BMW rod bearings: What is the real story here?

What’s one thing S54 owners worry about? That’s right, rod bearings: Are they good or are they about to fail and wipe out the entire engine?

[E46-chassis BMW M3 | Buyer's Guide]

Gulp.

We’ve had this in the back of our mind ever since we bought our 2004 BMW M3. Even though the car sported plenty of documentation, was built after BMW’s mid-run update, and came from an old friend, we didn’t know the history of its rod bearings.

The odometer showed 138,000 miles. Surely they had been done at some point, right? (Right?)

That was the one question mark always hanging over this car. And, we admit, it kept us from fully enjoying it. It’s hard to spin a rather pricey, 8000 rpm engine to the redline when you’re unsure about its health.

Oil analysis and physical inspections didn’t reveal any looming trouble, either–no warning signs, no noises. Still, we felt it was time to replace those rod bearings.

A lot of the info found on the internet regarding E46 M3 rod bearings seems to have been posted at least a decade ago, however, so we asked James Clay, president of BimmerWorld, if there was anything new to report.

James has been our spiritual guide for this project, from initial inspection to countless late-night texts. Plus, he knows BMWs and has owned more than one E46 M3.

During the E46 M3’s model run, there was a production split: pre- and post-recall. “It was considered the solution,” he says.

“What we know with certainty now is that S54–and similar engines found in the future models, the S65 and S85–need rod bearing attention as part of general maintenance, recall or not,” he continues.

“Rod bearing issues are more prone to affect higher-load engines–something routinely revving over 7000 rpm.” He says this discussion should also extend to later BMW engines like the S65 and S85, and he expects it to also impact modern, big-boost engines like the N54, N55 and S55.

“A majority of wear is caused in startup and warmup,” he explains. “Properly warming up your engine seems to notably reduce bearing wear.

“A proper engine oil with high sheer strength–I look for a Group V full-synthetic, PAO-ester base like Red Line–will help on both startup and high revs.”

More questions for James: Are there any signs for when it’s time to replace the bearings, and can an oil analysis help?

“One oil analysis can’t help,” he explains, noting that “a trend over a span of time and seeing the trend suddenly change can. On the street, I’ve heard them make rod noise before they damage the crank, but that’s a small window. And on the track, you likely don’t get that warning.

“That being said, it’s about $800 of parts for a premium bearing and oil, or a $2000 job at full pop with labor, and I feel like if you’re going to own one of these cars, you just plan on it at some point.”

How often should you replace rod bearings? “For a road car,” he says, “if I bought one with over 70K miles and it wasn’t already documented as being done, I would inspect and/or do them. If I bought a car from myself with scheduled oil changes with Red Line and a proper warmup on the engine before driving, I’d feel very comfortable with 100,000 to 120,000 miles before looking at them–not that I put that many miles on these cars.

“And I guess that’s the real thing: At this point, I don't know that many people intend to stack miles on these cars, so doing it once when you get it for peace of mind for the duration of ownership is probably worth it.

“I do treat track cars differently, because when an engine goes at the track, it’s going to go fast and it’s going to be at least a full engine replacement typically, if not some additional damage due to dropping oil in that environment–for yourself or, even worse, for others.

“I never ever pass up an opportunity when an engine is out of the car or the oil pan is accessible to take a look at the rod bearings. I may not always replace them, but I take a look and replace the rod bolts. Then I like to replace them every two years or 100 hours or so on full-race engines. They can likely go twice as long or more–again, with the right warmup and the right oil–but the risk of damage is just too high to not be more proactive.”

Our car was built after the 2003 update. Does that matter? “Nope,” James tells us. “Or it matters minimally. It was, in effect, a great way to put new bearings in cars–on the update–to get them further down the road.

“Just like the reason you’re asking about two flavors of S54–and I’m saying those flavors don’t matter–and what does are the revs. The ’03 update is minutiae.”

Driving style matters, he stresses: “The real issue is people jumping in cars and putting the throttle down, and maybe to some degree doing the included maintenance thing–not sure when that started–but definitely not using the premium oils.

“Take care of the car,” he continues. “BMW put in the dynamic rev indicator lights so when the car is cold it shows yellow lights around 5K rpm to limit people from pounding on the car when cold–and when most damage occurs.

“That is not enough. To me, aside from using a high-sheer-strength oil like Red Line or some other true Group V base, warming the engine means a good 3 to 5 minutes at idle after starting. Then I don’t pay attention only to rpm or that moving rpm yellow limit light. I care more about load I put into the engine, so I keep throttle below 30% to 50%, and I definitely keep rpm below 3000 to 4000 rpm until I hit about 170 Fahrenheit. Then I start leaning into it.

“That means I don’t drive these cars when I’m late to work, but I think for most people that’s not the use of these cars anymore anyway. They are special. Take your time. They’ll appreciate it.”

Phil Wurz, BimmerWorld’s sales and operation manager, notes how each engine is unique. “Not to cause alarm to the hundreds of thousands–millions?–of N55 engines that are found in so many BMWs. I did rod bearings on my wife’s X5 at about 165K miles, and they had a little wear but were in decent shape,” he says.

“If I had a crystal ball, I wouldn’t have changed them, but really I was just curious,” he continues. “Of course, this is a car that rarely sees over 4500 rpm. Also, while we didn’t buy it new, under our ownership it has followed the standard BimmerWorld practice of a Red Line oil and to properly warm the car up in the winter.

“On the other side,” he continues, “our F82 M4 GTMore project car with an S55 engine seemed to have a track-abused life before we got our hands on it. It was unknown how many track miles it had, but we know the odometer showed over 50K. We did bearings preventatively and, sure enough, there was some copper showing on the bearings.”

Spoiler alert: We finally decided to replace the rod bearings. As James stresses, it’s part of the ownership experience, and you can only kick that can so far down the road.

We figured that you get one shot at this job. Mess it up and, well, now you’re looking at an engine rebuild–or worse–and these engines aren’t exactly common.

We wanted to have an expert do the work.

Fortunately, the engine doesn’t have to come out of the car for this service. The front subframe must be dropped so the oil pan can be pulled, but the entire procedure can be done from below: Remove bearing caps, remove bearings, replacing bearings, fit new rod bolts, torque to spec, reassemble everything.

While in theory the front suspension will go back together as it was, we were advised to get an alignment afterward.

[Fresh Red Line Fluids for Our High-Revving M3]

We called a few local BMW shops, and they were too busy or just not interested in the job. Rennie Bryant at Red Line Bimmer Performance said his shop regularly replaces rod bearings, but South Florida is a bit of a hike from our home base near Daytona Beach.

Sometimes the answer is hiding under your nose. Auto Clinic of Ormond has been servicing our staff’s cars for years–project cars and just regular cars–and has done this job before.

In fact, the shop had recently done another S54 engine. It’s located about 10 minutes away, so the folks there put us on the schedule.

Now to gather parts.

We turned to BimmerWorld for our parts order, and the shop recommended rod bearings from BE-Clevite. “A few years back, the BE Bearing option came onto the scene,” Phil explains. “The issue they were trying to remedy with their bearing solution was to open up the tolerance relative to the BMW bearings.

“The BMW bearings have always been a bit on the tighter tolerance side versus some others, so that factors into the wear rate of the bearings to a certain extent,” he continues. “The BE Bearings making the tolerance just a touch larger helps improve the lifespan of the bearings. The BE Bearings also have a coating on them to help in low oil–initial startup–and clearance scenarios, and they’re also a tri-metal shell design that can handle much higher loads to withstand the abuse of the higher-revving S54.”

A set retails for about $400.

Where you buy bearings–and, really, any other critical parts–also matters. As Phil tells us, BimmerWorld has rejected bearings from another supplier that didn’t pass muster. That company’s warehouse, located near the coast, supplied bearings sporting some surface rust. Those bearings were turned away.

What about our main bearings? Something else to worry about? No, James says.

“To me,” he says, “mains aren’t an inherent wear issue. Off the cuff, rod bearings are replaced 10:1 over mains, and most mains that get replaced are ‘while you’re there.’ But if you ever see a damage pattern indicating trash went through the oil passage when replacing the rod bearings, it’s worth a peek at the mains also.”

We also needed rod bolts. BimmerWorld says that the ARP pieces are 10 times stronger than the stock ones, so that’s what we ordered.

The ARP catalog shows two different part numbers for the S54 engine, however. As ours was built after February 2003, we’d need ARP part No. 201-6102–about $113 from BimmerWorld.

The rest of the job doesn’t need much regarding parts: just an oil pan gasket, oil filter and a few quarts of Red Line Oil. Like the bearings and bolts, these parts can also be found in the BimmerWorld catalog. (By the way, BimmerWorld carries Red Line for non-BMWs, so it has 10W30 for your Miata.)

We dropped off the M3 at Auto Clinic on a Monday morning. Its technicians said we’d see the car by the end of the week.

“End of the week” must mean “end of the next day” in their world. Even while stopping so we could take photos, they had the car ready for us by EOD the following day.

A casual look showed that the bearings didn’t appear too worn. No copper showing through.

Could they have gone another 10,000 miles? We guess the answer depends on how much you like to gamble.

The inside of the engine looked just as clean as the outside. No issues at all were found during the service.

While the car was there, we also had Auto Clinic replace the VANOS line with an upgraded piece from BimmerWorld. After a while, these lines can weep a bit.

The work order shows that replacing the rod bearings took 12 hours. Multiply that by your shop’s hourly rate to get an idea for a likely bill. In very round numbers, like James says, this was a $2000 service once adding in the price of the bearings, rod bolts, oil and gaskets.

When we bought our M3, it was a $10,000 car. Today, well, you can easily double that figure for an example this clean. And at the rate we drive the car, the bearings are now good for a decade or three.

One last step to complete the job: After getting some gas as advised, we took the car back to Alignment Shop, Inc., for an alignment–same specs as before.

So what’s next for our BMW M3 now that we’ve addressed two of the big three issues with these cars–subframe mounts and rod bearings? How about we drive it and enjoy it?

Next, though, we should take a closer look at the third item on that list: the VANOS system.

Hello, BimmerWorld, mind a little more hand-holding?

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