The M550i bridges the gap between standard 5 Series and M5, offering serious performance for less money. The N63TU2 engine in the G30 M550i is significantly improved over early N63 variants (2008-2013) which had catastrophic reliability issues. Key concerns: turbo coolant lines leak onto alternator (60,000-100,000 km), wastegate actuators fail causing limp mode, valve stem seals degrade from hot-V design heat, and timing chain tensioners can rattle on cold start. Transmission is solid ZF 8-speed. Electrical system is complex and prone to battery drain issues. Not cheap to maintain, but far more reliable than early N63 engines.
The turbos sit in the valley of the V8, creating extreme heat that degrades coolant line rubber. Lines pass directly above the alternator. When they leak, coolant drips onto alternator causing electrical burning smell and alternator failure. Symptoms include coolant smell in cabin, low coolant warnings, and visible smoke. Typically occurs 60,000-100,000 km. BMW had a customer care campaign for some vehicles. Dealer quotes €2,300-6,000 depending on additional damage. Independent shops €1,500-2,100. Stainless steel upgrade lines available.
Valve stem seals fail€4,000 - €10,000
Hot-V turbo heat accelerates seal degradation, causes oil consumption and blue smoke · more· less
The N63's hot-V design (turbos in valley) creates extreme heat that degrades valve stem seals prematurely. Symptoms: adding 1 quart oil every 300-500 miles, blue smoke from exhaust after idling. All 32 valve seals require replacement. Engine must be dropped or extensively disassembled. Dealer quotes €9,000-10,000+. BMW specialists €4,000-5,900. Index 12 injectors recommended during this repair. N63TU2 in G30 less prone than early N63, but still affected by design.
Timing chain tensioner rattle€2,500 - €5,000
Tensioner loses pressure overnight, causes cold start rattle for 1-30 seconds · more· less
N63 timing chain tensioner has release valve that weakens over time, allowing oil pressure to bleed overnight. Results in distinctive rattle on cold start lasting 1-30 seconds. Much less common on N63TU2 (G30 M550i) than early N63, but still occurs. If rattle persists beyond few seconds, chain stretch is likely - catastrophic if ignored (valve/piston contact). Repair includes chain, guides, tensioners, sprockets. Early N63 (2008-2013) had widespread failures; BMW issued customer care package. G30 M550i uses improved TU2 version with better reliability.
Turbo wastegate actuator failure€1,500 - €4,200
Wastegate sticks causing limp mode, drivetrain malfunction warning · more· less
Common fault codes P2ABA, P12C4, P12C6 indicate wastegate sensor/actuator issues. Symptoms: drivetrain malfunction light, limp mode, reduced power, rattling at certain RPM. Can occur as early as 28,000 km. Single actuator replacement €1,500 at dealer. Since M550i has twin turbos, both may eventually need replacement. Full turbo assembly €3,600-4,200. Labor approximately 1.8 hours (18 FRUs). Wastegate failures can lead to overboost/underboost conditions causing engine damage if ignored.
Fuel injector failure€3,500 - €8,000
Early N63 injectors fail frequently; Index 12 much improved but still vulnerable · more· less
N63 fuel injectors have been redesigned multiple times. Early versions failed frequently (some owners report replacement every 20-30k miles). Symptoms: rough idle, poor fuel economy, misfires. G30 M550i uses improved Index 12 injectors which are more reliable. Single injector €450, full set of 8 €3,500-4,600. Labor approximately 11 hours for full set, 4 hours for single. When one fails, others on same bank likely to follow - replace bank or full set. Low-grade fuel accelerates failure. N63TU2 significantly better than early N63.
M550i known for battery drain when parked. Causes: faulty Intelligent Battery Sensor (IBS) on negative terminal, key fob too close activating comfort access, faulty control modules, aftermarket devices. Symptoms: dead battery after days parked, intermittent iDrive/parking sensors, warning lights. Battery must be registered via ISTA diagnostics when replaced; must use correct AGM with proper amperage. Acceptable parasitic draw is 30 milliamps. IBS sensor €100-300. Complex electrical architecture means expensive diagnostics at dealer.
Water pump / thermostat failure€800 - €1,800
Electric water pump integrated with thermostat, typically fails 70,000-100,000 km · more· less
N63 uses electric water pump integrated with thermostat housing. Symptoms: coolant warning light, engine overheating, poor cabin heating. Common failure 70,000-100,000 km. Integrated part costs €400-600. Labor approximately 6 hours due to accessibility in hot-V configuration. Overheating can cause head gasket failure (add €3,000-8,000). Replace at first sign of failure to prevent catastrophic damage.
Transmission mechatronic sleeve€1,500 - €3,500
ZF 8-speed generally reliable but mechatronic sleeves flatten causing harsh shifts · more· less
ZF 8HP transmission in M550i is generally excellent. Issues: harsh/delayed shifting when cold, transmission slipping, rough 2nd-to-1st downshifts, shift flares. Caused by worn fluid, mechatronic sleeve wear, solenoid issues. Sleeves flatten over time becoming stiff. Known rough until warm. Poor fluid maintenance accelerates mechatronic issues. Mechatronic replacement €1,500-3,500 at dealer. Regular fluid changes every 60,000 km crucial despite BMW "lifetime" claim. Software updates sometimes resolve issues.
Flex disc (guibo) vibration€300 - €600
Vibration dampener on transmission output wears, causes vibration at low speeds · more· less
Guibo (flex disc) connects transmission to driveshaft. When worn, produces terrible vibration throughout car, especially noticeable at low speeds and when starting from standstill. OEM part €198, aftermarket €83. Labor 1.5-4 hours depending on shop experience (€200-400). Hardest part is removing 21mm bolts - air tools help. Replace center support bearing at same time (similar labor). Total cost €300-600. Common wear item on high-performance BMWs.
Adaptive suspension issues€2,000 - €5,000
Air compressor solenoid sticks, damper control units fail, hydraulic leaks occur · more· less
G30 M550i with adaptive suspension prone to issues. Air suspension: compressor air release solenoid sticks (€20 solenoid, 5 min fix vs €2,000 dealer quote for compressor). Airbag failures drop car on bump stops. Adaptive dampers: hydraulic leaks from worn seals, control module failures, communication errors between damper units and VDM. Ride height sensors with ball-joint arms fail. Internal damper control unit failures require full EDC shock assembly replacement. Chassis warning lights intermittent. Complex diagnosis expensive at dealer.
Much improved over early N63, but complex and expensive to maintain
The N63TU2 engine in the 2017-2020 G30 M550i is significantly more reliable than the notorious early N63 (2008-2013) which had catastrophic timing chain and valve stem seal failures. BMW made substantial improvements with TU2. However, the hot-V turbo design still creates heat-related issues with coolant lines and seals. Budget €1,700-3,150 annually for maintenance. Not a car to own without warranty or substantial repair budget. Independent BMW specialist essential for reasonable costs.
Pre-Purchase Inspection Checklist
General checks
Service history
Complete BMW dealer or specialist records essential. Verify oil changes every 10,000 km maximum (BMW says 15,000 km, but shorter interval extends engine life). Check for Customer Care Package completion if 2017-2018 model.
Cold start test
Must start engine completely cold. Listen for timing chain rattle in first 30 seconds. Brief rattle (1-2 seconds) acceptable; persistent rattle (5+ seconds) indicates stretched chain requiring immediate €2,500-5,000 repair.
Test drive minimum 30 minutes
Include highway speeds. Watch for drivetrain malfunction warnings (wastegate issues), transmission behavior when cold vs hot, any unusual noises or vibrations.
Tires
Performance tires expensive (€800-1,200 per set). Check tread depth, age (date codes), uneven wear. Rear tires wear faster due to power/xDrive.
Specific for this vehicle
Check for coolant smell in cabin or engine bay
Distinctive sweet smell indicates turbo coolant line leak. Look for staining below turbos (valley area). Check alternator for coolant damage. This is the most common expensive failure on N63TU2.
Oil consumption test
Check oil level when cold. Ask seller about oil consumption between changes. More than 1 liter per 1,500 km suggests valve stem seal issues (€4,000-10,000 repair). Blue smoke after idling confirms.
Scan for fault codes
Use BMW-specific scanner (not generic OBD2). Look for P2ABA, P12C4, P12C6 (wastegate), timing chain codes, mechatronic codes. Check for stored codes even if warning lights off.
Cold start timing chain rattle
Critical test. Engine must be completely cold (sit overnight). Listen for rattle in first 30 seconds. Persistent rattle means stretched chain requiring immediate repair to prevent catastrophic failure.
Test all electrical systems
iDrive, parking sensors, cameras, adaptive cruise, head-up display, comfort access. Battery drain issues manifest as glitchy electronics. Verify battery recently replaced and properly registered.
Check for vibration at low speeds
Flex disc (guibo) wear causes vibration starting from standstill and at low speeds. Also check for driveshaft center bearing noise.
Adaptive suspension test (if equipped)
Check all suspension modes work. No warning lights. Car should not sit low on bump stops. Listen for air compressor running excessively. Test ride quality - harsh ride indicates damper issues.
Verify service campaigns completed
BMW had various campaigns for N63 engines including timing chain, fuel injectors, coolant lines. Contact BMW dealer with VIN to verify all completed. Customer Care Package critical for 2017-2018 models.
Brake and tire condition
Brake pads €270-500, rotors €450-900. Performance tires €200-300 each. Check for uneven wear indicating suspension/alignment issues. Verify no cracking on brake discs.
Recalls and Service Campaigns
N63 Customer Care Package (2017-2018)Verify completed
Timing chain extended warranty (early N63)Check with BMW
Turbo coolant line campaignVerify completed
Fuel injector campaign (covered under CCP)Check with dealer
Software updates (transmission, engine management)Verify current
Critical: Verify N63 Customer Care Package completion
BMW issued Customer Care Package for N63 engines covering timing chain, fuel injectors, and valve seals. Package extended coverage to 10 years/100,000 miles from manufacture date. Most 2017-2020 G30 M550i models now outside this coverage, but verify with BMW dealer using VIN. If CCP never performed, walk away or negotiate significant price reduction - these repairs can exceed €15,000.
Warranty Status
Factory warranty (2 years unlimited km in EU)Expired on all 2017-2020 models
Powertrain warranty (varies by market)Likely expired
BMW extended warranty availabilityCheck with dealer - age/mileage dependent
Third-party extended warranty€1,500-3,000/year
Strongly consider extended warranty
The M550i's complexity and high repair costs make extended warranty highly advisable. Single N63 engine failure out-of-warranty can cost €40,000 for replacement. Valve stem seals €4,000-10,000, timing chain €2,500-5,000, turbo issues €1,500-6,000. Many owners report they would not own G30 without warranty due to extreme repair costs. Independent warranty companies may exclude N63 engine due to known issues. Budget minimum €2,000 annually for unexpected repairs if no warranty.
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.