S54 baffle upgrade

[Michael.p]

Hi everyone,




I have an E46 M3 sedan with the S54 engine. I replaced the rod bearings with ACL bearings about 3 months ago, and after around 1,700 km of break-in, the bearings failed again.




After starting to research the issue, I came across upgrades like an S54 oil pan baffle and related oiling improvements.




At this point, I’m starting to lose confidence in the engine. The car is my daily driver, so I’m trying to understand if these upgrades are actually important for reliability, and what can realistically be done to improve the engine’s durability.




Also, I’d like to know what the correct break-in procedure should be after rod bearing replacement, and how many kilometers are recommended.




Any advice would be appreciated.

[Obioban]

Did you check the crank and rods? Why did you replace them the first time (did you spin one)?

What you're experiencing is not normal, and therefore wont' be fixed by mods. The S54 has a pretty great oiling system stock. An engine with good crank/rods (hasn't spun/damaged them) is good for a LONG time with factory bearings/bolts. For a DD/street use, factory bearings with factory bolts, on a health engine with correct install, are good for 100,000+ miles. 200,000 if you don't routinely hit redline (as in, Z3M with 7500rpm redline s54 doesn't really wear out rod bearings ever).

Break in also isn't going to solve your problem. Either your crank/rods are damage, the bearings you installed were faulty/wrong spec, or the install was bad.

[Michael.p]

You're probably right that something else could be going on, but to be fully honest — I didn't follow a proper break-in procedure.

After installing the ACL bearings, I drove the car harder than I should have during the first ~1,500 km, including some aggressive driving . I now understand that was a mistake, especially for fresh bearings.

So before I assume it's purely an install or clearance issue, I want to make sure I do things properly this time.

What would you recommend as a correct break-in procedure for rod bearings on an S54?

- RPM limits?
- Load vs. no load?
- How long before full throttle is safe?

Appreciate your input.

[Obioban]

You're probably right that something else could be going on, but to be fully honest — I didn't follow a proper break-in procedure.

After installing the ACL bearings, I drove the car harder than I should have during the first ~1,500 km, including some aggressive driving . I now understand that was a mistake, especially for fresh bearings.

So before I assume it's purely an install or clearance issue, I want to make sure I do things properly this time.

What would you recommend as a correct break-in procedure for rod bearings on an S54?

- RPM limits?
- Load vs. no load?
- How long before full throttle is safe?

Appreciate your input.

There's a lot of contention around the best break in procedure, including some people thinking driving it really hard from the get go. Harder than it can be driven on the street.

I don't agree with them (I follow BMW's procedure), but the fact that it's a discussion means engines aren't blowing up immediately on people that do that.

Your issue is one of 3:
damage to the engine outside the bearings
wrong/bad parts installed
bad install

[Obioban]

Again reiterating this this is NOT the cause of your issue, BMW's S54 break in procedure after installing new rod bearings is for 1200 miles:
<5500 RPM
<100 mph
<2/3 throttle
vary engine speed often (don't sit on the highway in a gear)

Then oil change.

If you replace the bearings with the same parts/technique, you will have the same problem after following this procedure.

[bigjae46]

Break-in procedure is not the problem. What I commonly see when someone spins new bearings is the bearings were replaced due to a low end noise. The person tried to cheap out and swapped in new bearings.

Have you checked the bearings to make sure the rod bearings are indeed the failure?