbimmer what do you make of those spots on the bearings? My car had those too? I'm wondering if there wasn't some cavitation going on? Thinking about the physics of that is interesting...

Cavitation is a completely different issue not usually seen in the S65 and results in a different appearance in used bearings than what is pictured above.

The wear pattern pictured is typical and from metal to metal contact. The oil film is too thin due to inadequate clearances, which results in the contact of the journal to the bearing surface in the highest stress areas. During the final few degrees of rotation during the compression stroke the upper shell sees most of the wear, so that's the area you see most worn down for each cylinder. During the power stroke the bottom shell is worn similarly.

The re-engineered bearings with increased clearances (BE) allow for a thicker hydrodynamic oil film, which will be more resistant to shearing and the resulting wear we see in these engines. There should never be any contact between a journal and the bearing surface, that's why 'most' engines usually exhibit no visual bearing wear after 100k miles.

[admranger]

Originally Posted by deansbimmer

Cavitation is a completely different issue not usually seen in the S65 and results in a different appearance in used bearings than what is pictured above.

The wear pattern pictured is typical and from metal to metal contact. The oil film is too thin due to inadequate clearances, which results in the contact of the journal to the bearing surface in the highest stress areas. During the final few degrees of rotation during the compression stroke the upper shell sees most of the wear, so that's the area you see most worn down for each cylinder. During the power stroke the bottom shell is worn similarly.

The re-engineered bearings with increased clearances (BE) allow for a thicker hydrodynamic oil film, which will be more resistant to shearing and the resulting wear we see in these engines. There should never be any contact between a journal and the bearing surface, that's why 'most' engines usually exhibit no visual bearing wear after 100k miles.

I don't get how the spots are from metal to metal contact. They are too localized.

[deansbimmer]

Originally Posted by admranger

I don't get how the spots are from metal to metal contact. They are too localized.

Which spots are you referring to then?

[pbonsalb]

What else would the wear come from?

[SYT_Shadow]

I sent pics of my 2013 to BE Bearings. I wonder what the reply will be

[admranger]

Originally Posted by deansbimmer

Which spots are you referring to then?

5th and 7th bearing in the pic below have small round spots on them (1/16" -3/32" maybe?). My bearings had spots like this too. These are small, localized round spots I'm talking about. I'm not talking about the obvious standard looking bearing wear.

Originally Posted by pbonsalb

What else would the wear come from?

Well, you tell me. It's kinda why I asked.

[deansbimmer]

Small specs like those are embedded particulate contamination from foreign materials. (usually aluminum or carbon). The babbit layer in the bearing is supposed to allow debris to embed in its soft surface to help prevent scoring of the journal. It's a built in final line of defense.

[bigjae1976]

Finally got around to sanding the bearings.

So from left to right...

1. Sanded awhile with 400 grit.
2. 2 swipes with 400 grit
3-4. Untouched

So #1, its just shiny aluminum as I keep sanding with some significant pressure. Then as you can see in #2, it takes minimal effort to remove the tan/brown marks on the bearing. I have to think that's just oil residue?

You can see #3/#4 for comparison.

After sanding, the bearing surface looks shiny vs dull on a new bearing. So I suspect that you have no way to tell what condition the bearing is in unless you measure it.

EDIT: would help if I posted pics. I took a couple hoping at least one will turn out good.

[bigjae1976]

Here are some pics of the engine mounts. They do suck. There is a top and bottom half which is connected around the circumference with rubber. In the middle, there's a space which I imagine allows for some movement and additional compliance.

I would guess that these don't last because of heat and the pass side gets pull up which causes the rubber to tear and then the top/bottom to separate.

I don't see why you couldn't use an OE mount on the driver's side and a heavy duty mount (group N or solid rubber?) on the pass side with minimal impact on NVH.

Pass side



Peeking into the driver's side

[SYT_Shadow]

Very interesting bigjae. Thank you for posting!

[sirploppy]

Very interesting. Seems the only way to determine the true condition of the aluminum bearing would be with a micrometer.

[deansbimmer]

Originally Posted by bigjae1976

Finally got around to sanding the bearings.

So from left to right...

1. Sanded awhile with 400 grit.
2. 2 swipes with 400 grit
3-4. Untouched

So #1, its just shiny aluminum as I keep sanding with some significant pressure. Then as you can see in #2, it takes minimal effort to remove the tan/brown marks on the bearing. I have to think that's just oil residue?

You can see #3/#4 for comparison.

After sanding, the bearing surface looks shiny vs dull on a new bearing. So I suspect that you have no way to tell what condition the bearing is in unless you measure it.

It's just discoloration. The bearing metals oxidize over time. Tin is especially reactive and discolors quickly. Tin is a soft metal which would be classified as the solid lubricant in the bearing alloy. The aluminum doesn't oxidize as quickly, and the silicone content dispersed from the face layer keeps the face and the crank journals polished. I don't know the exact makeup of the BMW bearings, but this is what is typical from a generic bi-metal engine bearing.

Here are some pics of the engine mounts. They do suck. There is a top and bottom half which is connected around the circumference with rubber. In the middle, there's a space which I imagine allows for some movement and additional compliance.

I would guess that these don't last because of heat and the pass side gets pull up which causes the rubber to tear and then the top/bottom to separate.

I don't see why you couldn't use an OE mount on the driver's side and a heavy duty mount (group N or solid rubber?) on the pass side with minimal impact on NVH.

The mount are actually engineered very well. It's the rubber component that doesn't last against the environment. I'm not sure what BMW recommends as intervals for the engine mounts being replaced, but they're not designed to last the life of the car. The softer the material the shorter their lifespan. There would obviously be a trade off here between comfort and durability and BMW obviously went with comfort. In some environments the bearings would have lost a good portion of their damping ability by 30k miles.

The mounts are a "hydraulic" design, as are most from BMW. The area inside where you think is void is actually filled with an oily liquid which passes in-between the perforated metal plate as the mount deflects and stretches, compressing the liquid and absorbing vibrations. This assists in the damping of vibration much better than a solid piece of rubber. Many mounts would have leaked the fluid out by the time they are replaced, so most are unaware of its lack of presence and assume the mounts are still usable.

If you've ever pulled a mount apart by accident and the fluid goes everywhere, you won't forget it. Its smelly and it stains your clothes like crazy.

[bigjae1976]

Originally Posted by deansbimmer

It's just discoloration. The bearing metals oxidize over time. Tin is especially reactive and discolors quickly. Tin is a soft metal which would be classified as the solid lubricant in the bearing alloy. The aluminum doesn't oxidize as quickly, and the silicone content dispersed from the face layer keeps the face and the crank journals polished. I don't know the exact makeup of the BMW bearings, but this is what is typical from a generic bi-metal engine bearing.

The mount are actually engineered very well. It's the rubber component that doesn't last against the environment. I'm not sure what BMW recommends as intervals for the engine mounts being replaced, but they're not designed to last the life of the car. The softer the material the shorter their lifespan. There would obviously be a trade off here between comfort and durability and BMW obviously went with comfort. In some environments the bearings would have lost a good portion of their damping ability by 30k miles.

The mounts are a "hydraulic" design, as are most from BMW. The area inside where you think is void is actually filled with an oily liquid which passes in-between the perforated metal plate as the mount deflects and stretches, compressing the liquid and absorbing vibrations. This assists in the damping of vibration much better than a solid piece of rubber. Many mounts would have leaked the fluid out by the time they are replaced, so most are unaware of its lack of presence and assume the mounts are still usable.

If you've ever pulled a mount apart by accident and the fluid goes everywhere, you won't forget it. Its smelly and it stains your clothes like crazy.

The part about the bearing discoloration...makes sense to me. It comes right off so the discoloration seems like a poor wear indicator.

As far as the engine mounts. I can agree that they are trick engineered parts.

But they are shiet for this application which is supposed to be performance oriented. Should be solid rubber but I guess the waxers and empty nest former soccer moms don't like engine noises.

[SYT_Shadow]

Originally Posted by bigjae1976

The part about the bearing discoloration...makes sense to me. It comes right off so the discoloration seems like a poor wear indicator.

As far as the engine mounts. I can agree that they are trick engineered parts.

But they are shiet for this application which is supposed to be performance oriented. Should be solid rubber but I guess the waxers and empty nest former soccer moms don't like engine noises.

I have the BW mounts on the E90 which is more track focused. I suspect with a raised idle to 1000rpm they will be indistinguishable to stock. As is, they're slightly harder and where you can really tell is at idle, especially when the DCT makes the engine dip lower than the regular idle.

On the E92 I went with OEM mounts. Mine seemed to be ok after 30k miles so they'll hopefully take another 30k

[///M3 Gusta]

I started working on this over the weekend- this evening I replaced the bearings and am at the point where I can start putting things back together. The car is a 2008 with 55,xxx miles. PO was not aware of the rod bearings being changed, but these are definitely look like the newer type of tin/Al matrix to me. I changed them out anyway, replaced with BE/Clevite rod bearings and Carillo rod bolts courtesy of Lang Racing.



The row on the left were in the upper position, and all look like they have more wear than the lowers. Cyl. 1 is at the bottom working up to 8.



180 degree view trying to capture the shells that were in the cap end.

And since we're talking about motor mounts, mine are pretty well trashed:

[SYT_Shadow]

Amazing, those definitely look like the new type! How unexpected.

And yeah, those engine mounts were torn to pieces!

[deansbimmer]

I dunno, it may be the small dark photos but to me they appear to be the old cu/pb bearings not the tin/alum. Good job on doing it yourself.

[///M3 Gusta]

Originally Posted by deansbimmer

I dunno, it may be the small dark photos but to me they appear to be the old cu/pb bearings not the tin/alum. Good job on doing it yourself.

Now that I've had time to look at them and think about it you're probably right.

[admranger]

Lewis Black looks pissed at the condition of the bearings.

[olaf m3]

So helpful thank you 🤗