BMW Z4 buying guide
BMW took quite a gamble with the design of its Z4, but it was one that paid off. You can profit from it, too… if you choose
Everything you need to know before you buy one.
After the relatively svelte Z3, the first-generation Z4 – unveiled in 2002, with UK sales beginning in 2003 – looked radical. Gone was the conventional design and in came ‘flame surfacing’ with a mix of curves and angled shut lines, courtesy of designer Anders Warming, overseen by Chris Bangle. The Z4’s bodyshell was more than twice as stiff as its predecessor’s to reduce scuttle shake, and the handling was aided by sophisticated multi-link rear suspension system. Now you can buy a Z4 from just £3000 – here’s how to ensure it’s a good ’un.
The Z4 range is more convoluted than you might think, with some engines changing at the time of a mid-life facelift in 2006. Entry-level cars got a 150bhp 2.0 four-cylinder engine; above this were 170bhp 2.2 or 192bhp 2.5-litre six-pot units. At the top of the regular range was a 231bhp 3.0-litre straight-six. In 2006 the cosmetic facelift also introduced updated engines with 215bhp 2.5-litre Si and 261bhp 3.0-litre Si units replacing the previous engines of the same capacity.
The Alpina Roadster S with its 300bhp 3.4-litre straight-six ceased production at the same time as the ferocious 343bhp Z4M was offered in 2006, with a 3.2-litre six-cylinder engine; Alpina cars are about as rare as Z4MS. While the Z4M is the most thrilling to drive and the most collectible, it’ll also be the costliest to run. Assuming you’re not buying a Z4 to use every day we’d suggest avoiding the sometimes troublesome four-cylinder cars, as part of the appeal is the smooth sound of the straight-six.
Any Z4 with a six-cylinder engine is hugely appealing; the bigger the engine the more relaxing it is to drive, with the 2.2-litre unit providing a great balance of performance and economy.
All Z4s got a manual gearbox as standard, generally with six speeds but sometimes with five in the smaller, pre-facelift engines. Some engines were also available with automatic transmission, again, usually with six gears but occasionally with five in the pre-facelift cars. The auto options were Steptronic (a ZF five/six-speeder with torque converter) or SMG (also known as SSG by BMW), the latter being an automated six-speed manual gearbox. The regular auto box turns the Z4 into a great cruiser but the SMG polarises opinions more. It’s not the same unit seen in the contemporary M3 and it’s not as slick, so don’t buy an Smg-equipped Z4 without thoroughly trying it out first.
Most Z4s have some options fitted but few have a lot of them. Those worth seeking out include heated seats and xenon lights. Bluetooth and cruise control can also be useful, while sports seats are more comfortable than the regular chairs; sports seats are easy to source and fit though. The factory-fit navigation works well, but hi-fi upgrades aren’t possible if this is fitted – the same goes for the DSP (Digital Sound Processor) option.
Corrosion shouldn’t be an issue on any Z4. If there are any signs of rust it’s almost certainly because of poorly repaired crash damage, so do an HPI check and inspect the panel gaps closely; they should be tight and even. Parking sensors were available only at the rear, which is why front damage is common.
The expansive bonnet is made of aluminium and it can get dented by stones. The cheapest fix will be to buy a used bonnet and (if necessary) get it repainted, but if you can buy one in the right colour you might get away with spending as little as £200.
Look for signs of damage to the front and
rear bumpers, which are large and get scraped. If a replacement front bumper is needed the bill can easily run to £1000 with painting and fitting. Buy a used one, fit it yourself and it’ll be closer to £200.
If an electrically operated roof is fitted you need to check it works properly. The motor that controls everything gets flooded, if the previous owner failed to clear the roof drains. The motor housing can be modified or moved to alleviate the problem. Budget £600 or more to get the problem fixed at a BMW dealer but there are lots of forum enthusiasts who could help fix the problem for far less.
Engine faults are relatively unusual. Any engine that’s not running properly should be plugged into a diagnostic computer which should pinpoint any problems. It’s worth investing in a small handheld scanner or ELMS327 Bluetooth module that plugs into the OBD2 socket above your feet and links to an app on your phone; the car is clever enough to produce a code and tell you what’s wrong, potentially saving garage costs.
If the 2.0, 2.5 Si and 3.0 Si engines get a bit too warm for comfort it’s probably because the electric water pump is on its way out. It’s not the end of the world if you have to replace one; expect to pay £250 for a new one, fitted.
The Z4’s running gear was taken from the E46 3-series, which means there’s a ready supply of parts and used engines. The variable intake manifold (DISA valve) can fail, given away by a rattle
from the manifold once the plastic components have broken up; there will also be a lack of top-end power or low-end torque (or both), depending on the position in which it has failed. Camshaft sensors also fail, betrayed by hesitation and the engine being sluggish to start when warm. It’s an easy DIY fix but stick with genuine BMW parts as pattern sensors tend not to be as robust.
The 2.0-litre engines (the only four-cylinder unit fitted to the Z4) are susceptible to stretched timing chains, so listen for a slapping noise as the engine is started; once things are set to get expensive a warning light will illuminate on the dash. Much of the problem is caused by weak tensioner guides that are made of plastic. These powerplants can also suffer from a failed head gasket, so be prepared to spend £750 on putting things right. The 2.2, 2.5 and 3.0-litre engines can use oil; officially a litre of lubricant every 1000 miles is fine. If you see visible smoke on start up or when accelerating hard it could be a split crankcase ventilation (CCV) valve or a sticking piston oil control ring. An aftermarket CCV kit is less than £50, although access beneath the inlet manifold is a bit tight; a product such as Seafoam helps free the oil ring. Some owners go a step further by replacing the CCV with an aftermarket pressure control valve (PCV) and catch can, which often helps reduce oil consumption. Any car still on its original suspension is likely to
‘Trim fixes tend to be DIY, but a marque expert will be quicker’
need some TLC by now, not least of all because the rear springs are prone to breaking, given away by knocking as the car is driven; sometimes the car sits low at one corner. It’s not a costly problem to fix (budget £300 for both sides), but when you’re getting the work done it’s worth also replacing the rear damper mounts.
Expect wear in the front control arms and ball joints, leading to vague steering, while creaking from the front may be down to the diagonal front strut braces working loose. If the rear suspension wanders about on bumps it’s probably because the bushes in the trailing arms are in need of replacement; budget £200 to put things right.
It’s worth getting a four-wheel alignment check done, especially if anything in the suspension has been replaced. Vagueness is sometimes attributed to the electric power steering fitted to all Z4s (the Z4M got a hydraulic system), but it’s rare.
The electric PAS can suffer from stiffness, the cure for which can be as simple as lubricating the universal joints or adjusting the ring that controls the electric motor/column. The worst-case scenario is a new rack, which costs £2700 if you go for a new one. You can save cash by opting for a used rack, but you won’t know how much life is left in it.
Brake problems only crop up on cars that have been driven hard, and even then, the extent of any issues should be just worn discs and pads. M models have E46 M3 CSL brakes, with front discs costing around £340 for a pair.
Run-flat tyres were fitted to all Z4s apart from the Z4M and Alpina Roadster S which got conventional rubber. It’s not unusual to find a Z4 that’s been switched to regular tyres, as these are cheaper and provide a more comfortable ride. Because there’s no space for a spare wheel you’ll have to settle for a can of sealant and a compressor instead, but many owners reckon this is a compromise worth making.
Trim and electrics
The Z4 is essentially very well built, but squeaks and rattles aren’t rare. It’s possible to eliminate them but this is best done on a DIY basis, as it tends to be time consuming; it’s largely trial and error. A marque expert might be able to fix things faster if they’ve come across specific problems before.
The headlights could be the weedy halogens or the brighter and more effective xenons. Xenon lights can be identified by their lack of cockpit height adjustment wheel. Neither is prone to problems but if the latter is fitted make sure they function properly, including the self-levelling system – if this doesn’t work an MOT failure is guaranteed. With replacement xenon headlights priced at around £600 you really don’t want to have to replace one.
If items such as the electric windows, wipers or central locking are playing up it’s probably a failure of the GM5 module which sits behind the glovebox. It’s cheap enough to fix as just two relays in the module have to be replaced but check the main battery first as once this starts to fail it can produce the same symptoms. Incidentally, not allowing the battery to go flat is a good idea (invest in a conditioner if necessary). If it has gone flat and the car has been left in transport mode from new (the ECU should have been updated so this mode is deleted rather than disabled), the car might refuse to run properly.
MaintenanceAll Z4 engines are chain driven, so there are no cambelts to replace. Expect to use a litre of oil every 1000 miles. They’re all fairly easy to work on.
NomenclatureThe Z4 Roadster MKI carries the BMW codename E85; the Coupé is E86.
DoorsHandles can stick in the open position, but lube should fix things.
ECUSTo access the GM5 unit (see text), the glovebox has to be dropped down.
WipersArms sometimes don’t park correctly; clean and lubricate the mechanism.
Faults can be picked up by diagnostics.