The G22 is BMW's second-generation 4 Series coupe, sharing its CLAR platform and B48 powertrain with the G20 3 Series. The 420i offers 184 hp from a proven 2.0-litre turbo four that has been in production since 2014, paired exclusively with the reliable ZF 8-speed automatic. From 2021, a 48V mild-hybrid system was added for improved fuel economy and smoother stop-start behaviour.· more· less
Proven B48 engine, no timing chain issuesReliable ZF 8-speed automatic
Oil filter housing prone to crackingStarter motor fire recall on all models
Buy if: You want a refined premium coupe with a well-understood engine and can verify the starter motor recall has been completed.
Avoid if: You need minimal maintenance complexity or cannot budget for BMW-typical gasket and cooling system repairs.
Polycarbonate oil filter housing cracks or gasket fails, leaking oil and potentially contaminating coolant · more· less
This is the most well-documented B48 engine issue and is the subject of a 2026 class action lawsuit in the US covering B46, B48, and B58 engines. The oil filter housing is made of polycarbonate plastic and sits between the engine block and intake manifold. Repeated thermal cycling causes the housing to become brittle and crack, while the gasket between the housing and engine block hardens and shrinks over time. Failure typically occurs between 60,000 and 120,000 km. Early symptoms include minor oil seepage visible from below, oil smell on the engine, or in more serious cases, coolant mixing with oil (milky residue on the oil cap). If coolant enters the oil circuit, engine damage can follow quickly. Repair requires removing the intake manifold for access. Independent BMW specialists in Western Europe typically charge €400-700 for gasket replacement or €600-1,200 if the entire housing needs replacing. BMW dealers charge more, with quotes reaching €1,000-1,500. Upgraded aluminium aftermarket housings are available and recommended for cars that have already experienced this failure once.
Starter motor fire risk (global recall)
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Wear in starter magnetic switch can cause short circuit, overheating, and vehicle fire even while parked · more· less
BMW announced a global recall in late 2025 and early 2026 affecting approximately 575,000 vehicles worldwide, including all G22 4 Series models. A manufacturing defect in the starter motor's magnetic switch allows metal particles to accumulate from normal start cycles, eventually causing a short circuit. This can generate intense heat in the starter assembly, with the potential to ignite surrounding components and cause a vehicle fire, even when the car is parked and the engine is off. BMW and safety regulators have urged owners to park affected vehicles outdoors, away from structures, until the repair is completed. The recall remedy involves replacing the starter motor and in some cases the battery, entirely free of charge. On a used car, this is the single most important item to verify before purchase. Contact BMW with the VIN to confirm the recall has been completed. If the car is outside warranty and the recall somehow does not apply, a starter motor replacement costs approximately €400-500 at an independent specialist.
Coolant vent line cracking
€200 - 8003 of 8
Rigid plastic coolant tube between cylinder head and expansion tank becomes brittle and cracks from heat cycling · more· less
The B48 engine uses a small rigid plastic coolant vent line that runs from the top of the cylinder head to the coolant expansion tank, positioned very close to the turbocharger. The proximity to turbo heat causes this plastic tube to become increasingly brittle over time and mileage. BMW issued a Technical Service Bulletin (SIB 17 01 21) in February 2022 acknowledging this issue and offering a revised rubber replacement part. In some markets, this was covered as a free service action. The tube can crack gradually, causing slow coolant loss that may not trigger an immediate warning, or snap completely, leading to rapid coolant loss and potential overheating. Symptoms include slowly declining coolant level, white residue around the tube fittings, or a sudden coolant warning. The replacement part itself is inexpensive (under €50), but labour at a BMW dealer can push the total to €400-800 due to access complexity. Independent shops typically handle this for €200-400. Check whether the revised rubber part has already been fitted, as this is considered a one-time fix.
Valve cover gasket leak
€350 - 8004 of 8
Valve cover gasket hardens from thermal cycling and begins leaking oil onto the engine block · more· less
The B48 valve cover uses an integrated PCV (positive crankcase ventilation) system, which means the entire valve cover assembly is affected when the gasket fails. The gasket hardens and shrinks from repeated heat cycles, typically starting to seep oil around 80,000-120,000 km. Oil drips onto the engine and exhaust components, producing a burning oil smell that is often the first symptom noticed by owners. The valve cover gasket itself is an inexpensive part (approximately €30-50), but the repair is labour-intensive because the ignition coils, fuel injectors, and several electrical connectors must be disconnected, and many technicians remove the intake manifold for better access. BMW dealers typically charge €600-800 for this repair. Independent specialists charge €350-500. Many owners combine this repair with the oil filter housing gasket, as the two jobs share overlapping labour. If deferred too long, oil can damage the serpentine belt and other rubber components below.
Electric water pump failure
€500 - 1,2005 of 8
Electric coolant pump fails, causing overheating or reduced cabin heating, typically after 100,000 km · more· less
The B48 uses an electric water pump that has been improved over earlier BMW designs but remains a known wear item. The pump is electronically controlled and can fail electrically (motor burnout) or mechanically (impeller degradation). Failure typically occurs between 100,000 and 150,000 km, though some owners report earlier issues. Symptoms include coolant temperature warnings, erratic temperature gauge behaviour, reduced cabin heating, or in worst cases, engine overheating. The part costs approximately €300-400, with several hours of labour required due to packaging constraints. Most specialists recommend replacing the thermostat at the same time, as the integrated electronic thermostat is another common failure point at similar mileage. Total repair cost including both components runs €500-800 at independent shops and €800-1,200 at BMW dealers.
iDrive 8 infotainment glitches
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Random reboots, blank screens, Bluetooth dropouts, and Apple CarPlay disconnections on 2021+ models · more· less
Cars equipped with iDrive 8 (standard on G22 models from mid-2021 onwards) have experienced a range of software-related problems. Forum reports from Bimmerpost and BimmerFest document random screen reboots during driving, the central display going blank for 30-60 seconds before recovering, Bluetooth pairing failures after phone software updates, and Apple CarPlay or Android Auto connections dropping intermittently. The navigation screen occasionally loses traffic data while the instrument cluster continues to function normally. Most of these issues have been addressed through over-the-air software updates, and BMW dealers can apply the latest software version free of charge during warranty. Out of warranty, a dealer diagnostic session and software update costs approximately €150-300. While these glitches are annoying rather than dangerous, they are widely reported and affect day-to-day usability. Earlier G22 models (2020-mid 2021) with iDrive 7 are generally less affected by these software stability issues.
Folding mirror electronics failure
€300 - 7007 of 8
Moisture ingress or motor seizure causes power-folding mirrors to stop working · more· less
A commonly reported issue on G-platform BMWs including the G22. The folding mirror mechanism can fail due to moisture entering the mirror electronics module, causing a short circuit on the wiring. This often occurs after cold weather, car washes, or when the mirror encounters resistance from ice. The folding motor itself can also seize or burn out. Symptoms include one or both mirrors failing to fold or unfold on command, grinding noises from the mirror housing, or intermittent operation. The Footwell Module (FRM) detects an over-current fault when motor stiction increases. Replacement of a single mirror assembly with auto-dim and folding function costs approximately €400-700 at a BMW dealer, or €300-500 at an independent specialist. The module typically needs coding after replacement. Some owners report recurring failures, particularly in wet climates.
12V AGM battery degradation
€250 - 5008 of 8
High electrical load from 48V system and driver assistance features accelerates 12V battery wear · more· less
The G22 420i has a heavy electrical load from its iDrive system, driver assistance features, and the 48V mild-hybrid integration (on 2021+ models). The 12V AGM battery manages the vehicle's conventional electrical systems and is under significant stress, particularly on cars that make frequent short trips or sit unused for extended periods. Battery degradation is commonly reported between 4 and 6 years of age, or around 50,000-80,000 km. Unlike older BMWs where a simple swap was sufficient, the G22 requires the new battery to be registered and coded to the vehicle's intelligent charging system through BMW diagnostic software. Without this step, the charging algorithm will remain calibrated to the old battery, accelerating failure of the replacement. Independent BMW specialists charge €250-350 for supply and coding, while BMW dealers charge €400-500. A quality battery tender (such as CTEK MXS 5.0) is strongly recommended if the car is parked for more than a week at a time.
Proven B48 powertrain with typical BMW gasket and electronics concerns
The B48 engine in the G22 420i has established itself as one of BMW's more reliable modern petrol units, with no timing chain weakness and a robust bottom end. The main ownership costs centre on the well-documented oil filter housing and valve cover gasket leaks, which are predictable in both timing and cost. The global starter motor recall is the most critical safety item to verify on any used example. The 48V mild-hybrid system has been largely trouble-free, and the ZF 8-speed automatic is proven across millions of applications. Budget for gasket-related repairs in the €80,000-120,000 km range and this is a dependable long-distance coupe.
Service history
Complete BMW dealer or specialist records essential. Verify oil changes every 12 months or 15,000 km maximum. The B48 benefits from shorter oil change intervals.
Tires
Check tread depth, age (DOT date codes), and uneven wear patterns. Run-flat tires are standard and more expensive to replace.
Cold start
Must start engine completely cold. Listen for unusual sounds during the first few seconds. Brief VANOS rattle on startup is not uncommon but should disappear within 1-2 seconds.
Test drive
Minimum 30 minutes including highway driving and city stop-start to evaluate gearbox behaviour, infotainment stability, and mild-hybrid system integration.
Specific for this vehicle
Verify starter motor recall completed
Contact BMW with the VIN to confirm. This is the most important pre-purchase check on any G22. Do not purchase without verification.
Inspect engine underside for oil seepage
Look around the oil filter housing area and valve cover edges for signs of oil. Dark wet stains on the engine block or components below indicate active leaks.
Check coolant level and expansion tank condition
Low coolant or white residue around hose connections suggests coolant vent line or oil filter housing cross-contamination. Check oil cap for milky residue.
+ 4 more checksShow less
Test both folding mirrors
Fold and unfold mirrors multiple times using the switch. Listen for grinding noises or observe any hesitation. Check for moisture behind mirror glass.
Test iDrive 8 thoroughly (2021+ models)
Pair phone via Bluetooth, test Apple CarPlay/Android Auto, navigate through menus. Drive for at least 15 minutes to check for reboots or screen blanking.
Check 12V battery health reading
Ask the seller or dealer to show the battery health status via BMW diagnostics. Ask when the battery was last replaced and whether it was coded to the car.
Inspect coolant vent line (above cylinder head)
If accessible, check whether the original rigid plastic line has been replaced with the revised flexible rubber part. White residue or brittleness indicates replacement is needed.
Recalls and Technical Service Bulletins
Starter motor fire risk (2020-2024, global recall affecting 575,000 BMW vehicles)Critical - verify completed
Coolant vent line cracking (TSB SIB 17 01 21, service action for revised rubber replacement)Verify completed
Door locking ECU programming error (2023 430i/M440i Gran Coupe and Coupe models)Verify if applicable
Contact BMW with the VIN to verify all recalls and service actions have been completed. The starter motor recall is a fire safety issue and the single most critical item to verify before purchase. BMW can also confirm whether the coolant vent line service action has been performed.
Warranty Status
Factory warranty (2 years, no km limit)Expired on 2020-2023 models. 2024+ models may still have coverage.
Extended warranty (BMW Premium Selection)Available through BMW dealers, typically 1-2 additional years.
Rust perforation warranty12 years from first registration.
BMW offers a 2-year factory warranty with no kilometre limit (3 years on cars ordered from November 2016 under the 2+1 programme, subject to conditions). All G22 models built before 2024 are outside the standard warranty period. BMW Premium Selection and third-party extended warranties are available.
Sources: Research draws on model-specific owner forums and owner communities, recall information from official authorities, German automotive press, and multiple workshop cost references cross-checked against each other.
This report is for informational purposes only and does not constitute professional advice. Estimates may be inaccurate. Always have a qualified specialist inspect the vehicle before purchase. We accept no liability for decisions made based on this information.
