AFTER THE relatively svelte Z3, the first-generation Z4 Ė unveiled in 2002, with sales beginning in 2003 Ė looked radical. Gone was the conventional design and in came Ďflame surfacingí with a mix of curves and angled shut lines, courtesy of designer Anders Warming, overseen by Chris Bangle. The Z4ís bodyshell was more than twice as stiff as its predecessorís to reduce scuttle shake, and the handling was aided by sophisticated multi-link rear suspension. These days, you can buy one of these cars from just $10,000 Ė hereís how to ensure itís a good íun.
Engines ranged from underpowered fours (overseas) to naturally aspirated and turbo straight sixes with power levels from as low as 110kW all the way up to 252kW for the Z4M.
All Z4s got a manual gearbox as standard, generally with six speeds, but sometimes with five. Some engines were also available with an auto, again, usually with five or six gears. 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.
BODYWORK Corrosion shouldnít be an issue on any Z4. If there are any signs of rust itís almost certainly because of poorly repaired crash damage, so inspect the panel gaps closely; they should be tight and even throughout.
The expansive bonnet is made of aluminium and can get dented by stones. The cheapest fix will be to buy a used bonnet and (if necessary) get it repainted. 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 $1800 with painting and fitting.
If an electrically operated roof is fitted you need to check it works properly. The motor that controls everything gets flooded if a previous owner failed to clear the roof drains. The motor housing can be modified or moved to alleviate the problem. Budget $1100 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.
The Z4 may be a two-seater, but it isn't impractical. Thereís ample space for touring, the seats are comfy and refinement is great too. The only drawback is the firm ride. They're easy to work on Ė access to most bits is good and few special tools are needed so you can run a Z4 surprisingly cheaply.
1. NAILS THE BASICS It's a front-engined, rear- wheel drive layout with an atmo BMW inline six Ė yes, please
2. M POWER Using parts from the E46 3 Series, the Z4M nabbed the M3 powerplant for 252kW/365Nm
3. HARD TOP If you don't like the idea of topless motoring, the Z4 can also be had as a coupe
OILY BITS Engine faults are relatively unusual. Any engine thatís not running properly should be plugged into a diagnostic computer which should pinpoint any problems.
If the 2.0, 2.5 Si and 3.0 Si engines get too warm for comfort itís probably because the electric water pump is on its way out. The Z4ís running gear was taken from the E46 3 Series, which means thereís 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 Ė stick with genuine BMW parts as pattern sensors tend not to be as robust.
The 2.5- and 3.0-litre engines can use oil; officially a litre of lubricant every 1600km 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.
Any car still on its original suspension is likely to 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. Itís not a costly problem to fix, but when youíre getting the work done itís 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 itís probably because the bushes in the trailing arms need replacing.
Itís worth getting a wheel alignment, 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 itís 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 around $4500 new.
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.
Run-flat tyres were fitted to all Z4s apart from the Z4M. Itís not unusual to find a Z4 thatís been switched to regular tyres, as these are cheaper and provide a more comfortable ride. Because thereís no space for a spare wheel youíll have to settle for a can of sealant and a compressor instead.
TRIM AND ELECTRICS The Z4 is essentially very well built, but squeaks and rattles arenít rare. Itís possible to eliminate them, but this is best done on a DIY basis.
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. Neither is prone to problems but if the latter is fitted make sure they function properly, including the self-levelling system. With replacement xenon headlights priced at around $1100 you really donít want to have to replace one.
If items such as the electric windows, wipers or central locking are playing up itís probably a failure of the GM5 module which sits behind the glovebox. Itís 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. 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.
Buy wisely and the Z4 is great drop-top fun.