Used BMW Z4 review

Exterior

• If you’ve spent any time on forums or owner groups, you’ll already know that issues with the retractable roof motors on the convertible Z4 are well-documented. BMW, for some inexplicable reason, placed the motors in a location where they’re vulnerable to water exposure from blocked drainage channels. And, as you’d expect, water and electronics don’t mix well. Once the motor gets soaked, failure is inevitable. While some specialists can revive water-damaged motors, the best long-term fix is to relocate the motor to the boot, where it stays dry. There are excellent YouTube tutorials that guide you through the process, or if you prefer a low-tech solution, some owners have opted to ditch the electronic operation altogether and convert it into a manual-only roof mechanism.
• Speaking of drainage channels, like just about every convertible ever made, it’s critical to keep them clean and free of debris. The drainage holes above the rear wheels, in particular, can become clogged easily, and if left unchecked, water will eventually make its way into the cabin behind the front seats, leading to a whole host of potential issues.
• Obviously, the hardtop Z4 Coupe (E86) avoids these concerns entirely, but then you also miss out on the wind-in-your-hair experience and the occasional bug smashing into your face at speed.
• Regardless of whether you go for the Roadster or Coupe, one universal check applies: make sure all electrically powered functions are in working order. That includes central locking, windscreen wipers, power windows, and everything else running through the car’s electronics.
• If you notice anything operating sporadically or not at all, the culprit is often the GM5 module. A quick tip from owners’ groups—don’t bother going to a BMW dealership to fix this, as they’ll charge you a small fortune. Instead, forums like Z4Forum.com and E46Fanatics have plenty of advice on repairing or replacing the GM5 module, though if you do swap it out, you may need to have it re-coded.
• At this age, window regulators can also fail, so if the glass refuses to rise or lower smoothly, that’s a likely culprit.
• More mechanical exterior issues to be aware of include stretched Bowden cables in the doors, which can prevent them from opening properly, as well as worn-out door handle mechanisms.
• The same problem can affect the bonnet release cable—if it’s stretched or lacking lubrication, you might struggle to get the bonnet open at all.
• Speaking of the bonnet, inspect its alignment carefully. The hinge mechanism can be tricky to work with, and once misaligned, it’s not the easiest thing to set straight again.
• As for the lights, like many cars from this era, the headlight lenses can yellow over time, which is an easy fix with polishing kits. However, if you plan to do a lot of night driving, it’s best to avoid models equipped with halogen headlights. Plenty of owners claim that their phone’s flashlight does a better job of illuminating the road ahead. Instead, look for a Z4 fitted with the optional Xenon headlights, which offer significantly better visibility.

Interior

• Push every button. Try every switch. Does it work? Hopefully, yes—but don’t be surprised if you encounter a few electrical gremlins. Owners have reported everything from faulty air conditioning (which can be expensive to repair) to infotainment glitches. Fortunately, there aren’t too many electronics inside to go wrong, so the list of potential problems is relatively short.
• That said, some of the electrical issues can be more annoying than others. The seat occupancy sensor, for instance, is known to fail, which can trigger an airbag warning light. The airbag module itself is also known to be problematic, and it’s particularly vulnerable to any liquid spills inside the cabin. If it fails, expect to spend well over $1,000 to sort it out—so be extra careful with your coffee.
• Door handle issues are another common complaint, with some owners finding that the handles stick or simply refuse to open the door. Sometimes, a bit of lubrication can fix the problem; other times, you’ll need to replace the entire handle assembly.
• A worn handbrake mechanism is another frequently reported issue, but there’s plenty of advice on how to fix it available through Z4 owner groups and forums.
• One of the most common complaints with the Z4’s interior, however, is the tendency for plastic components to become brittle with age. This results in excessive rattles and squeaks, particularly in older models. It’s not just a noise issue—some cubbyhole doors can become stuck closed or even crack apart entirely over time.

Mechanically

M54B25 (2.5L) & M54B30 (3.0L)

• The M54 engines are generally well-regarded, but like all BMW inline-sixes, they come with a few well-known trouble spots.
• The water pump and thermostat housing can fail, and the best preventative measure is to replace them with high-quality aftermarket parts, which often last longer and cost less than BMW OEM replacements.
• Oil leaks from the valve cover gasket and oil filter housing are common, but they’re not catastrophic—just something to be aware of.
• One key component to check is the DISA valve, which alters the intake manifold airflow for optimal performance. The problem? It’s mostly plastic, and when it fails, you’ll likely notice a drop in power and torque, possibly accompanied by a rattling noise and fault codes. Worst-case scenario, if it disintegrates, pieces can get sucked into the engine. Fortunately, there are repair kits and upgraded replacements available at a reasonable price.
• VANOS solenoids (for both intake and exhaust) can develop minor issues, while the PCV valve can also cause complications, though neither is a major concern.
• At nearly 20 years old, many of these engines will also have brittle plastic engine bay components and a worn cooling system, so expect to replace hoses and expansion tanks sooner rather than later. The upside? Parts are relatively affordable compared to other BMWs.

N52B25 (2.5L) & N52B30 (3.0L)

• The N52 engines that came with the facelifted Z4 are widely regarded as some of BMW’s most reliable naturally aspirated petrol engines. However, they’re not without their quirks.
• Unlike the M54, the 3.0L N52 uses an electric water pump, which is notorious for failing—often suddenly and without warning. It’s not cheap to replace, but it’s best to do so preemptively around 100,000 km to avoid an unexpected failure.
• Valvetronic motor issues can arise, as can VANOS solenoid failures due to oil sludge buildup. You can try cleaning them, but most owners simply replace them when problems occur.
• Early versions of the N52 also had issues with hydraulic lifters that weren’t adequately lubricated, causing them to rattle (often described as a ticking noise). The problem worsens in poorly serviced engines, but most owners just live with the sound.
• As with the M54, oil leaks from the valve cover and oil filter housing are common, and by now, most of the plastic cooling system components will be nearing the end of their lifespan. Fortunately, complete replacement hose kits are available at reasonable prices.