DIY: E46 M3 S54 detailed rod bearing replacement and front suspension refreshment

[Slideways]

Oh brother I know, I feel it every time I work on the car, and all the items I've added onto the maintenance list due to the "while I'm in there" aspect. While I think it'll be worth it in the end, the scope creep has me exhausted with how many diagrams and parts I am keeping track of and trying to remain organized.

I think today I'll finally be able to check the status of the bearings, which were claimed to have been replaced at 75k miles (18k miles ago), but I suspect I'll find them to be original since the engine mounts looked to be from the factory and pretty worn, along with not being able to find the proper service records for them.

Depending on how those bearings look, they should be perfectly reusable if they do indeed have 18k miles on them.

[beemer_guy]

Depending on how those bearings look, they should be perfectly reusable if they do indeed have 18k miles on them.

That would be great if they were, as I think the set I ordered (slightly oversized) may have been the wrong move, I didn't fully understand the clearances when I ordered them.

The only reason I am suspicious that they weren't replaced is because of the engine mounts, it seemed strange to me that they would've gone through the effort to replace the bearings but not refresh something as simple as those while the subframe would've been dropped anyways, but alas we'll see.

Edit: I am now positive the rod bearings were worked on, although how well the job was done is another question. I am absolutely certain the same dumb shop that did the water pump and thermostat replacement previously is the one that did this job due to the excessive overuse of RTV, and I am struggling to remove the pan even with all the bolts removed...

Edit 2: I managed to get the pan off after some prying harder than I was comfortable with, since scraping the exterior where all the RTV squeezed out and light malleting didn't work, and the bearings were replaced and ARP bolts were used. I still have to remove them to check but I imagine the bearings will be fine, although I don't have a micrometer to test the bolts to see if they were torqued/stretched correctly.

[beemer_guy]

So I've ended up removing some of the rod bearings, they were newer but I have questions about what I'm seeing. Unfortunately I scratched the coating on a couple trying to remove them so I'm going to have to replace them anyways, but some things I noticed:

1. The inner surface that is in contact with the crankshaft seemed fine, but the outer surface with the con-rods looked strange/worn, although thankfully the crankshaft looked pretty clean
2. The bolts were ARP bolts, but I don't believe they were torqued down to the correct value/stretch, and while I've only removed the bearings for cylinders 1 & 6, I used the stretch gauge to see how far they installed and all 4 bolts were at half or less of the stretch value of .0065-.0070 in.

I'll add some pictures in a bit and continue removing the other bearings but if anyone could expand on what I've seen I'd appreciate it because I don't want to be overthinking things.

[0-60motorsports]

So I've ended up removing some of the rod bearings, they were newer but I have questions about what I'm seeing. Unfortunately I scratched the coating on a couple trying to remove them so I'm going to have to replace them anyways, but some things I noticed:

1. The inner surface that is in contact with the crankshaft seemed fine, but the outer surface with the con-rods looked strange/worn, although thankfully the crankshaft looked pretty clean
2. The bolts were ARP bolts, but I don't believe they were torqued down to the correct value/stretch, and while I've only removed the bearings for cylinders 1 & 6, I used the stretch gauge to see how far they installed and all 4 bolts were at half or less of the stretch value of .0065-.0070 in.

I'll add some pictures in a bit and continue removing the other bearings but if anyone could expand on what I've seen I'd appreciate it because I don't want to be overthinking things.

Those bearings look great to me. I would put them back in if you cant feel any of the scratches you mention on the inside cant be felt with your finger nail. Use assembly lube as well.

[beemer_guy]

Those bearings look great to me. I would put them back in if you can feel any of the scratches you mention on the inside cant be felt with your finger nail. Use assembly lube as well.

I would love to put them back in but being the dummy I am those scratches are deeper enough to feel, I was trying to gently pry some of them with a pick since they were stuck (or I'm just not doing it correctly) and my hand slipped a couple times, I didn't realize how soft the coatings were. Only 2 of the marks barely catch my fingernail, but since I've already gotten to this point I don't want to risk it and will just replace everything.

I believe these are BE bearings, the ones I have are the ACL 6B1569HX-STD's with .025mm additional clearance, although I have to check with the plastigauge to even see if they are correct.

[0-60motorsports]

I would love to put them back in but being the dummy I am those scratches are deeper enough to feel, I was trying to gently pry some of them with a pick since they were stuck (or I'm just not doing it correctly) and my hand slipped a couple times, I didn't realize how soft the coatings were. Only 2 of the marks barely catch my fingernail, but since I've already gotten to this point I don't want to risk it and will just replace everything.

I believe these are BE bearings, the ones I have are the ACL 6B1569HX-STD's with .025mm additional clearance, although I have to check with the plastigauge to even see if they are correct.

Ok good then yes replace them. ACL should be fine but go ahead and plasti gauge them any way. If i didnt have plastigaige on hand id slap them in any way LOL

[beemer_guy]

Ok good then yes replace them. ACL should be fine but go ahead and plasti gauge them any way. If i didnt have plastigaige on hand id slap them in any way LOL

I actually bought 2 packs of plastigauge since I was paranoid I'd mess it up haha. I'm about to test it now, let's hope I get lucky!

[0-60motorsports]

I actually bought 2 packs of plastigauge since I was paranoid I'd mess it up haha. I'm about to test it now, let's hope I get lucky!

YES! Waiting for results. I was thinking of buying the ACL STD for my own car and another friends car.

[beemer_guy]

YES! Waiting for results. I was thinking of buying the ACL STD for my own car and another friends car.

So, bad news, and more questions.

The stretch gauge:

I don't know if I was using the stretch gauge correctly, I zeroed it with a bolt that was not installed into anything, but when I installed the cap onto the con rod, and even barely had the bolts threaded it would show a different stretch value, and the same at finger tight. I re-zeroed it at finger tight and tightened in increments of 30 Nm 50 Nm and 68 Nm (50ft lbs. per ARP) and the gauge just would not show the bolts stretching much, I'm not sure if I should've been more liberal with the application of ARP's lube (applied to the threads and underside of the bolt head as instructed), but at 68 Nm for both cylinders 1 & 6 showed pretty much the edge of clearance, from .065-.075 mm which I wasn't comfortable with.

I can try again later and use the "old" ARP bolts to see if they make a difference, but for the time being it's looking like I need to get the non-oversized bearings, ACL 6B1569H-STD, which are $40 more and I probably can't return the HX's.

The plastigauge worked as it should've, don't think there was any issue with it.

The BIG question I have, is while removing the rest of the bearings (which were all in good condition, and making more regret my choices), I found that while trying to remove the top bearing for cylinder 3, I could twist the connecting rod and therefore the piston in the cylinder (horizontally), which freaked me out since that didn't happen with any of the other cylinders/con-rods. Does anyone have any experience regarding this, are the clearances just loose enough for it to spin?

I'm prertty worried, and I've already borescoped the cylinders before and found some (slight-medium?) scoring, and pulling the engine and investing any more money into this is a no-go and out of my means for a while at the very least. I've attached some pictures of the scoring for reference, I honestly couldn't find a reference to tell if they were terrible or just ok. I did remove the fuel injectors and get them cleaned, apparently they had been leaking which would explain the scoring.

Edit: Adding to this post because I'm an idiot. I referenced it as .0065 - .0070 in. in an earlier post, that is correct, I don't know why I reverted to mm and more importantly, .065-.070 instead. It really threw me off with understanding how far the stretch gauge needed to move, I needed to look at the individual tick marks, instead of thinking I needed the dial to go to 1 full REVOLUTION, which I wouldn't have tried pushing the bolts that far, but if I did they absolutely would've snapped before even making it close to that value. Ugh, I'm glad I caught this as this makes things much simpler.

[maupineda]

The scoring is very light and will run ok with maybe some oil consumption.

do not use oversized bearings, BMw designed the engine with that in mind and so everything else is calculated based on that. I would used original bearings and accept you need to replace them every 100k miles which is not that bad actually. I mean, for most people that is a once in a lifetime service.

same For bolts, just go OE and follow the recommended procedure. The idea of ARP reusable bolts is great but seems to me the stretch method is just as cumbersome as the OE one

[Slideways]

Would have reused those bearings with new bolts.

If every S54 owner bore scoped their cylinders, they would find some wear, minor scoring marks included. Don't go looking for something to replace. It is a used engine and they can go many miles looking like that. Now, if you have compression loss or excess oil consumption, then you should be worried.

[beemer_guy]

The scoring is very light and will run ok with maybe some oil consumption.

do not use oversized bearings, BMw designed the engine with that in mind and so everything else is calculated based on that. I would used original bearings and accept you need to replace them every 100k miles which is not that bad actually. I mean, for most people that is a once in a lifetime service.

same For bolts, just go OE and follow the recommended procedure. The idea of ARP reusable bolts is great but seems to me the stretch method is just as cumbersome as the OE one

Yes, I'll be ordering the regular size bearings, which should get me right in the middle of the spec, but for the bolts I'll be using the ARP still since I already bought my set and can't return it either. I do agree the the BMW method is simpler, and for what I paid for the stretch gauge easily could've gone towards the BMW angle gauge or other maintenance items.

[beemer_guy]

Would have reused those bearings with new bolts.

If every S54 owner bore scoped their cylinders, they would find some wear, minor scoring marks included. Don't go looking for something to replace. It is a used engine and they can go many miles looking like that. Now, if you have compression loss or excess oil consumption, then you should be worried.

That's good to know, and trust me, I definitely am not trying to replace anything else, especially with everything else I've done so far, I very much would like to have the car put back together and running. Unfortunately since I scratched some of the bearings and can feel them with my nail I don't trust them enough to put back in, and didn't want to risk having to do this all over again. It's too bad that it was only after removing the first 2 bearings that I figured out how to properly remove the others.

Do you have any idea regarding cylinder 3's piston being able to twist fully in the cylinder? That's the part that's worrying me the most at this point, I tried to find any info about that but nothing turned up, probably due to my wording. I imagine it's normal for there to be some clearance when cold and have the rings expand and hold it in place when running, but I don't know why it was the only one I could do that to.

Edit: Can disregard the last paragraph, I was able to spin the other pistons in the other cylinders too, I realized that I couldn't before due to clearance/location of the counterweights. Dumb thing to be worried about, but in my defense it was 4 A.M and I was exhausted.

[beemer_guy]

The standard ACL bearings seem to be the correct choice so far, as I've tested them on cylinders 1 & 6 and am sitting around .045 - .050 mm clearance. I have not had the chance to test the other cylinders yet, because for the life of me I cannot manage to get the ARP stretch gauge to work correctly, and I am wondering if it is even possible to properly utilize it while underneath the car. This is the 3rd time I have torqued the same new ARP bolts, with ARP lube applied as directed, and threads being cleaned, etc., and yet as I torque in stages up to 68 NM (50 ft-lbs. as directed by ARP's sheet), the stretch gauge only shows an increase of .0008" on one bolt, and a negative reading of .0002" on the other. I know that the one bolt with the negative reading is the only outlier in length out of all the other bolts, but this same general pattern of minimal stretch has held true for every time I've torqued the bolts on cylinders 1 & 6, and it is driving me insane.

My sequence has been as follows:

1. Zero gauge to uninstalled bolt as a control and put 1 black marker on it
2. Install rod cap and install bolts with ARP lube to finger tight, attach stretch gauge and zero.
3. Begin torque sequence of 15 Nm, 30 Nm, 45 Nm, 55 Nm, 68 Nm
4. Cry because the stretch gauge shows no/negative stretch, which seems literally impossible

Things to note:

• When zeroed, both bolts show as the same value of zero
• After first torque sequence to 15 Nm, the gauge reflects the .0005" -.0007" stretch value for the 1st bolt, and -.0002" - -.0005" value for the 2nd, and does not change after this point.
• The gauge when zeroed on the control sits in the middle of the gauge's range, at .05", and on the finger tight bolts, .0005" less, for some reason.
• The gauge is not contacting anything else, is sitting on both ends of the bolts correctly (verified every time with a mirror or borescope), and is upside down since that's the only way to attach it to the bolts
• The gauge is at a slight angle, and when switching from one bolt to the other to measure is mirrored
• I made sure to have the gauge sit in the same position every time for the measurement, since it was never properly "centered" when hanging
• Values varied when the gauge moved, so I stuck with the lowest values I could see, but the range was always the same

I've tried researching potential issues, testing different amounts of lube applied on the threads and under-heads of the bolts (no difference), and cleaning the threads and bolts and re-applying the lube, etc., and nothing has worked so far. I'd love to finish this job up but I'm beginning to think that the stretch gauge is really only useful for when the engine is out and the gauge is in a normal vertical orientation, but I've seen others use the gauge underneath the vehicle too with no issues so either I am missing something or got a dud.

All that being said, I am going to contact ARP today and see what I can find out is wrong with my methodology, and if I can't find a resolution I'll stick with their 68 Nm suggestion for all the bolts, although it would make the gauge a very expensive paperweight. I was trying to be accurate and enjoy the process with this method but it's left me wishing I reverted back to the OE bolts as the 3 time torque sequence doesn't seem too bad to me now.

[Slideways]

Posted by Lang Racing on the old M3F:

S54 engines manufactured prior to 2003 come with larger rod bolt that are not supposed to be replaced according to BMW TIS. The later engines use a rod bolt that is smaller (torx head) and is one time use. On the early engines we prefer to use ARP fasteners because we don’t know the condition of the stock rod bolt. On the newer 2003+ engines we have found that the stock bolt is completely reliable and a bit cheaper than the ARP bolts so we will typically use those unless the customer requests ARP bolts. In our bench testing we found that the ARP bolt in the 2003 and newer engine needs to be stretched beyond the ARP specification to achieve the same bore shape as the stock BMW bolt.

A benefit of the ARP bolt design is that it allows us to use the rod stretch gauge to preload the fasteners. Because the rod bolt is arguably the most critical bolt in the engine, we like being able to use the most accurate method we can for tightening it. By using rod bolt stretch we have found that depending on conditions the torque can vary as much as 10ft lbs from fastener to fastener to achieve the same stretch. Using ARP hardware take slightly more time using the stretch method but we believe the peace of mind and longevity is worth it on the earlier engines. Another benefit of the ARP bolts is that they can be reused in the future instead of replacing them in the future. This is particularly useful on a track or race car that will be serviced frequently."

https://langracing.com/s54-rod-bearing-and-bolt-replacement-with-arp-fasteners/

https://nam3forum.com/forums/forum/main-forum/e46-2001-2006/91971-connecting-rod-bolts