Popular compact executive sedan with engaging rear-wheel drive dynamics. However, the four-cylinder N46 (2005-2007) and N43 (2007-2012) engines have significant reliability concerns. Both suffer from timing chain tensioner failures causing cold-start rattle, with the N46 prone to oil leaks and valve stem seal issues, while the N43 has expensive piezo injector failures and misfiring problems. The six-cylinder N52 engine (325i/328i/330i) is far more reliable. Expect higher maintenance costs than rivals, but parts are widely available. Buy only with complete service history and budget for repairs.
The tensioner has a release valve that weakens over time, allowing oil pressure to bleed off overnight. This causes a distinctive rattle for 1-30 seconds on cold start, typically occurring between 60,000-100,000 km. If ignored, the timing chain guides break down and clog the oil pickup, leading to oil starvation and catastrophic engine failure. BMW introduced an updated tensioner part in March 2007, but both N46 and N43 engines remain susceptible. Chain replacement requires significant labor (10-12 hours) as the engine front must be disassembled. Cost includes chain, tensioners, guides, and sprockets. Some engines have failed as early as 40,000 km.
Valve stem seal deterioration€1,400 - €2,000
Seals become brittle, cause blue smoke at startup and oil consumption · more· less
Valve stem seal failure is very common on BMW 4-cylinder N42/N46/N43 engines, even with only 50,000 km. Extended BMW oil change intervals combined with poor-quality seals accelerate failure. Symptoms include blue smoke on cold start that disappears when warm, and excessive oil consumption (1+ liter per 1,000 km). The seals can be replaced without removing the cylinder head using compressed air methods, but it's a skilled job requiring 8-10 hours labor. The last two seals on cylinder 4 are particularly difficult to access. Parts cost approximately €150-250, with most cost being labor. This is more common on N46 than N43 engines.
Piezo injector failure (N43 only)€1,200 - €2,400
Direct-injection piezo injectors fail, cause lumpy idle and misfires · more· less
The N43 engine (2007-2012) uses expensive piezo crystal injectors for direct injection. These wear out from high combustion temperatures (2,500°F+) and typically fail between 60,000-120,000 km. Symptoms include rough idle from cold, misfire on acceleration, and diagnostic codes. New injectors cost €300-400 each (4 required), but availability is poor as they're no longer manufactured. Used injectors are available for €75-100 each. Some specialists offer injector refurbishment. The N43 became problematic just 1-2 years after launch due to injector failures. Tool rental shops in the UK often have 3 N43 timing chain kits out simultaneously, indicating widespread issues.
Oil filter housing gasket leak€300 - €900
Gasket fails, causes oil leak on left side of engine · more· less
One of the most common oil leak sources on the E90 320i. The oil filter housing gasket deteriorates over time, causing oil to leak down the left side of the engine. Often misdiagnosed as an oil pan gasket leak. The gasket kit costs only €25-40 and includes new mounting bolts and oil pressure switch, but labor is 2-3 hours due to cooling system components that must be moved. DIY-friendly repair that can save €200-500 in labor costs. Should be inspected during any service as it will eventually fail on all N46/N43 engines with age.
Electric water pump failure€800 - €1,200
Pump fails typically around 80,000 miles, causes overheating · more· less
BMW uses an electric water pump integrated with the thermostat housing. Common failure around 80,000 miles (130,000 km) or 9-10 years regardless of mileage. Symptoms include coolant warning light, engine overheating, or poor cabin heating. When replacing the water pump, the thermostat should also be replaced (both integrated in same assembly). Parts cost: genuine BMW pump €500+, aftermarket Pierburg €300, thermostat €65-110. Labor approximately 2-3 hours. The combined water pump and thermostat job typically costs €800-1,200 depending on parts choice. Preventive replacement recommended at high mileage.
VANOS solenoid clogging€400 - €600
Solenoids clog with oil sludge, cause rough idle and check engine light · more· less
The VANOS (Variable Valve Timing) system uses solenoids that can fail due to o-ring degradation or clogging with dirt and oil sludge. Early E90 models were particularly affected. Symptoms include sluggish acceleration, loss of power, rough idle, increased fuel consumption, and check engine lights with codes 29F4/29F5. BMW released a software update with a special VANOS cleaning cycle to address contamination. Solenoids cost approximately €100 each (2 required), and replacement takes only 20 minutes. However, clogged solenoids often indicate poor oil change history. BMW recommends replacing o-rings every 50,000 miles. Can sometimes be cleaned rather than replaced.
Ignition coil failure€300 - €500
Coils fail from heat damage, cause misfires and rough running · more· less
Ignition coils are an extremely common failure on BMW engines, subject to heat damage and electrical overload. If the car throws a misfire code, it's often an ignition coil. Symptoms include difficulty starting, misfiring, loss of power, and rough idle. Coils should be replaced every 40,000-60,000 km as preventive maintenance. Aftermarket coils cost €30-40 each, while OEM parts are €60-80 each. When one coil fails, it's recommended to replace all four as the others are likely near end-of-life. Total cost for 4 aftermarket coils plus spark plugs: €200-300 DIY, or €400-600 at a garage including labor. This is a wear item that will need attention multiple times over the car's life.
Window regulator failure€350 - €700
Plastic drive dog breaks, causes window to stick or fall down · more· less
Window regulator failure is a well-known E90 problem. The cable inside comes detached or the plastic drive dog breaks. Symptoms include stuck windows, slow operation, or windows falling into the door. BMW dealers charge €450-680 per window. Independent shops charge €350-500. The actual failing component is often just the drive dog (small plastic piece), which costs €15-20 for a repair clip kit. If you can access the door panel yourself, it's a €75 DIY fix. Front windows fail more often than rear. Most E90s over 10 years old will experience at least one window regulator failure.
Control arm bushing wear€600 - €1,200
Bushings wear out, cause squeaking over bumps and uneven tire wear · more· less
Front suspension control arm bushings typically wear out around 100,000 km or every 3-4 years. Symptoms include squeaking over bumps, knocking sounds when severely worn, uneven tire wear, and the vehicle pulling to one side. On some E90 models, bushings are permanently installed in the control arms, requiring full arm replacement rather than bushing-only replacement. Dealer pricing: €665-1,025 for bushing replacement, or €960-1,225 for complete control arm replacement. Independent shops charge €500-800. A wheel alignment is required after replacement (add €80-120). OEM replacement is recommended as aftermarket bushings wear faster.
Valve cover gasket leak€400 - €800
Gasket deteriorates, causes oil leak at top of engine · more· less
The valve cover gasket (rocker cover gasket) protects the valves and rocker arms at the top of the engine. Leaks become more common after 60,000 miles. Heat and age cause the gasket to become brittle and crack. Oil leaks down the side of the engine and may drip onto exhaust components, causing burning oil smell. The gasket itself costs €50-80, but labor is 2-3 hours due to components that must be removed for access. Total cost at BMW dealer: €500-800. Independent shop: €350-550. Can be combined with spark plug and ignition coil replacement to save labor costs. All N46/N43 engines will eventually need this gasket replaced.
Below-average reliability with expensive repairs ahead
The N46 and N43 four-cylinder engines have significantly worse reliability than the six-cylinder N52 used in 325i/328i/330i models. Both engines suffer from timing chain issues, though the N43 (2007-2012) has additional problems with expensive direct-injection piezo injectors. Forum consensus strongly recommends avoiding four-cylinder E90 models in favor of six-cylinder variants. One owner reported the N42B20 has 7% better fuel economy over the M54B25 six-cylinder, but 600% more repairs. Only purchase if you have complete service history, budget €1,000-1,500 annually for repairs, and can verify timing chain condition before buying.
Pre-Purchase Inspection Checklist
General checks
Complete service history
Essential to verify oil changes every 10,000-15,000 km maximum. Extended intervals accelerate timing chain and seal failures.
Cold start test
Engine must be completely cold (8+ hours parked). Listen for rattling in first 30 seconds. Any rattle lasting more than 2 seconds indicates timing chain issues.
Oil consumption check
Ask seller about oil consumption. More than 1 liter per 5,000 km indicates valve stem seal or piston ring problems.
Exhaust smoke test
Blue smoke on cold start indicates valve stem seal failure. Blue smoke on deceleration indicates worn piston rings.
Extended test drive
Minimum 30 minutes including highway speeds. Check for misfires, hesitation, and warning lights.
Specific for this vehicle
Timing chain cold-start rattle
Most critical check. Start engine completely cold and listen carefully for rattling for first 30 seconds. Any rattle indicates chain stretch and tensioner wear requiring immediate attention.
Oil leak inspection at oil filter housing
Check left side of engine for oil residue. Oil filter housing gasket fails on nearly all high-mileage examples.
N43 injector misfire test (2007-2012 models)
Start cold engine and feel for lumpy idle or hunting revs. Drive and check for hesitation on acceleration. These indicate expensive piezo injector failure.
Check engine management light
Use OBD scanner to check for stored codes even if light is off. Look for VANOS codes (29F4, 29F5), misfire codes, or NOx sensor faults.
Coolant system check
Verify coolant level, check for brown/milky appearance. Look for leaks at water pump and thermostat housing. These fail around 130,000 km.
Test all four windows
Operate each window fully up and down multiple times. Listen for grinding or slow movement indicating regulator wear.
Suspension noise test
Drive over speed bumps at slow speed with windows down. Squeaking or knocking indicates worn control arm bushings.
Verify VANOS recall completion
2009-2011 N51/N52K/N52T engines had VANOS bolt recall (14V-176). Use VIN to verify with BMW dealer if recall work completed.
Recalls and Technical Service Bulletins
VANOS adjustment unit oil leakage (2009-2011)Recall 14V-176
Contact BMW with VIN to verify all recalls completed. Call BMW Recall Hotline: (800) 525-7417 or check NHTSA database with VIN.
Warranty Status
Original factory warranty (4 years/50,000 miles)Expired on all E90s
BMW Extended WarrantyNot available (too old)
All E90 320i models (2005-2012) are outside factory warranty. Extended warranty from BMW is not available for vehicles this old. Consider independent warranty providers, but most exclude pre-existing conditions and high-mileage engines. Budget for repairs without warranty coverage.
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.