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

Practical Classics (UK) - - CONTENTS -

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.

Which one?

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.

Body­work

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.

Oily bits

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.

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