BMW 120d E87

The N47 engine positions its timing chain at the rear, between engine and gearbox. The chain, guides, and tensioner are prone to premature wear. BMW fitted an excessively sharp-edged crankshaft sprocket from the factory, causing accelerated chain wear. Cars produced between March 2007 and January 2009 are most severely affected, though the issue persists across the N47 range. BMW revised components in 2009 and again in 2011, significantly improving but not eliminating the problem. Symptoms begin with a metallic rattle on cold start lasting 1-30 seconds. Once audible, the chain has already stretched significantly. Replacement requires gearbox removal and costs approximately €1,500-2,750 at an independent specialist in Western Europe. If the chain snaps, it causes catastrophic valve-piston contact requiring engine replacement at €3,500-7,000. Prevention: change oil every 10,000 km (not BMW's recommended 25,000 km long-life interval) using quality 5W-30. The 120d's higher output (177 hp) compared to the 118d (143 hp) puts slightly more stress on these components.

BMW issued a major recall affecting approximately 800,000 diesel vehicles worldwide due to defective EGR coolers. Coolant can escape from the cooler and combine with diesel soot accumulation at high temperatures, potentially causing the intake manifold to melt and, in rare cases, vehicle fires. The recall affects all N47-powered models including the 120d E87. BMW has acknowledged that prior corrective actions were inadequate, and an optimized cooler unit from a different supplier has only been used since 2022. The recall repair is free at BMW dealers, but many cars may still not have had it completed. If the recall has been done, cost is zero. If the car needs repair outside the recall (unlikely but possible), EGR cooler and valve replacement costs €600-1,500 at an independent workshop. This is a safety-critical item that must be verified before purchase.

The N47 intake manifold contains plastic swirl flaps that control airflow to optimize combustion. Over time, engine heat and vibration cause the plastic to become brittle. The flaps or their mounting clips can break loose and be ingested into the combustion chamber, causing piston damage, valve damage, and potentially destroying the turbo on the way out. If caught early, preventive blanking with aluminium plates costs just €20-40 for parts plus approximately one hour of labor (€100-150 total). If swirl flap fragments enter the engine, repair costs escalate dramatically: cylinder head repair at a specialist costs approximately €2,000-3,000, while a new engine from BMW runs €8,500-13,500 fitted. Preventive blanking is strongly recommended on any N47 that has not already had this done. By 150,000 km, the risk becomes significant.

The N47-powered 120d has a DPF that requires sustained highway driving above 60 km/h to regenerate. Cars used mostly for short urban trips accumulate soot faster than the filter can burn it off. Failed regenerations lead to a blocked DPF, causing power loss, increased fuel consumption, and warning lights. Professional DPF cleaning costs €200-350. If the filter is ash-saturated, back-flushing runs €400-600 or full replacement costs €1,000-1,800. Using a diagnostic tool to check soot loading before purchase is highly recommended. Cars with regular motorway use rarely experience this problem.

The N47 turbocharger uses an electronically controlled wastegate. The actuator mechanism can stick from carbon buildup, particularly on gently driven cars or those used only for short trips. The actuator spring is also prone to premature failure due to insufficient lubrication. Symptoms include EPC warning light, limp mode, significant power loss, and up to 50% increased fuel consumption. BMW does not sell the actuator separately, so their quote includes full turbo replacement at €1,500-2,500. Specialist repair services can rebuild the actuator for €400-600. Regular spirited driving and highway use helps prevent carbon buildup on the vanes. The 120d's higher output means the turbo works harder than in the 118d, though failure rates are similar.

Manual-equipped 120d models develop clutch judder when moving off, especially on inclines and when cold. The dual mass flywheel wears and develops excessive play, producing vibration through the pedal and drivetrain. The 120d's 350 Nm of torque (compared to the 118d's 300 Nm) puts more stress on the DMF and clutch assembly. Combined replacement costs €800-1,500 at an independent specialist, with parts (flywheel €250-400, clutch kit €150-250) plus approximately 6.5 hours of labor. This typically becomes necessary between 80,000-130,000 km depending on driving style. Urban stop-start driving accelerates wear significantly.

The E87 rear subframe is prone to corrosion on its lower edges where it catches stone chips, salt, and wheel spray. The problem is accelerated in coastal areas and regions that use road salt. Several E87 owners have reported subframes corroding so severely they snapped, damaging brake lines. Finding a rust-free replacement subframe is difficult, as most used ones are already corroded. Preventive treatment involves wire brushing surface rust and applying wax-based rust inhibitor every two years (€50-100). Professional sandblasting and POR-15 coating costs €300-500. Sourcing and fitting a replacement subframe costs €800-1,500 including labor. Powder coating a new subframe before installation is the best long-term solution.

The E87 boot area is prone to water ingress through rectangular vent panels behind the trim and through poorly sealed rear light housings. Water accumulates and soaks the PDC (parking distance control) module housed in the right-hand side of the boot. A waterlogged PDC module sends corrupted signals on the CAN bus, causing cascading electrical faults including instrument cluster failure, loss of speedometer and rev counter, and random warning lights. DIY fix involves resealing the vents and light housings (€10-20 in sealant). Drilling a small drain hole in the bung below the PDC module prevents reoccurrence. If the PDC module is corroded beyond repair, replacement costs €150-300. If other modules are affected by CAN bus interference, diagnosis and repair can reach €500.