Home » The Popular BMW B58 Inline-Six Engine Has One Big Achilles Heel

The Popular BMW B58 Inline-Six Engine Has One Big Achilles Heel

Bmw M340i Achilles Heel
ADVERTISEMENT

The BMW B58 inline-six is a darling of the European car tuning scene. With a closed deck block, forged connecting rods, and a forged crankshaft, it seemed like BMW finally learned from its N54 direct-injected boosted-six stumbling block and created a juggernaut. However, to long-time BMW owners, one question lingered — how would BMW, um, BMW the B58 up? Well, it turns out that some of these boosted sixes are suffering from serious oiling system issues at relatively low mileage.

Make no mistake, the B58 is an absolute beast of an engine, capable of slingshotting a 3 Series from zero-to-60 mph in under four seconds, and willing to crank out more than 400 horsepower to the tires with simple bolt-ons and a tune. It’s been available under the hood of just about every BMW on a longitudinal platform in the past few years, and this single-turbo three-liter inline-six is as smooth as you could possibly want. However, earlier examples of the B58 have one achilles heel because BMW decided to make the oil pump rotor housing out of plastic.

Vidframe Min Top
Vidframe Min Bottom

In theory, this was a great idea. Plastic is less thermally conductive than steel or aluminum, lightweight, and could reduce parasitic losses. Unfortunately, plastic also gets brittle with age and in cold temperatures, and as oil tends to thicken in the cold, you can probably guess what happens next.

G-series B58 owners in cold climates – check your oil pumps! We’ve had two almost new cars in our shop since february with blown engines due to the oil pump failing in freezing conditions. BMW have made an updated oil pump which replaces duoplex plastic with metal. The pictures speak for themself????
byu/mariusrisan inBMW

Yeah, that’s pretty gnarly. Oil pump failure is something you never want to encounter, and to make matters stranger, symptoms for a failed oil pump on older B58 engines run the gamut. Some report excessive oil pressure, some report insufficient oil pressure, some simply report a whining sound. The common thread? If you let any of these symptoms go for too long, you could be saying goodbye to your engine.

ADVERTISEMENT

Screenshot 2024 06 14 At 9.48.10 am

According to the forums, being unable to check oil level through iDrive when the oil is hot is a fairly solid symptom of oil pump issues, as dramatic fluctuations in pressure will lead to the test automatically being canceled due to the self-testing function requiring tight tolerances in the oil pump.

Screenshot 2024 06 14 At 10.34.27 am

As for affected models, they’re all over the map, but failures do seem to be most common on BMW’s crossovers, specifically vehicles like mid-2020 production and earlier X5s and X7s. However, early G20 M340i owners aren’t immune either. Many 2019 and 2020 examples without the high-performance cooling and tire package (option code ZTK) came with an oil pump featuring a plastic rotor housing, and owners have reported oil pump failure, sometimes with fewer than 30,000 miles on the clock. Curiously, the ZTK oil pump, part number 11419895359, has superseded the old regular oil pump, indicating that models newer than 2020 may not have this issue.

Weirdly, all this talk about oil pump failure is somewhat reminiscent of oil pump nut failure on M54 engine of the early 2000s, except a bit worse. In those engines, the nut holding the oil pump drive sprocket would back out under prolonged enthusiastic driving, with catastrophic results. On the B58, the failure mode is a little different, but the end result could be the same.

ADVERTISEMENT

Screenshot 2024 06 14 At 10.32.08 am

Alright, so let’s say that you own a B58-powered BMW that’s out of warranty and want to get this issue fixed. Figure around $1,200 in parts, but as replacement requires dropping the subframe, labor won’t be cheap. One poster on Bimmerpost was quoted $6,000 for oil pump replacement in their X5, and it’s easy to see why, given how the B58 places its timing components on the back of the engine, and the oil pump is driven by the timing system. Regardless of dealer service or saving money and going to an independent specialist, this isn’t a cheap fix, being financially up into what used to be M car repair territory. Ouch.

So, if you own a 2020 or older BMW with the B58 inline-six or are looking at one as your next daily driver, you might want to keep an eye on your oil pump. Failures seem widespread enough to render this a relatively common issue, and it wouldn’t be surprising if this becomes the modern BMW equivalent of Porsche’s infamous IMS bearing.

(Photo credits: BMW, Bimmerpost)

Support our mission of championing car culture by becoming an Official Autopian Member.

ADVERTISEMENT

Relatedbar

Got a hot tip? Send it to us here. Or check out the stories on our homepage.

Share on facebook
Facebook
Share on whatsapp
WhatsApp
Share on twitter
Twitter
Share on linkedin
LinkedIn
Share on reddit
Reddit
Subscribe
Notify of
64 Comments
Inline Feedbacks
View all comments
Fasterlivingmagazine
Fasterlivingmagazine
24 days ago

When i worked at the dealership, i regularly went to training down at bmw’s headquarters in new jersey. When i asked people who worked there about bmw’s quality issues i got the same answer every time. Basically that bmw builds cars for the first owner that owns it during the warranty period and screw anybody who owns it afterwards.

Turbotictac
Turbotictac
25 days ago

My coworker has one, I recommended doing an ownership delete

Thomas Metcalf
Thomas Metcalf
25 days ago

It is like BMW builds engines to the warranty period and not a second longer. Somebody HAD to have raised the thought that plastic ages poorly, especially in heat/cool cycling.

Davey
Davey
25 days ago

As someone who owned one of those N54 engines, it amazed me then how much stuff was plastic that shouldn’t have been. The cost cutting (sorry, BMW would say weight savings) was evident everywhere and made me realize that these cars are built to be leased for 3 years, not owned. They’re even priced like that.
That car ultimately ruined BMW for me, for the rest of my life. It amazes me how the longer some companies make things, the quality doesn’t actually improve (looking at you also, Wrangler).

Robert Runyon
Robert Runyon
27 days ago

If you own one don’t let them pull a Hyundai and blame the driver. I can see it now, “You didn’t check the oil” .Then you get to sue, and that’s fun too. Buy something else cuz life is too short for crappy engineering and lawyers. Or is that crappy lawyers and engineers?

Last edited 27 days ago by Robert Runyon
Matti Sillanpää
Matti Sillanpää
26 days ago
Reply to  Robert Runyon

I think that might backfire. I don’t think any BMW engine these days has dipstick :D.

Ron888
Ron888
27 days ago

“In theory, this was a great idea. Plastic is less thermally conductive than steel or aluminum, lightweight, and could reduce parasitic losses”

Why would you want an oil pump that’s not thermally conductive? How would that ever help anything? Weight saving and parasitic losses would be meaningless as well.
A plastic pump sounds like a risk from the get-go! I cant imagine what BMW were thinking.

TOSSABL
TOSSABL
26 days ago
Reply to  Ron888

I’m thinking along the lines of, “We’ve been using plastic water pumps for years—and they’ve been GREAT!”

Ross Fuller
Ross Fuller
21 days ago
Reply to  TOSSABL

composite water pump impellers are far superior to metal ones and cost more, not less, money to manufacture – application matters.

TOSSABL
TOSSABL
20 days ago
Reply to  Ross Fuller

I don’t dispute that.
But, as a long time shitbox buyer, when I buy a 150k, $1k car, I much prefer honest metal. 🙂

Turbotictac
Turbotictac
25 days ago
Reply to  Ron888

Nothing about that read as a good thing to me either

Danny Zabolotny
Danny Zabolotny
28 days ago

Here at the dealership we’ve replaced one B58 in an X5 recently due to one cylinder randomly losing compression, that was interesting.

In the hotter climate we have here in Arizona, we haven’t seen too many oiling issues with the B58, but we have seen a TON of cooling system issues. Darn plastic cooling system hoses keep leaking/breaking before the cars are even out of warranty. The all-plastic oil filter housings like to fail as well, along with the plastic coolant neck that goes on the block. Decent amount of water pumps failing on those engines too, but at least they’re cheap-ish due to being conventional belt-driven pumps again. Same exact issues as the B46/B48.

Manuel Verissimo
Manuel Verissimo
27 days ago

So the issues that existed on the M54 are still there 20 years later. Kudos BMW

64
0
Would love your thoughts, please comment.x
()
x