Even the Most Reliable Used BMW M Cars Have Fixable Flaws

Reliable used BMW M car problem guide highlights:

  • VANOS upgrades are a common requirement for used BMW M cars, even the most reliable ones
  • Replacing plastic water pumps and other cooling-system parts with metal versions is also common
  • Although each used BMW M car recommended by experts at Enthusiast Auto Group has some flaws, they’re all fixable to some extent

Reliability is a virtue in any car, but it’s especially important for people looking to save money with used cars. And it’s downright vital when that used car is a BMW M product, given the potential repair bill. That doesn’t mean secondhand M cars are all disasters waiting to happen, though. However, it does mean that even some of the stoutest BMW M cars typically need some proactive wrenching.

What are the most reliable used BMW M cars?

A silver E39 BMW M5 parked on a road next to a forest
The E39 M5 is one of the most reliable used BMW M cars | BMW

MotorBiscuit’s guru in used BMW M cars is Ohio-based shop Enthusiast Auto Group. The shop has made an extensive name for itself when it comes to the Bavarian brand’s products. Matt Farah of The Smoking Tire, for example, recently purchased an E46 M3 from EAG and highly recommends its services.

I spoke with Mike Kent of EAG about BMW M reliability, and he recommends sticking to naturally-aspirated models from the brand’s “analog era.” In this case, that means cars from the late 1990s to roughly 2010 with either the S52 or S54 inline-six or the S62 V8. Or, in other words, one of the following models:

  • 2004-2006 E46 M3
  • 2006-2008 Z4 M Coupe/Roadster
  • 2000-2003 E39 M5
  • 1998-2002 Z3 M Coupe/Roadster
  • 1997-1999 E36 M3

Now, although these M cars are generally reliable, that’s dependent on regular maintenance. Thus, before you decide to buy, get a pre-purchase inspection and inspect any service records. Furthermore, these are still used cars; some are almost old enough to be classics. So, any examples you find for sale will likely have age-related issues like worn suspension components and old gaskets. Again, a PPI should let you know about these problems, which aren’t BMW-specific.

In addition, as with newer BMW models, even these used BMW M cars aren’t without their flaws. Fortunately, Kent assures me that BMW enjoys “a huge community when it comes to figuring out issues and figuring out solutions.” If you budget a bit of wrenching time and/or money, the remaining problems are fixable.

Once you get past the rod bearings, used 2004-2006 E46 BMW M3 ownership is mostly about maintenance—if you get the manual

The S54 inline-six engine in a blue E46 BMW M3 Convertible's engine bay
E46 BMW M3 S54 inline-six engine | BMW

US M fans will likely know that BMW introduced the E46 M3 here for the 2001 model year, not 2004. However, Kent recommends skipping the first few years because the S54 inline-six had some notable rod-bearing failures. Any 2001-2003 M3s still around now should have stronger replacements, but BMW Tuning says some flawed original bearings remain.

Once you get past the rod bearings, though, the 2004-2006 M3 is generally a reliable used BMW M car. Case in point, Kent has access to EAG’s fleet, but his daily driver is an E46 M3. However, you must be diligent with maintenance, especially oil changes and valve adjustments, he warns. In addition, valve adjustments usually involve replacing the valve cover gasket. And there are some flaws worth noting.

The “real Achille’s heel” of the S54 is the VANOS valve-timing system, Kent says. But today, rebuild kits provide “updated seals…upper timing chain guides, anti-rattle clips,” and similar stronger replacement parts, he notes. Get one of those kits or have a trusted BMW mechanic install it, and you’re good.

This used M car also suffers from another common BMW issue: water pump failure. Yet while replacing it is a bit tricky, BMW Tuning says, modern versions swap the fragile plastic components for metal ones. Do that, and the pump goes from a flaw to another long-term maintenance item.

One thing that doesn’t necessarily require addressing is the rear subframe. Unless it’s cracked and/or you want to track your E46 M3, EAG says you don’t have to reinforce it. But don’t get one with the SMG automated manual unless you want to “burn all your money,” Road & Track claims.

A used 2006-2008 BMW Z4 M might be a more reliable car than the E46

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The E46 M3 isn’t the only used BMW M car with the S54, though. BMW also put that engine in the 2006-2008 Z4 M Coupe/Roadster. And because it came after the rod bearing update, there’s one less problem to worry about. Admittedly, Z4 Ms with lots of track miles can have rod issues, PistonHeads says. However, a PPI and oil analysis will usually check for that.

Because it has an S54, Z4 Ms require regular valve adjustments. But these sports cars are also manual-only; no SMG headaches here. Just make sure that the car you’re looking at completed its running-in service, or it could suffer extra engine wear, PH warns. And again, upgrade the VANOS.

Some used BMW Z4 Ms can suffer head gasket and alternator failure, but those are rare issues that are mostly age-related. Also, the idle-control valve can get gummed up with carbon deposits, which isn’t unusual amongst direct-injection engines. Fortunately, removing carbon from engines is fairly straightforward.

Apart from the engine-specific issues, PH notes that Z4 Ms can develop cracks around their front strut mounts. However, it seems to be even less of an issue than the E46’s subframe cracks. In addition, the stiff ride can prematurely damage the stock aluminum engine mounts. Stronger steel replacements are readily available, though.

Other than that, though, a well-maintained used 2006-2008 BMW Z4 M is typically a reliable car.

Used 2000-2003 E39 M5s have one of BMW’s most reliable V8s, but they still need some help

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In general, Kent recommends going with inline-six engines if you’re buying used BMWs. However, if you want a V8, the 2000-2003 E39 M5 is your best bet for reliability and durability. Although the related M62 V8 isn’t a bad engine, Kent says the S62 has a better cooling system. So, it doesn’t suffer from heat-related plastic degradation, or at least not as much. And it’s a “really potent engine,” he says.

There are some downsides to getting the V8, though. No, it doesn’t require valve adjustments. But if something goes wrong, “there’s [sic] eight components as opposed to six,” Kent notes. And if the valve covers start leaking, the S62 has two of them rather than one. Basically, part costs are higher because it simply has more parts.

Still, while one R&T writer had some problems with a 190,000-mile example, the E39 M5 is generally stout. Kent recommends getting a later model with an updated VANOS system, though again, upgrade kits are available. Also, by now these used BMW M cars might need new gaskets and timing chains. And make sure the plastic chain guides get replaced with stronger versions.

Other than that, though, the only notable E39 M5 problems are carbon buildup, worn suspension bushings, and salt-induced rust, R&T reports. Some S62s suffered rod bearing failures, but nowhere near as frequently as S54s, BMW Tuning adds. An oil analysis should let you know if they’re failing.

Model years matter with a 1998-2002 Z3 M

A silver 1998 BMW Z3 M Coupe
1998 BMW Z3 M Coupe | National Motor Museum/Heritage Images/Getty Images

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Making reliability updates to a used BMW Z3 M Coupe/Roadster depends on which model year you have. 1998-2000 cars have S52 engines while 2001-2002 Z3 Ms have S54 engines. And yes, in addition to the other S54 issues, that means later Z3 Ms came with flawed rod bearings from the factory. So, if you want one of those cars, get a PPI and budget for upgraded bearings if they’re not already installed.

But if you really want a reliable used BMW M car, the S52 is where it’s at. It’s “the most robust set-it-and-forget-it…engine” you can get in an M product, Kent says. Admittedly, it’s not the most characterful M engine. However, apart from the VANOS system, it doesn’t have any significant flaws.

There are some spots to check, though. S52s consume some oil regularly, especially as they age. But if your engine is really burning oil, check the piston rings and PCV valve. Also, the Z3 M’s original radiator is plastic, which tends to crack with age, R&T notes. Replace it with a sturdier metal version. Same thing with the water pump and the plastic thermostat housing.

In addition, used BMW Z3 Ms might have cracked differential mounts, though you can weld in reinforcements. Some cars also develop sloppy shifters from worn return springs, PH adds. And if you want an M Roadster with a power top, make sure it works.

Still, regardless of the model year, a used BMW Z3 M can easily be reliable with a few upgrades.

It’s almost a classic, but a 1997-1999 E36 M3 can keep going with some upgrades

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The final entry on the list of reliable used BMW M cars is the near-classic E36 M3. Admittedly, the earliest ones are old enough to qualify for classic status. As such, these cars will likely require the most attention out of any on this list.

Still, there’s plenty to like about the E36 M3 from a reliability standpoint, especially the later models. As noted earlier, these use the S52 inline-six. So, provided you follow the maintenance schedule, upgrade the VANOS, replace plastic cooling system parts, and check the oil levels, this engine is stout. But absolutely make sure the sprocket keeping the chain-driven oil pump is securely fastened, or you’re out an engine, R&T says. And no, the transmission fluid is not a ‘lifetime’ fluid.

Aside from the engine, used 1997-1999 BMW E36 M3s mainly suffer from the usual age-related problems. Old rubber components, scattered rust pockets, and so on. Check the steering system for leaks, too. In addition, the E36 M3’s rear strut towers and rear trailing-arm bushing pocket often crack over time. Weld-in reinforcement plates are readily available, though. And avoid the convertible models—their roof mechanisms are complicated and expensive to fix, R&T reports.

Admittedly, that’s a lot of information to keep track of for those hunting down used BMW M cars. But don’t let this laundry list scare you off just yet. It might take some work, but these luxury sports cars can be daily drivers.

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