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BMW2013–2025 Critical issues documented

BMW 4 Series: common faults & what to check

Thinking about buying a used BMW 4 Series (2013–2025) in New Zealand? We've documented 20 known faults for this model spanning engine, cooling, electrical, and interior. Each researched and verified before it's published. The most serious issues here are rated critical. Every one is listed below with its symptoms and repair cost, and each has its own page with where to look and what to ask the seller. Free, no account needed.

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  • Odometer history
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  • NZ owned and operated

Type the plate for the free basics. The full record is a paid check from $13.49, one car at a time, no subscription.

No NZ plate yet, or buying in Australia? Pick the generation and engine and start a free check below. New to KickTyres? How the check works →

20

Documented faults

Critical

Most serious

$500–$2,200

Typical repair

52

Service milestones

Which BMW 4 Series are you looking at?

2 generation variants documented. Pick the shape you recognise: the faults, the servicing and the timeline below all narrow to it. Free, no account needed.

Now narrow it to the engine

A 1.8 and a 2.4 of the same car do not fail the same way, so the faults below narrow to the engine as well as the year. Free, no account needed.

Which engine is in it? These cover every year of this model.

420i428i430i435i440i420d430d435d

Start your free check on this BMW 4 Series

No plate needed. You get the risk score, the buyer's checklist and the guided inspection for the exact car you picked above — not the whole nameplate.

BMW 4 SeriesEngine not picked yet

Pick the engine above first: the 4 Series came with 8, and without it the report has to show all of their faults. Pick the engine

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Can't confirm for this car

BMW 4 Series

Nothing has been narrowed yet, so nothing below is a claim about a particular car. Pick a year and an engine to see which faults apply.

Tell us the engine, or check the engine code on the car, before relying on this.

matched on no vehicle context

What to look out for

The checks worth doing on a BMW 4 Series before you hand over any money. Every documented fault is listed below, each with its own page.

  • Serious issue

    This one is decided on a cold start, so insist the car has not been run that day and be standing there when the key is first turned.

    See why

    N20 2.0T timing chain guide and tensioner failure (420i/428i)

    The four-cylinder N20 in the 420i and 428i drives its timing chain off the crankshaft through plastic guide rails, with a second chain driving the oil pump. On engines built before BMW's revised parts arrived the guides go brittle and break up, the chain stretches, and the engine either sets a camshaft correlation fault or jumps timing and bends the valves. The oil-pump drive chain on the same end of the engine can also fail, which starves the engine of oil with no warning at all. This is the single most expensive thing that can go wrong with an early 4 Series, and the noise that gives it away lasts only a few seconds after a cold start.

    What you would notice

    • Rattle or whirring from the front of the engine for a few seconds after a cold start
    • Engine warning light with a camshaft/crankshaft correlation complaint
    • Loss of power, rough running, or a refusal to restart
    • Oil pressure warning immediately before a failure
    • Plastic fragments found in the sump or oil filter at a service

    Typically $3,000–$12,000 to put right.

  • Serious issue

    Cold-start the engine and listen carefully for chain rattle from the engine lower/rear area.

    See why

    B47 diesel timing chain and tensioner failure

    The B47 2.0-litre diesel used in 418d, 420d and 425d is afflicted by a documented timing chain stretch and tensioner failure pattern, predominantly at the rear of the engine where the chain is driven from the rear of the crankshaft. Cold-start chain rattle progresses to jumped timing and catastrophic engine damage if not addressed. BMW issued a recall in several European markets. The repair requires transmission removal, making it a significant labour job.

    What you would notice

    • Rattling noise on cold start from rear of engine, may clear after warm-up
    • Persistent chain rattle at idle that does not clear
    • Check Engine light with camshaft-crankshaft correlation fault codes
    • Engine stall or sudden loss of power if chain jumps

    Typically $3,500–$8,000 to put right.

  • Costly issue

    With the engine idling, listen at the top of the engine for a whistle or squeal that is not the belt.

    See why

    B58 valve cover PCV diaphragm failure and valve cover gasket leak (440i)

    The first-generation B58 (B58A) builds its crankcase ventilation (PCV) valve into the plastic valve cover, using a spring-loaded rubber diaphragm to control crankcase pressure. The diaphragm wears or tears, which lets oily vapour into the intake and can cause whistling, rough idle, smoke and higher oil use; separately the valve cover gasket hardens and seeps oil. BMW sells a diaphragm repair kit for the B58A, but many cars end up with a whole new valve cover. Owner reports on Bimmerpost include a 340i needing a valve cover and oil separator for a smoking exhaust.

    What you would notice

    • Whistle or squeal from the engine at idle
    • Rough idle or misfire
    • Blue or white smoke from the exhaust, worst on start-up
    • Oil seeping around the valve cover or burning oil smell
    • Oil level dropping between services

    Typically $300–$2,500 to put right.

  • Costly issue

    Observe cold-start behaviour on first crank.

    See why

    N55 high-pressure fuel pump (HPFP) failure

    The N55 3.0T single-turbo engine in the 435i is susceptible to high-pressure fuel pump failure, a known pattern carried over from the N54. The pump's internal roller follower mechanism wears against the camshaft lobe, causing fuelling instability. BMW extended warranty coverage in some markets following widespread failures. Aftermarket upgraded roller follower units are widely available as a preventive repair.

    What you would notice

    • Hard cold starts with longer-than-normal cranking
    • Rough idle and misfires under light throttle
    • Hesitation or stumble during acceleration
    • Fault codes P0087, P1093 or P0191 (fuel rail pressure below specification)

    Typically $1,200–$2,300 to put right.

  • Costly issue

    With the engine cold, check the coolant expansion tank level against the marks and look at the tank and its cap for cracks or dried residue.

    See why

    B58 coolant loss from plastic hoses, expansion tank and thermostat seals (440i)

    The first-generation B58 in the 440i relies on a lot of plastic in its cooling system: the expansion tank and cap, the vent hoses to the tank, the quick-connect hose joints and the O-ring seal on the thermostat (heat management) module. As the plastic ages and the seals harden, owners report slow coolant loss and low coolant warnings, often with no obvious puddle because the leak evaporates on the hot engine. Specialist workshops single out the plastic hose connector behind the heat management module as a frequent culprit. Caught early it is a hose, seal or tank; ignored, the engine can overheat.

    What you would notice

    • Low coolant warning on the dash
    • Sweet coolant smell after driving
    • White or pink crusty residue around hose joints or the expansion tank
    • Temperature reading or heater behaving erratically

    Typically $250–$1,800 to put right.

  • Costly issue

    Remove engine undertray and inspect oil cooler housing on the right-hand side of the block for oil staining.

    See why

    B48 oil cooler gasket leak

    The B48 2.0T engine uses a thermoplastic oil-to-coolant heat exchanger mounted on the block. The integrated gasket and O-ring seals degrade with thermal cycling, causing engine oil to weep into coolant or externally at the cooler housing. Documented across 3 Series, 4 Series and X3/X4 with B48. Common after 80,000 km. The B48 replaced the N20 in the 420i/430i from the 2016 LCI onwards and continues into the G22 generation.

    What you would notice

    • Oil in coolant reservoir (brown or milky tinge on cap underside)
    • External oil seepage around oil cooler housing area below the oil filter
    • Coolant consumption without visible external leak
    • Gradual oil level drop with no obvious drips on ground

    Typically $600–$1,300 to put right.

BMW 4 Series service schedule

What falls due, and at what distance, for each generation of the BMW 4 Series. These are the model’s intervals — the car’s own service book is the only thing that can tell you what has actually been done to it.

G26 4 Series Gran Coupe · 2022–2026 · Electric Motor (i4 eDrive35)

Electric

Due by distance

  1. 20,000 km

    Initial cabin filter and brake fluid flush check.

  2. 40,000 km

    Full vehicle health check including inspection of the high-voltage battery cooling system.

  3. 60,000 km

    Check suspension components and tyre wear due to the instant torque characteristics of the electric drivetrain.

G22/G23/G26 4 Series Coupe/Convertible/Gran Coupe · 2021–2026 · 3.0L S58B30 TwinTurbo (M4 Competition)

Petrol

Due by distance

  1. 40,000 km

    Major service inspection including spark plug assessment if the car has been driven aggressively.

  2. 60,000 km

    Replace the differential fluid and do a full brake fluid flush for optimal track or road performance.

  3. 80,000 km

    Recommended interval for a transmission fluid service and cooling system hoses inspection for long-term reliability.

G22/G23/G26 4 Series Coupe/Convertible/Gran Coupe · 2021–2026 · 3.0L S58B30 TwinTurbo (M4 Competition xDrive)

Petrol

Due by distance

  1. 20,000 km

    Initial running-in service completion is vital for the S58 engine longevity.

  2. 60,000 km

    Full inspection of drivetrain mounts and a fluid flush for the xDrive transfer case.

  3. 100,000 km

    Review the condition of cooling system components and auxiliary belt tensioners.

G26 4 Series Gran Coupe · 2021–2026 · Electric Motor (i4 eDrive40)

Electric

Due by distance

  1. 30,000 km

    A general health check and cabin air filter replacement keep the interior atmosphere fresh.

  2. 60,000 km

    Have the brake fluid flushed and the underside inspected for debris or road-salt impact, common for Kiwi driving conditions.

  3. 90,000 km

    Have a specialist assess the cooling system efficiency for the high-voltage battery to keep it at peak thermal performance.

G26 4 Series Gran Coupe · 2021–2026 · Dual Electric Motors (i4 M50 xDrive)

Electric

Due by distance

  1. 30,000 km

    Initial brake fluid flush and cabin microfilter replacement.

  2. 60,000 km

    Comprehensive inspection of the high-voltage cable connectors and charging port housing.

  3. 90,000 km

    Coolant system diagnostic check for the battery thermal management loops.

  4. 120,000 km

    General chassis health check covering the steering rack and suspension bushings.

G22/G23/G26 4 Series Coupe/Convertible/Gran Coupe · 2020–2026 · 2.0L B48B20 TwinPower Turbo (430i)

Petrol

Due by distance

  1. 60,000 km

    Proactive transmission fluid flush keeps the ZF 8-speed shifting smoothly.

  2. 80,000 km

    Watch coolant housing integrity, as plastic cooling components can become brittle over time.

  3. 100,000 km

    Assess the condition of the suspension bushings and dampers to maintain the crisp handling these models are known for.

G22/G23/G26 4 Series Coupe/Convertible/Gran Coupe · 2020–2026 · 2.0L B48B20 TwinPower Turbo (420i)

Petrol

Due by distance

  1. 60,000 km

    Proactive transmission fluid flush worth doing, even though BMW describes the oil as 'lifetime', for longevity on NZ roads.

  2. 80,000 km

    Check the condition of the auxiliary water pump and coolant hoses, as the B48 engine runs at high temperatures.

  3. 100,000 km

    Inspect the condition of the engine mounts, which can soften and cause slight vibration at idle.

G22/G23/G26 4 Series Coupe/Convertible/Gran Coupe · 2020–2026 · 3.0L B58B30 Mild Hybrid (M440i xDrive)

Petrol/Hybrid

Due by distance

  1. 40,000 km

    Full brake fluid flush and a visual inspection of the suspension bushings.

  2. 60,000 km

    Change the transmission fluid and filter to keep the ZF 8-speed's famously smooth shifting.

  3. 80,000 km

    Comprehensive inspection of the cooling system components and water pump housing, common practice for the B58 engine at this interval.

F32/F33/F36 4 Series Coupe/Convertible/Gran Coupe (LCI) · 2016–2020 · 2.0L B48B20 TwinPower Turbo (420i)

Petrol

Due by distance

  1. 60,000 km

    Proactive transmission fluid flush keeps the ZF gearbox crisp for years to come.

  2. 80,000 km

    Have the auxiliary cooling system inspected for any minor leaks.

  3. 100,000 km

    Plan for a suspension refresh, specifically looking at the front control arm bushings, which may start to soften.

F32/F33/F36 4 Series Coupe/Convertible/Gran Coupe (LCI) · 2016–2020 · 2.0L B48B20 TwinPower Turbo (430i)

Petrol

Due by distance

  1. 60,000 km

    Spark plugs and a fresh engine air filter are recommended to maintain that TwinPower Turbo efficiency.

  2. 80,000 km

    Inspect the auxiliary drive belt and tensioner to keep everything quiet and functional.

  3. 100,000 km

    Often considered the 'refresh' stage; many owners have the transmission fluid and filter kit replaced to keep the ZF gearbox shifting like new.

F32/F33/F36 4 Series Coupe/Convertible/Gran Coupe (LCI) · 2016–2020 · 2.0L B47D20 Turbo (420d)

Diesel

Due by distance

  1. 100,000 km

    Proactive transmission fluid flush and differential oil change.

  2. 120,000 km

    Monitor the DPF (Diesel Particulate Filter) pressure sensor readings during your service check.

  3. 150,000 km

    Review the condition of the auxiliary belt tensioner and cooling system plastic components.

F32/F33/F36 4 Series Coupe/Convertible/Gran Coupe (LCI) · 2016–2020 · 3.0L B58B30 TwinPower Turbo (440i)

Petrol

Due by distance

  1. 60,000 km

    Spark plugs are due for replacement, keeping that B58 engine running smooth as silk.

  2. 80,000 km

    Check the condition of the serpentine belt and tensioner to prevent accessory drive issues.

  3. 100,000 km

    Have a professional check the water pump and thermostat; preventive maintenance here supports long-term ownership.

F32/F33/F36 4 Series Coupe/Convertible/Gran Coupe · 2014–2016 · 2.0L N47D20 Turbo (420d)

Diesel

Due by distance

  1. 100,000 km

    Confirm the 'lifetime' transmission fluid is inspected and check suspension components like control arm bushings for wear.

  2. 150,000 km

    Peripheral engine components like the alternator or starter motor may warrant a friendly check-up by your local mechanic.

  3. 200,000 km

    Have a specialist verify the condition of the DPF (Diesel Particulate Filter) to ensure it is still regenerating efficiently.

F32/F33/F36 4 Series Coupe/Convertible/Gran Coupe · 2014–2020 · 3.0L S55B30 TwinTurbo (M4)

Petrol

Due by distance

  1. 60,000 km

    Inspect suspension bushings and coolant hoses for signs of age-related degradation.

  2. 100,000 km

    Consider replacing the spark plugs and checking the health of the crank hub bolt, a known point of discussion in the community.

  3. 120,000 km

    Ensure the water pump and auxiliary belt components have been inspected for reliability.

F32/F33/F36 4 Series Coupe/Convertible/Gran Coupe · 2013–2016 · 2.0L N20B20 TwinPower Turbo (420i)

Petrol

Due by distance

  1. 80,000 km

    Full inspection of the cooling system, including plastic hoses and the electric water pump.

  2. 100,000 km

    An ideal time to assess the condition of the turbocharger actuator and surrounding oil lines.

  3. 120,000 km

    The interval where suspension bushings and engine mounts benefit from a professional technician's assessment.

F32/F33/F36 4 Series Coupe/Convertible/Gran Coupe · 2013–2016 · 2.0L N20B20 TwinPower Turbo (428i)

Petrol

Due by distance

  1. 80,000 km

    Proactive check of the cooling system components and serpentine belt tensioner.

  2. 100,000 km

    The timing chain assembly draws attention from many owners at this stage; a professional inspection is often a wise investment.

  3. 120,000 km

    Optimal time to consider a transmission fluid and filter service to maintain that legendary ZF smoothness.

F32/F33/F36 4 Series Coupe/Convertible/Gran Coupe · 2013–2016 · 3.0L N55B30 TwinPower Turbo (435i)

Petrol

Due by distance

  1. 80,000 km

    Full cooling system refresh worth considering, as plastic components may begin to show age-related fatigue.

  2. 100,000 km

    The water pump and thermostat are often addressed around this interval to ensure continued reliability.

  3. 120,000 km

    Check the condition of the turbocharger vacuum lines and charge pipe to keep boost pressures consistent.

See all 20 documented issuesEverything researched for the BMW 4 Series, including 5 rated critical.
Depends on which engine this BMW 4 Series has — 20Each of these is documented for one particular engine. Pick the year and engine above to see which of them apply.
Engine, transmission & cooling12

01N20 2.0T timing chain guide and tensioner failure (420i/428i)

This one is decided on a cold start, so insist the car has not been run that day and be standing there when the key is first turned.petrol2014–2016EngineRead the full fault: symptoms, where to look, what to ask the seller

02B47 diesel timing chain and tensioner failure

Cold-start the engine and listen carefully for chain rattle from the engine lower/rear area.diesel2014–2020Engine
OccasionalEngine $3,500–$8,000 to fix

Can't confirm for this car

The B47 2.0-litre diesel used in 418d, 420d and 425d is afflicted by a documented timing chain stretch and tensioner failure pattern, predominantly at the rear of the engine where the chain is driven from the rear of the crankshaft. Cold-start chain rattle progresses to jumped timing and catastrophic engine damage if not addressed. BMW issued a recall in several European markets. The repair requires transmission removal, making it a significant labour job.

The front of a dual overhead camshaft engine with the timing cover removed, exposing the timing chain and sprockets.Example of the part — not this vehicle

The front of a twin-cam engine with the timing cover off — chain, sprockets and guides.

Logansenf · CC BY-SA 4.0 · Wikimedia Commons

Symptoms to notice

  • Rattling noise on cold start from rear of engine, may clear after warm-up
  • Persistent chain rattle at idle that does not clear
  • Check Engine light with camshaft-crankshaft correlation fault codes
  • Engine stall or sudden loss of power if chain jumps

What to check

Cold-start the engine and listen carefully for chain rattle from the engine lower/rear area. Check for fault codes relating to cam timing. Review full service history and ask whether chain or tensioner has been inspected. Diesel 4 Series are less common in NZ but more prevalent in AU market.

Where to look: Timing chain at rear of B47 engine block (transmission-side), chain tensioner and plastic guide rails

Parts involved: Timing chain.

Ask the seller

  • “Has the timing chain been inspected or replaced?”
  • “Does the engine rattle on cold start before it warms up?”
  • “Has it been serviced at correct intervals using correct oil viscosity?”

03Electric coolant pump seizure — overheating with no warning (N20/N55 420i/428i/435i)

petrol2013–2020CoolingRead the full fault: symptoms, where to look, what to ask the seller

04B58 timing chain cold-start rattle and tensioner wear

Cold-start the engine and listen for chain rattle at the front of the engine.petrol2020 onwardEngine
OccasionalEngine $1,800–$5,000 to fix

Can't confirm for this car

The B58 3.0T engine in the 440i and M440i can exhibit a brief timing chain rattle on cold start, associated with the variable valve timing system losing oil pressure after an extended cold soak. Early wear of the timing chain tensioner or guide rails amplifies this. While less catastrophic than the B47 diesel pattern, persistent rattle indicates tensioner wear requiring intervention before chain stretch causes misfires or timing deviation. Extended oil service intervals significantly accelerate wear.

The front of a dual overhead camshaft engine with the timing cover removed, exposing the timing chain and sprockets.Example of the part — not this vehicle

The front of a twin-cam engine with the timing cover off — chain, sprockets and guides.

Logansenf · CC BY-SA 4.0 · Wikimedia Commons

Symptoms to notice

  • Brief chain rattle on cold start, normally disappearing within a few seconds of oil pressure build-up
  • Rattle that persists longer than five seconds after start
  • Fault codes for cam timing deviation (P0011, P0014, P0016, P0017)
  • Rough idle until engine reaches operating temperature

What to check

Cold-start the engine and listen for chain rattle at the front of the engine. Note duration of any rattle. Review oil change intervals; extended intervals beyond manufacturer specification accelerate tensioner wear. If a workshop inspection is possible: Check for cam timing fault codes with a scan tool.

Where to look: Timing chain assembly at front of B58 engine, VANOS solenoids and chain tensioner

Parts involved: Timing chain.

Ask the seller

  • “Does the engine rattle briefly on first start of the day?”
  • “What oil change interval and specification has been used?”
  • “Have any cam timing fault codes appeared?”

05ZF 8HP torque converter clutch shudder

Drive at steady 60 to 90 km/h in light throttle and note any shudder through the floor or seat.petrol2013 onwardTransmission
OccasionalTransmission $500–$4,500 to fix

Can't confirm for this car

The ZF 8-speed automatic (8HP45 in 420i/428i, 8HP70 in 435i/440i) can develop torque converter clutch shudder, felt as a vibration at low speeds under light throttle application. Caused by wear of the converter clutch friction material or contaminated and degraded transmission fluid. ZF specifies Lifeguard 8 fluid; incorrect or aged fluid significantly accelerates wear. A fluid service resolves early cases; advanced wear requires torque converter replacement.

A cutaway automatic transmission torque converter showing the internal turbine and stator.Example of the part — not this vehicle

A torque converter, sectioned. The lock-up clutch inside is what shudders.

No machine-readable author provided. BerndB~commonswiki assumed (based on copyright claims). · CC BY-SA 3.0 · Wikimedia Commons

Symptoms to notice

  • Vibration or shudder felt through the drivetrain at 60 to 100 km/h under light throttle
  • Shudder disappears under hard acceleration or when throttle is released
  • Transmission fluid service may temporarily resolve or confirm the fault
  • Fault codes P0740 or P0741 (torque converter clutch slip)

What to check

  1. Drive at steady 60 to 90 km/h in light throttle and note any shudder through the floor or seat.
  2. Check transmission fluid condition and service history.
  3. A fluid change with correct ZF Lifeguard 8 fluid resolves early-stage shudder.
  4. Confirm fluid has been serviced within 60,000 km.

Where to look: ZF 8HP automatic transmission, internal torque converter clutch pack

Parts involved: Torque converter, Clutch.

Ask the seller

  • “Has the transmission fluid ever been changed, and with what specification fluid?”
  • “Have you noticed any shudder or vibration at highway speeds under light throttle?”
  • “Has the torque converter been replaced or inspected?”

068HP70/8HP90 solenoid valve body wear

Check transmission fluid condition and service history.petrol2020 onwardTransmission
OccasionalTransmission $1,500–$4,000 to fix

Can't confirm for this car

The G22/G26 4 Series with the 8HP70 or 8HP90 automatic transmissions can develop solenoid valve wear, causing erratic gear changes, delayed engagement from rest, or the transmission entering limp-home mode. Solenoid valve bodies are a known wear item in ZF 8-speed units when transmission fluid is neglected or incorrect fluid type is used. The G22 generation uses a sealed-for-life specification that BMW recommends never changing, but fluid degradation at higher mileages causes solenoid stiction.

Symptoms to notice

  • Harsh or hesitant gear changes, particularly the 1-2 upshift
  • Delayed or clunky engagement when selecting Drive from Park or Neutral
  • Transmission warning light or limp-home mode activation
  • Fault codes P0748, P0778 or solenoid electrical/pressure faults

What to check

  1. Check transmission fluid condition and service history.
  2. Drive from cold and note the quality of gear changes.
  3. Scan for transmission fault codes.
  4. Verify correct fluid type has been used; incorrect fluid accelerates solenoid wear significantly.

Where to look: ZF 8HP transmission valve body, internal solenoid pack

Parts involved: Mechatronic / valve body.

Ask the seller

  • “Has the transmission fluid ever been serviced despite being listed as sealed-for-life?”
  • “Have you noticed any harsh or delayed gear changes?”
  • “Has a transmission warning light appeared?”

07B58 valve cover PCV diaphragm failure and valve cover gasket leak (440i)

With the engine idling, listen at the top of the engine for a whistle or squeal that is not the belt.petrol2016–2020Engine
CommonEngine $300–$2,500 to fix

Can't confirm for this car

The first-generation B58 (B58A) builds its crankcase ventilation (PCV) valve into the plastic valve cover, using a spring-loaded rubber diaphragm to control crankcase pressure. The diaphragm wears or tears, which lets oily vapour into the intake and can cause whistling, rough idle, smoke and higher oil use; separately the valve cover gasket hardens and seeps oil. BMW sells a diaphragm repair kit for the B58A, but many cars end up with a whole new valve cover. Owner reports on Bimmerpost include a 340i needing a valve cover and oil separator for a smoking exhaust.

Symptoms to notice

  • Whistle or squeal from the engine at idle
  • Rough idle or misfire
  • Blue or white smoke from the exhaust, worst on start-up
  • Oil seeping around the valve cover or burning oil smell
  • Oil level dropping between services

What to check

With the engine idling, listen at the top of the engine for a whistle or squeal that is not the belt. With the engine off, look under the oil filler cap for a creamy white or yellow residue, and note if the cap is very hard to lift off with the engine running because of suction. Use a phone torch along the edges of the valve cover for oily wetness or dust caked on oil. Watch the exhaust on start-up and after the test drive for blue or white smoke. Ask how much oil the car uses between services and whether the valve cover or PCV has been replaced. If a workshop inspection is possible: have the fuel trims and misfire counters read and crankcase pressure checked.

Where to look: Top of the engine: plastic valve cover with the integrated PCV valve

Parts involved: Rocker / valve cover, PCV / oil separator.

Ask the seller

  • “Has the valve cover or PCV valve been replaced?”
  • “How much oil does it use between services?”
  • “Does it ever smoke or whistle at idle?”

08N55 high-pressure fuel pump (HPFP) failure

Observe cold-start behaviour on first crank.petrol2013–2016EngineRead the full fault: symptoms, where to look, what to ask the seller

09B58 coolant loss from plastic hoses, expansion tank and thermostat seals (440i)

With the engine cold, check the coolant expansion tank level against the marks and look at the tank and its cap for cracks or dried residue.petrol2016–2020Cooling
CommonCooling $250–$1,800 to fix

Can't confirm for this car

The first-generation B58 in the 440i relies on a lot of plastic in its cooling system: the expansion tank and cap, the vent hoses to the tank, the quick-connect hose joints and the O-ring seal on the thermostat (heat management) module. As the plastic ages and the seals harden, owners report slow coolant loss and low coolant warnings, often with no obvious puddle because the leak evaporates on the hot engine. Specialist workshops single out the plastic hose connector behind the heat management module as a frequent culprit. Caught early it is a hose, seal or tank; ignored, the engine can overheat.

An annotated photograph of an automotive engine thermostat identifying the wax capsule and both disc valves.Example of the part — not this vehicle

A double-valve engine thermostat, labelled: the wax capsule is what sticks.

Dougsim · CC BY-SA 3.0 · Wikimedia Commons

Symptoms to notice

  • Low coolant warning on the dash
  • Sweet coolant smell after driving
  • White or pink crusty residue around hose joints or the expansion tank
  • Temperature reading or heater behaving erratically

What to check

With the engine cold, check the coolant expansion tank level against the marks and look at the tank and its cap for cracks or dried residue. Use a phone torch to follow the plastic hoses and quick-connect joints around the top and front of the engine and the thermostat housing for white or pink crust, which is dried coolant. Smell for sweet coolant after the test drive and watch the temperature reading stay steady in traffic. Ask how often the car needs coolant topped up and whether any cooling parts have been replaced. If a workshop inspection is possible: have the cooling system pressure-tested cold and hot, which finds seeps that only open up when warm.

Where to look: Top and front of the engine bay: coolant expansion tank, thermostat (heat management) module and plastic coolant hoses

Parts involved: Coolant expansion tank, Thermostat.

Ask the seller

  • “How often do you top up the coolant?”
  • “Has the expansion tank, thermostat or any coolant hose been replaced?”
  • “Has the car ever overheated or shown a coolant warning?”

10N55 3.0T plastic charge pipe splitting under boost (435i)

This fault will not show on a gentle drive, so take the car onto an open road and use full throttle in third gear at least twice, up to legal speed.petrol2013–2018EngineRead the full fault: symptoms, where to look, what to ask the seller

11B48 cylinder head coolant vent line coupling breaks, sudden coolant loss (SIB 17 01 21, 420i/430i)

With the engine cold, check the coolant expansion tank level against the marks.petrol2016–2019Cooling
CommonCooling $200–$600 to fix

Can't confirm for this car

On the four-cylinder B46/B48 turbo engine in the F32/F33/F36 420i/430i, a thin plastic coolant vent line runs from the cylinder head to the expansion tank. BMW found that its quick-disconnect coupling cannot cope with engine heat over the life of the part and can snap off at the cylinder head, dumping coolant and risking overheating if the car is driven on. BMW issued service action SIB 17 01 21 (revised April 2022) to replace the line on F22, F23, F30, F31, F32, F33, F34 and F36 cars built from 24 April 2015 to 24 September 2019. That bulletin is a BMW North America document, so a NZ or AU car may never have had the new line fitted; the part itself is cheap, the risk is overheating damage if the coupling lets go on the road.

A removed six-cylinder diesel engine cylinder head on cardboard, valve-gear side facing up.Example of the part — not this vehicle

A six-cylinder diesel head off the engine, valve-gear side up. Cracks run between the valve seats on the face beneath.

Ll1324 · CC0 · Wikimedia Commons

Symptoms to notice

  • Low coolant warning, sometimes suddenly
  • Coolant smell or steam from the engine bay
  • Coolant residue around the top of the engine near the expansion tank
  • Temperature warning or reduced power

What to check

With the engine cold, check the coolant expansion tank level against the marks. Use a phone torch to follow the thin plastic hose running from the top of the cylinder head to the expansion tank and look at its joint on the engine for cracks, weeping or white or pink crusty residue. Smell for coolant after the test drive and watch the temperature reading. Ask whether the cylinder head coolant vent line has been replaced, and ask a BMW dealer to check the VIN for open service actions including SIB 17 01 21. If a workshop inspection is possible: have the cooling system pressure-tested and the vent line coupling inspected at the cylinder head.

Where to look: Top of the engine: plastic coolant vent line between the cylinder head and the coolant expansion tank

Parts involved: Cylinder head.

Ask the seller

  • “Has the cylinder head coolant vent line been replaced under BMW service action SIB 17 01 21?”
  • “Has the car ever shown a low coolant warning or overheated?”
  • “How often do you top up the coolant?”

12B58 plastic charge pipe crack or coupler blow-off, sudden boost loss (440i)

On the test drive, accelerate firmly from low revs in a safe place and listen for a hiss or whoosh and feel for power suddenly falling away.petrol2016–2020Engine
OccasionalEngine $450–$1,100 to fix

Can't confirm for this car

The first-generation B58 feeds boosted air from the turbo to the throttle through an all-plastic factory charge pipe. With age and heat the plastic and its coupler become brittle, and the pipe can crack or pop off under boost, giving a sudden loud whoosh, a big loss of power and limp mode. It is far less common than on the older N55, but the risk climbs steeply on tuned cars running extra boost, and the 440i is a very commonly tuned car. Many owners fit an aluminium aftermarket pipe; on its own that is a sign of modification worth asking about.

Symptoms to notice

  • Sudden loss of power under hard acceleration
  • Loud hiss, whoosh or pop under boost
  • Engine warning light and limp mode
  • Car feels flat until restarted

What to check

On the test drive, accelerate firmly from low revs in a safe place and listen for a hiss or whoosh and feel for power suddenly falling away. Watch the dash for an engine warning or drivetrain malfunction message. With the bonnet up, look at the large pipe running across the front of the engine to the throttle for cracks, oily residue at the joints or a non-standard aluminium pipe. Ask whether the car has been tuned or remapped, and whether the charge pipe has ever split. If a workshop inspection is possible: have a boost leak (smoke) test done and stored boost deviation codes read.

Where to look: Front of the engine: plastic charge pipe between the intercooler outlet and the throttle body

Parts involved: Turbocharger.

Ask the seller

  • “Has the car been tuned, remapped or fitted with a piggyback?”
  • “Has the charge pipe ever cracked or been replaced?”
  • “Has it ever gone into limp mode?”
Electrical1

01B46/B48 starter motor premature wear — overheat and fire recall 26V-056 / 26V-438 (430i)

An internal component in the starter motor fitted to the 2.0-litre four-cylinder cars wears early.petrol2022–2025Electrical
OccasionalElectrical $0–$1,500 to fix

Can't confirm for this car

An internal component in the starter motor fitted to the 2.0-litre four-cylinder cars wears early. In mild cases the car simply refuses to start; in the worst cases the starter draws enough current to overheat and catch fire. BMW recalled it in the United States as campaign 26V-056 in early 2026 and expanded it to 26V-438 in July 2026, covering the 4 Series Coupe and Convertible built from September 2022 and the Gran Coupe built from October 2022, all 430i and 430i xDrive. The remedy is a starter of a different design fitted free of charge. New Zealand and Australian cars come off the same lines, so a 430i from this window needs its VIN checked against the recall register before purchase.

Symptoms to notice

  • Slow, laboured or repeated cranking before the engine catches
  • Clicking with no crank, intermittently
  • Hot electrical or burning smell from the engine bay after trying to start
  • No-start that clears once the car has sat for a while

What to check

Arrive while the car is stone cold and make the very first start of the day yourself — the engine should catch within about a second, with no grinding, slow spin or hesitation. Start and stop the car three or four times during the viewing, including once when it is fully hot, and listen each time. Sniff around the engine bay after a hot restart for any hot electrical smell. Ask the seller whether the starter recall has been carried out and for the paperwork, then have a BMW dealer check the VIN against open recalls, which costs nothing. If the car has an aftermarket alarm or immobiliser wired into the start circuit, treat any cranking hesitation as unexplained until it has been looked at properly.

Where to look: Starter motor low on the gearbox bellhousing at the back of the engine, on the right-hand side.

Parts involved: Starter motor.

Ask the seller

  • “Has the starter motor recall been carried out on this VIN?”
  • “Has the car ever failed to start or been slow to crank?”
  • “Has the starter motor ever been replaced?”
Body, brakes, suspension & interior3

01Takata driver airbag inflator recall PRA 2018/17191 (F32/F33/F36 4 Series, 2013-2017)

Some 2013 to 2017 F32/F33/F36 4 Series cars (all engines) were built with a Takata driver's airbag whose propellant can absorb moisture over time.2013–2017Interior
OccasionalInterior $0–$1,500 to fix

Can't confirm for this car

Some 2013 to 2017 F32/F33/F36 4 Series cars (all engines) were built with a Takata driver's airbag whose propellant can absorb moisture over time. In a crash the inflator can over-pressurise and rupture, throwing metal fragments at the driver, which can cause serious injury or death. BMW Australia recalled F Series cars in a staged campaign from December 2018 (PRA 2018/17191) to replace the airbag free of charge, and a separate 2024 recall (REC-006035) covers cars later fitted with a steering wheel that has a Takata inflator. Have the VIN checked to confirm the recall work is done. Not every car is in the recall; a dealer check of the VIN is the only way to know.

Symptoms to notice

  • No visible symptom: the defect only shows when the airbag deploys
  • Airbag warning light on the dash may indicate an airbag module has been disturbed or replaced with a non-genuine part

What to check

  1. Ask the seller for the BMW dealer invoice showing the Takata driver airbag recall (PRA 2018/17191) was done, and ring a BMW dealer with the VIN to confirm there are no open airbag recalls.
  2. Check the airbag warning light comes on at start-up and goes out after a few seconds.
  3. Look at the steering wheel: if it has been swapped for a different style, ask where it came from, because swapped wheels are covered by a separate Takata recall (REC-006035).
  4. If a workshop inspection is possible: have a BMW dealer read the vehicle recall history by VIN and check the airbag module part label against the recall list.

Where to look: Driver airbag in the centre of the steering wheel

Ask the seller

  • “Has the Takata driver airbag recall been done, and do you have the dealer invoice?”
  • “Has the steering wheel ever been replaced or swapped for a different style?”
  • “Has the airbag warning light ever come on?”

02F33 Convertible retractable hardtop hydraulic and microswitch failure

2014–2020Body & RustRead the full fault: symptoms, where to look, what to ask the seller

03F32/F36 4 Series power steering motor bolt corrosion, sudden loss of steering assist (2013-2015 builds)

With the engine running and the car stopped, turn the steering wheel lock to lock: it should be light and smooth with no clunks or notchy spots.2013–2015Suspension
OccasionalSuspension $300–$4,500 to fix

Can't confirm for this car

On F32 and F36 4 Series built from mid 2013 to May 2015, the bolts holding the electric power steering motor to the steering rack can rust and snap. When that happens the car loses steering assist, so the wheel suddenly becomes very heavy, mostly at parking speeds, and there may be a clunk from the front when turning. BMW recalled these cars in Canada (recall 2021093) and extended the warranty in the US (bulletin SIB 01 26 18) to replace the bolts, or the whole steering rack if a bolt has already broken. We found no NZ or AU recall, so check the car's history.

Symptoms to notice

  • Steering suddenly heavy, especially when parking
  • Steering fault warning on the dash
  • Clunk or knock from the front when turning the wheel

What to check

With the engine running and the car stopped, turn the steering wheel lock to lock: it should be light and smooth with no clunks or notchy spots. On the test drive, check for any steering warning on the dash and that the assist does not come and go. Ask whether the steering rack or its motor bolts have ever been replaced. If a workshop inspection is possible: lift the car and look at the steering motor on the rack for rusted, loose or missing mounting bolts.

Where to look: Electric motor on the front steering rack, low down behind the front axle

Parts involved: Steering rack, Body corrosion.

Ask the seller

  • “Has the steering ever gone heavy or shown a warning?”
  • “Has the steering rack or its motor bolts been replaced, and do you have the invoice?”
Fluid leaks4

01B58 oil filter housing gasket leak, oil and coolant (440i)

The first-generation B58 3.0 turbo six in the F32/F33/F36 440i has a plastic oil filter housing that also carries the oil-to-coolant heat exchanger.petrol2016–2020Fluid Leaks
CommonFluid Leaks $700–$2,200 to fix

Can't confirm for this car

The first-generation B58 3.0 turbo six in the F32/F33/F36 440i has a plastic oil filter housing that also carries the oil-to-coolant heat exchanger. With heat cycling the gaskets between the housing, the block and the cooler flatten, and the plastic can warp or crack, so the engine weeps oil, coolant or both. Oil runs down the intake side of the engine and a coolant leak into the oil can mix the two fluids, which is the expensive outcome. BMW faces a US class action over this housing on B46, B48 and B58 engines in 2014 to 2021 1, 2, 3 and 4 Series cars; there is no recall or extended warranty in NZ or AU.

Symptoms to notice

  • Burning oil smell after a drive
  • Oil wetness on the left (intake) side of the engine below the filter housing
  • Coolant level slowly dropping with no puddle
  • Milky or oily film in the coolant expansion tank

What to check

With the bonnet up and the engine cold, use a phone torch to look down the intake side of the engine around the oil filter housing and below it for wet oil, crusty white or pink coolant residue, or signs of fresh cleaning. Check the coolant expansion tank level and look for an oily film on the coolant. Look under the oil filler cap for a milky, mayonnaise-like layer. After the test drive, sniff for a hot oil smell at the bonnet shut line. Ask whether the oil filter housing or its gaskets have been replaced and ask for the invoice. If a workshop inspection is possible: have the cooling system pressure-tested and the housing area checked from underneath on a hoist for oil and coolant tracking.

Where to look: Left (intake) side of the engine at the front, where the oil filter canister screws in from the top

Parts involved: Turbocharger.

Ask the seller

  • “Has the oil filter housing or its gaskets ever been replaced?”
  • “Do you have to top up coolant between services?”
  • “Has the car ever shown a low coolant warning?”

02B48 oil cooler gasket leak

Remove engine undertray and inspect oil cooler housing on the right-hand side of the block for oil staining.petrol2016 onwardFluid LeaksRead the full fault: symptoms, where to look, what to ask the seller

03N20 2.0T oil filter housing gasket leak (420i/428i)

petrol2013–2016Fluid Leaks
CommonFluid Leaks $450–$1,100 to fix

Can't confirm for this car

The 2.0 litre N20 turbo four-cylinder in the F32/F33/F36 4 Series 420i and 428i seals its plastic oil filter housing (which also carries the oil cooler connections) to the block with rubber gaskets that harden and shrink with heat over the years. Once they shrink, oil seeps down the side of the engine and the leak gets steadily worse; specialists rate it one of the most common oil leaks on this engine. Left alone it drops the oil level and soaks surrounding parts in oil, and the repair means removing the engine computer and part of the intake to reach the housing bolts. There is no recall or extended warranty for this leak.

Symptoms to notice

  • Burning oil smell after a drive
  • Oily film or caked grime on the side of the engine below the oil filter cap
  • Oil drips under the front of the car
  • Oil level dropping between services

What to check

  1. With the bonnet up and a phone torch, look down the side of the engine below the oil filter housing (the black cap on top of the oil filter) for wet, dark oil or caked grime.
  2. Check the ground under the front of the car where it has been parked.
  3. Smell for burning oil after the test drive.
  4. Ask whether the oil filter housing gasket has been replaced and for the invoice.
  5. If a workshop inspection is possible: put the car on a hoist and check the underside of the engine and the undertray for oil tracking down from the housing.

Where to look: Engine bay, the oil filter housing on the side of the engine block under the intake

Parts involved: Turbocharger.

Ask the seller

  • “Has the oil filter housing gasket been replaced, and do you have the invoice?”
  • “Does it need topping up with oil between services?”
  • “Has a workshop ever mentioned an oil leak?”

04M Sport rear differential breather and cover leak (G22/G23/G26 430i xDrive and M440i)

2020 onwardFluid Leaks
OccasionalFluid Leaks $650–$1,400 to fix

Can't confirm for this car

Early cars of this generation — most often M440i and xDrive models with the M Sport torque-vectoring differential — left the factory overfilled, and oil is pushed out through the breather on top of the differential housing under hard acceleration, worst when the diff is still cold. The result is oil down the back of the differential and sometimes onto the exhaust. BMW's answer was a revised differential cover with a modified breather tube, fitted under warranty. On its own it is a mess rather than a mechanical failure, but a car that has been weeping for years with nobody checking the level can end up genuinely low, and a rear differential that runs dry whines and then seizes.

Symptoms to notice

  • Oily film or drips on the rear differential housing and the underbody behind it
  • Faint hot-oil smell after a spirited drive
  • Small dark spots on the driveway under the rear of the car
  • Whine or drone from the rear axle at a steady cruise on a car that has run low

What to check

  1. Crouch behind a rear wheel and shine your phone torch up at the differential between the rear wheels, looking for a wet or grimy film on the top and back of the casing.
  2. Look at the ground where the car normally parks for small dark spots under the rear axle.
  3. On the test drive accelerate hard from about 60 km/h once the car is warm, then look at the same area again and sniff for hot oil.
  4. Ask whether the differential cover has been replaced under warranty with the revised part, and whether the oil level has been checked since.
  5. Listen on a quiet road at a steady 80 to 100 km/h for any whine from behind you that rises and falls with road speed.

Where to look: Rear differential between the rear wheels on the underside of the car — the breather sits on top of the housing with a short hose, and the cover is the finned plate at the rear face.

Parts involved: Differential.

Ask the seller

  • “Has the rear differential cover been replaced under warranty with the revised part?”
  • “Has the differential oil level ever been checked or topped up?”
  • “Is there any whine from the rear axle at a steady cruise?”

BMW 4 Series faults in detail

Each of these has its own page: the symptoms, where to look, what to ask the seller and what the repair costs. Free, no account needed.

B48 oil cooler gasket leakMajor · Fluid LeaksElectric coolant pump seizure — overheating with no warning (N20/N55 420i/428i/435i)Critical · CoolingF33 Convertible retractable hardtop hydraulic and microswitch failureMajor · Body & RustN20 2.0T timing chain guide and tensioner failure (420i/428i)Critical · EngineN55 3.0T plastic charge pipe splitting under boost (435i)Major · EngineN55 high-pressure fuel pump (HPFP) failureMajor · Engine

What these repairs cost on other cars

Some of the BMW 4 Series’s documented faults are repairs other models share. Each page lists the documented NZ cost for every model it affects.

Other BMW models

BMW 3 Series88 documented faultsBMW 5 Series58 documented faultsBMW 1 Series50 documented faultsBMW M314 documented faultsBMW 7 Series12 documented faultsBMW X411 documented faults

BMW 4 Series buyer questions

Is the BMW 4 Series reliable?

Like any used car, it depends on the specific example and its service history. Across the 20 documented faults for the BMW 4 Series, the recurring problem areas are engine, cooling, and electrical. A BMW 4 Series with a full service history and no signs of the issues listed on this page can be a sound buy but each one needs to be checked individually before you commit.

What are the most common problems with a used BMW 4 Series?

We've catalogued 20 known faults for the BMW 4 Series, covering engine, cooling, and electrical. All 20 are written out in full on this page, with the symptoms to notice, what to inspect, and typical repair costs for each. Free to read, no account needed.

How much do repairs cost on a BMW 4 Series?

Most single repairs on the BMW 4 Series fall between $500–$2,200 at NZ independent-workshop rates. Some of the 20 documented faults cost less and a few cost considerably more, and no one car needs them all. Knowing which ones to look for before you view is what lets you negotiate the price down or walk away.

Should I get a pre-purchase inspection on a BMW 4 Series?

Yes. A BMW 4 Series inspection focused on its known weak points is the single best way to avoid an expensive mistake. KickTyres gives you a guided, model-specific inspection plus a market valuation and negotiation figure for $24.90 far less than the cost of missing one of the faults on this page.