BMW Z4 Z4 Roadster sDrive30i common faults.

2019–2022, convertible, petrol, 258 HP.

The fault list covers: B46B20B, B48B20O1 engine, ZF8HP transmission.

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6 fault write-ups. 5 important. 11 recalls.

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

Before you buy

Known faults

5 important faults

critical2

B48 and B38 petrol: the timing chain guide rail breaks

critical

Plastic guide rails hold the timing chain in place. On these engines the plasticiser in the plastic leaches out over time, the rail turns brittle and then breaks into pieces. The pieces land around the chain and further down, in the oil sump and on the strainer of the oil pump, and the leached plasticiser also deposits on that strainer. Two kinds of damage come from this: without its guide the chain starts to flap, and less oil reaches the engine through the narrowing strainer. The first sign is a rattling noise on a cold start that goes quiet after a few seconds or once the engine has warmed up. It is heard best on a fully cold start in the morning, because the chain tensioner needs time to tension the chain. The problem is reported above 60,000 km. Replacing the chain costs between 700 and 2,900 euro, and is typically four figures, because the chain can only be reached by removing several engine components.

above 60,000 km700–2,900 EUR

What to check

Start the engine fully cold in the morning and listen for the rattling noise
Ask whether the chain and the guide rail have been replaced, and ask for the invoice
Ask when the oil was last changed and how often the car was serviced

2 more steps in the write-up

Electric water pump: silent failure, immediate overheating

critical

In these engines the water pump is not belt driven but has its own electric motor. It gains on fuel consumption, but it opens a new failure path: the pump or its electronics often simply stops with no warning. Measured in the official complaints, the typical mileage is 161,000 km (a tenth of the complaints already at 81,000, a tenth only above 257,000 km). So the common wisdom of "around 100,000 km" is early: most of the failures happen between 130,000 and 250,000 km.

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With a belt driven pump the flow weakens gradually, here the circulation stops in an instant. In urban traffic the temperature crosses the limit within minutes, the cylinder head distorts, and the repair is an engine rebuild.

Replacing a still good pump at around 120,000 to 150,000 km costs less than repairing an overheated engine. If the replacement is already in the service book, the pump has already been changed.

between 81,000 and 257,000 km

What to check

Watch the coolant temperature gauge after startup: it should settle evenly, not jump around
Standing still with a warm engine, listen for whether the cooling fan and the pump are working
Ask for a fault code read: codes pointing at coolant flow belong here

2 more steps in the write-up

expensive3

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

Crankcase ventilation (CCV) in the valve cover: oil consumption, rough running

expensive

The crankcase ventilation leads the gas that forms in the crankcase back to the intake and separates the oil out of it on the way. If the system clogs or the membrane tears, the pressure cannot get away: it finds a way out past the seals, or it pushes the oil through the piston rings. This is where the oil consumption comes from, and the oil that appears around the valve cover gasket. In the other direction a faulty breather takes unmetered air into the intake, and that is what makes the idle rough, the throttle response hesitant and the running coarse. Starting also gets harder, and in an extreme case the engine stalls at idle. Two characteristic signs help: weak or absent suction at the oil filler with the engine running, and noticeably rough running around 3,000 rpm. The hose at the rear of the valve cover can also let oil out. The sound insulation then soaks itself with oil, and oil gets everywhere in the engine bay. On the six-cylinder engines the breather is built into the valve cover, so the repair is replacing the cover or the whole oil separator together with the hoses, between 80 and 900 euro.

between 80,000 and 150,000 km80–900 EUR

What to check

With the engine running unscrew the oil filler cap: weak or absent suction is a sign
Look around the valve cover and at the rear of the engine bay for oil traces
Watch the idle, and the rough running around 3,000 rpm

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

Official recall11 recallsShow

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

Most recent: 23 September 2025

25V636000ELECTRICAL SYSTEM:STARTER ASSEMBLY:RELAYELECTRICAL SYSTEM:STARTER ASSEMBLY:RELAY23 September 2025 · NHTSA (USA)

BMW of North America, LLC (BMW) is recalling certain 2019-2021 BMW 330i, 2019-2022 BMW Z4, 2020-2022 BMW 530i, X3, X4, Toyota Supra, 2021-2022 BMW 430i, 430i Convertible, and 2022 BMW 230i vehicles. The engine starter relay may corrode, causing the relay to overheat and short circuit.

Risk: A short circuit in the starter relay may increase the risk of a fire.

Remedy: Owners are advised to park their vehicles outside and away from structures until the remedy is complete. Dealers will replace the engine starter, free of charge. Owner notification letters were mailed February 6, 2026. Owners may contact BMW customer service at 1-800-525-7417. Vehicle Identification Numbers (VINs) involved in this recall became searchable on NHTSA.gov November 14, 2025.

The authority's notice

21V598000ENGINEENGINE2 August 2021 · NHTSA (USA)

BMW of North America, LLC (BMW) is recalling certain 2020 M340i, M340i xDrive, 540i, 540i xDrive, X3 M40i, 2020-2021 X4 M40i, 745Le xDrive, 2019-2021 Z4 M40i, and 2020-2021 Toyota Supra vehicles. During engine start, the engine management software may cause loss of braking assist. Full mechanical braking (without assist) remains available.

Risk: Loss of braking assist can increase the risk of a crash.

Remedy: Dealers will update the engine management software, free of charge. Owner notification letters were mailed on September 17, 2021. Owners may contact BMW customer service at 1-800-525-7417.

The authority's notice

20V516000EXTERIOR LIGHTING:HEADLIGHTSEXTERIOR LIGHTING:HEADLIGHTS27 August 2020 · NHTSA (USA)

BMW of North America, LLC (BMW) is recalling certain 2019-2020 Z4 sDrive30i, Z4 M40i and 2020 Toyota Supra vehicles. The headlamps are able to be adjusted horizontally. As such, these vehicles fail to comply with the requirements of Federal Motor Vehicle Safety Standard number 108, "Lamps, Reflective Devices and Associated Equipment."

Risk: Should the headlamps be adjusted horizontally, there could be increased glare and reduced visibility for oncoming drivers, or reduced visibility for the vehicle operator, thereby increasing the risk of a crash.

Remedy: BMW will notify owners, and dealers will inspect the headlamp vertical and horizontal adjustment plugs, correcting them as necessary, free of charge. The recall began December 23, 2020. BMW owners may contact BMW customer service at 1-800-525-7417 or Toyota owners may contact Toyota customer service at 1-888-270-9371.

The authority's notice

20V355000STEERING:LINKAGES:TIE ROD ASSEMBLYSTEERING:LINKAGES:TIE ROD ASSEMBLY15 June 2020 · NHTSA (USA)

BMW of North America, LLC (BMW) is recalling certain 2019 Z4 sDrive30i, 2019-2020 330i xDrive, M340i and M340i xDrive, 2020 X3M and X4M, and Toyota Supra vehicles. In certain driving conditions, such as high temperatures and rough road surfaces, a steering gear tie rod may become damaged, possibly resulting in a fractured tie rod.

Risk: A damaged or fractured tie rod may affect vehicle handling and control, increasing the risk of a crash.

Remedy: BMW and Toyota will notify owners, and dealers will replace the steering gear tie rods, free of charge. The recall began August 14, 2020. Owners may contact BMW customer service at 1-800-525-7417 or Toyota customer service at 1-888-270-9371.

The authority's notice

19V732000ENGINEENGINE15 October 2019 · NHTSA (USA)

BMW of North America, LLC (BMW) is recalling certain 2019-2020 330i, 330i xDrive, and 2019 Z4 vehicles. The needle roller bearings of the counterbalance shafts may have been improperly installed, potentially causing the counterbalance shaft to loosen.

Risk: If the counterbalance shaft loosens, severe engine damage could occur, increasing the risk of a crash.

Remedy: BMW will notify owners, and dealers will replace the engine, free of charge. The recall began December 13, 2019. Owners may contact BMW customer service at 1-800-525-7417.

The authority's notice

19V684000BACK OVER PREVENTION: SENSING SYSTEM: CAMERABACK OVER PREVENTION: SENSING SYSTEM: CAMERA27 September 2019 · NHTSA (USA)

BMW of North America, LLC (BMW) is recalling certain 2018 540d, 2018-2020 530i, 530i xDrive, 540i, 540i xDrive, M550i xDrive, M5, 530e, 530e xDrive, X3 sDrive, X3 xDrive, X3 M40i, X3 M, and 2019-2020 X4 xDrive, X4 M40i, X4 M, X7 xDrive, X7 M50i, 740Li, 740Li xDrive, 750Li, 750Li xDrive, 8 Series Convertible and Coupe 840i, 840i xDrive, M850i xDrive, X5 sDrive, X5 xDrive, X5 M50i, X6 xDrive, X6 M50i, 330i, 330i xDrive, M340i, M340i xDrive, Z4 sDrive, Z4 M40i, 740Le xDrive and 745Le xDrive, 2018-2019 640i xDrive Gran Turismo and Rolls-Royce Phantom, 2019 M850i xDrive Gran Coupe and Rolls-Royce Cullinan and 2020 Toyota Supra vehicles. The back-up camera and display settings can be adjusted such that the rear view image is no longer visible and the system will retain that setting the next time the vehicle is placed in reverse. As such, these vehicles fail to comply with the requirements of Federal Motor Vehicle Safety Standard (FMVSS) number 111, "Rearview Mirrors."

Risk: The lack of an image in the back-up camera display increases the risk of a crash.

Remedy: BMW will notify owners, and dealers will update the back-up camera software, free of charge. The recall began November 8, 2019. Owners may contact BMW customer service at 1-800-525-7417 or Rolls-Royce at 1-877-877-3735. Toyota owners may contact Toyota customer service at 1-888-270-9371.

The authority's notice

A12/00031/20Safety recallInjuriesno date · EU Safety Gate

The headlight control unit may have been damaged in the course of the supplier’s production process. This could result in a short circuit in the control unit, causing the headlights, headlamp illumination or the turn-signals to fail, increasing the risk of an accident.