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BMW Z4 Z4 Roadster sDrive18i common faults.

2013–2018, convertible, petrol, 156 HP.

The fault list covers: N20B20 engine, ZF8HP transmission.

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5 fault write-ups. 4 important. 2 recalls.

If you know the year, pick it. Faults for other years drop out of the list.

Before you buy

Known faults

4 important faults

critical2

N20 2.0 petrol: breaking timing chain guide

critical

The chain guide of the early N20 engines is brittle: if it breaks, the chain goes slack, and from then on the timing is imprecise. The symptom is initially a high pitched whistle or drone from the front of the engine that rises with the revs: many people take it for the supercharger or a pulley noise. Later a metallic rattle on a cold start joins it.

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The fault concentrates on engines built between 2012 and early 2015; after February 2015 they got an improved guide. In the 3 Series the 320i and the 328i are affected.

You can hear the noise before the chain jumps.

between 90,000 and 216,000 km

What to check

  • On a cold start stand at the front of the engine and listen to the first seconds: a metallic rattle is suspect
  • At idle, then applying throttle slowly, watch for the high pitched whistle or drone that rises with the revs
  • Do not accept "that is just the pulley" as an explanation: the noise is at the front, in the centre, and it rises with the revs, so it is not the pulley
2 more steps in the write-up

Oil pump chain: the plastic guide disintegrates and blocks the pickup

critical

The oil pump is driven by a separate, smaller chain from the crankshaft, behind the timing chain at the front of the engine. This chain runs on plastic guides, and under heat cycles the plastic cracks, flakes off and finally disintegrates. From then on the chain works against the aluminium, the tension is lost, and the stretch progresses fast.

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It causes damage along two paths, and the less known one comes first. The broken pieces of plastic are sucked into the oil pickup tube, block the way of the oil there, and destroy the bearings before the chain has even jumped. The other path is the chain or the tensioner letting go: then the oil pressure disappears within seconds, and the engine can seize without stopping.

The warning is not the lamp. This fault does not always light a warning, so the noise is what to listen for: between 1500 and 2500 revs a high, whistling whine comes from the lower part of the engine, and at a cold start a rattle of one to five seconds is audible. The maker issued its own service bulletin for the whining noise on the N20 and the N26.

On the factory chain the fault is reported above 80 000 miles, that is above roughly 129 000 kilometres, but in the American settlement the maker took it on earlier as well: below 70 000 miles, that is 113 000 kilometres, the full cost, and above 100 000 miles or eight years nothing at all. The affected set is the N20 and N26 engines built between 2012 and 2015.

The repair costs between 4000 and 6000 dollars, because the work on the timing and on the oil pump go together. If someone has replaced the timing chain, the oil pump chain has to be replaced with it: if the job is left half done, the engine has to come apart again in a few years.

above 129,000 km

What to check

  • Rev it to between 1500 and 2500 and listen to the bottom of the engine: a high, whistling noise points here
  • Start it cold and listen for a rattle of one to five seconds
  • Do not wait for a warning light: this fault does not always light a lamp
3 more steps in the write-up

expensive2

Oil filter housing gasket: oil leak onto the belt and the alternator

expensive

A rubber gasket seals the oil filter housing to the block. The gasket hardens over the years, and oil leaks from under the housing. The oil drips onto the drive belt and the alternator.

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Three things can happen. The oil stretches the belt and it can jump off (on a single belt engine that means an instant loss of the water pump and the alternator); oil getting into the alternator destroys the windings; and oil reaching the hot exhaust smokes and gives a burnt smell, and the official complaints do include burning smells and smoke.

The leak is visible: five minutes on a lift settles it. The gasket itself is a cheap part; the labour, the ruined belt and the alternator take the money.

between 64,000 and 246,000 kmreported complaints only

What to check

  • On a lift look at the block surface around the oil filter housing: a wet, oily or oily dusty film
  • Look at the drive belt: an oily, cracked, stretched belt is the consequence of the leak
  • Look at the alternator housing from below: an oil trail indicates damage reaching the windings
2 more steps in the write-up

ZF 8HP automatic: mechatronics unit and connector sleeve leak

expensive

The ZF eight speed automatic (BMW Steptronic 8HP family) has two faults, and you can feel both.

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The first is the mechatronics unit: the valve body and the control electronics in one. If the solenoids or the pressure regulation weaken, the gearbox jerks, the D/R engagement is delayed, it logs a gear ratio fault code, and finally drops into limp mode (often staying in 2nd or 3rd).

The second, and often misdiagnosed, is the connector sleeve of the mechatronics unit: the O-ring of the plastic sleeve ages, and ATF leaks from the side of the housing, exactly where the wiring harness enters. This is easy to mistake for a rear crankshaft seal. The trail starts from the driver's side of the housing, not from the clutch side.

On cars built in 2023 there was also a separate safety recall for a welding fault in the mechatronics unit. That is not the same as the wear related sleeve and the valves.

Check the fluid level, the area around the sleeve and the fault codes first; do not accept a "full gearbox replacement" quote straight away.

above 120,000 km

What to check

  • On the test drive watch for delayed D/R engagement, a jerk when shifting, and limp mode (a stuck gear)
  • Look at the driver's side of the gearbox housing where the wiring harness enters: an ATF trail from the sleeve is suspect
  • Do not confuse it with a rear crankshaft seal leak: the direction of the trail decides
3 more steps in the write-up

cheap repair1

Plastic charge pipe: it goes brittle and cracks at the throttle body

cheap repair

The maker builds the charge pipe out of plastic, and the coupler at the throttle body is the critical point. The material goes brittle from heat cycles, from boost pressure and from the heat of the engine bay, and then it cracks. Three things coincide here: the moulded coupler carries both pressure and movement, the vibration of the engine arrives here through the throttle body, and the spot gets continuous heat load. The crack starts on the inner radius of the coupler. The symptom is a loss of pressure under load: the engine pulls cleanly at part throttle but flattens out at full throttle, and a hissing noise is audible from the engine bay at the same time. A yellow drivetrain warning comes with it, which often disappears after a restart, and sometimes a brief limp mode. One thing is worth knowing: a clean fault memory does not rule the crack out. The pipe has no sensor of its own, so the control unit can only log a boost pressure fault, and the leak is intermittent, appearing only under load. At a viewing two things are visible without tools. On the inner radius of the coupler the hairline crack sometimes comes with dark staining, because the oil mist in the boost air escapes through it. For the same reason a greasy, dark ring can appear at the joint of the coupler. The crack is reported above 80 000 kilometres, and replacing the pipe costs between 100 and 400 euros, because the part itself is not expensive. The most common misdiagnosis against that is replacing the turbocharger, which costs an order of magnitude more, and a pressure test protects against it. The factory repair is the same plastic part, which can crack again at a similar mileage; replaced with an aluminium pipe this failure mode disappears, and the driveability does not change.

above 80,000 km100–400 EUR

What to check

  • Look at the inner radius of the coupler at the throttle body: the hairline crack sometimes comes with dark staining
  • Look for a greasy, dark ring at the joint of the coupler
  • On a motorway slip road at full throttle watch for the loss of pressure and the hissing noise
2 more steps in the write-up

Checklist

BMW Z4 Z4 Roadster sDrive18i

First what you would check on any car. Then the faults of this model.

Before you buy

Checklist

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On every car

Ask the owner

Faults of this model

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Official recall2 recallsShow

The manufacturer fixes these for free at a franchised dealer. Ask with the VIN whether it was done.

Most recent: 13 August 2024

24V608000ENGINE AND ENGINE COOLING:COOLING SYSTEM:PUMPENGINE AND ENGINE COOLING:COOLING SYSTEM:PUMP13 August 2024 · NHTSA (USA)

BMW of North America, LLC. (BMW) is recalling certain 2012-2015 X1 sDrive28i, X1 xDrive28i, 2012-2016 Z4 sDrive28i, 528i, 528i xDrive, 328i, 328xi, 2016-2018 X5 xdrive 40e, 2014-2016 228i, 228xi, 428i, 428i xDrive, 328xi Gran Turismo, 2013-2017 X3 sDrive28i, X3 xDrive28i, 2015-2018 X4 xDrive28i, 2015-2016 428xi vehicles. An improperly sealed electrical connector on the water pump may be exposed to water and short circuit.

Risk: An electrical short increases the risk of a fire.

Remedy: Dealers will inspect and replace the water pump and plug connector as necessary, and install a protective shield, free of charge. Owner notification letters were mailed on March 28, 2025. Owners may contact BMW customer service at 1-800-525-7417.

The authority's notice

SR/03830/25Safety recallFireno date · EU Safety Gate

Water may come into contact with the starter relay and gradually cause corrosion. This could affect the electrical connection inside the relay and make the engine difficult to start. It may also result in a short circuit and could cause the starter to overheat leading to a fire when the vehicle is in motion or when it is parked with the ignition off. The product does not comply with the Regulation on the approval and market surveillance of motor vehicles and their trailers, and of systems, components and separate technical units intended for such vehicles.

Remedy: Type of economic operator taking notified measure(s): Manufacturer Category of measure(s): Recall of the product from end users Date of entry into force: Unknown

The authority's notice

Engine and transmission

N20B20

115–180 kW (156–245 HP) · petrol

Model year2011–2017

ZF8HP · 8-speed automatic, longitudinal (ZF 8HP45/50/51)

automatic · 8 speed

Torque limit500 Nm
MakerZF

We built the code from the model and the gear count. The factory sheet does not state it.

Variant data

What is in this version

Factory data

Trim
Z4 Roadster sDrive18i
Body
convertible
Fuel
petrol
Transmission
automatic
Engine size
1997 cc
Power
115 kW (156 HP)
Drive
RWD
Production
2013–2018

Factory service interval

The manufacturer specifies this for this version. Of the mileage and the time, the one that comes first is the one that counts.

  • Air filter

    • 60,000 km or 4 years

  • Cabin (pollen) filter

    • 30,000 km or 2 years

  • Brake fluid change

    • first: 3 years, then 2 years(first change at 3 years, then every two years)

  • Engine oil and oil filter (BMW condition-based service)

    • LongLife25,000 km or 2 years

  • Automatic gearbox oil (ZF 8HP / 6HP)

    • 160,000 km

  • Spark plugs, petrol

    • 60,000 km or 6 years
All E89 versions

Information, not an expert opinion

We write the descriptions, and we put the source next to them. A person reviews them before they go out. They are still information, not a technical expert opinion.

  • A fault on the list does not mean the car you are looking at has it.
  • A fault missing from the list does not mean the model is fault-free. Write-ups are made model by model. Not all of them are done.
  • You decide whether to buy. This is no substitute for an inspection. That needs a workshop and a history check.
Details in the terms