BMW 640d F12

The N57 engine's timing chain sits at the rear of the engine, meaning the gearbox must be removed for access. Over time, the chain stretches and the hydraulic tensioner can lose pressure overnight, producing a metallic rattle for the first 1-3 seconds after a cold start. Typically observed between 130,000 and 200,000 km, though early failures at 100,000 km have been documented. Unlike the N47 four-cylinder, the N57 usually gives audible warning before catastrophic failure. Independent specialists charge approximately €1,500-2,500 for the replacement, while BMW dealers quote €2,500-3,500. Most specialists recommend replacing the oil pump chain and big-end bearing shells during the same job, adding approximately €500-800 to the total bill.

The N57 uses thinner-walled main bearings than the older M57 engine it replaced. Under sustained high load or with inadequate oil change frequency, these bearings can degrade faster than expected. Failures tend to appear from 120,000 km onward and are strongly linked to BMW's long 25,000 km oil change intervals. Many specialists now recommend changing oil every 10,000-15,000 km as a preventive measure. Symptoms include a deep rumbling noise at low RPM and metallic particles in the oil. If caught early, bearing replacement costs €2,500-4,000. If the crankshaft is scored, a full engine rebuild or replacement can reach €5,000-6,000. The 640d's twin-turbo variant sees higher loads than the single-turbo 330d/530d, making frequent oil changes even more important.

BMW has issued multiple recall campaigns for this problem, initially in 2018 and expanded several times through 2022, ultimately affecting over 500,000 vehicles in Germany alone. The N57 diesel in the 640d is included in these campaigns. When the EGR cooler leaks internally, glycol coolant mixes with hot exhaust soot deposits, potentially creating smouldering particles that can melt the plastic intake manifold. Warning signs include unexplained coolant loss, reduced engine power, and exhaust smell in the cabin. The repair is free under the recall, but re-occurrence has been reported by some owners. If the recall has not been completed and the manifold is damaged, out-of-pocket costs run €800-1,500. Always verify recall completion with BMW before purchasing.

The 640d's twin-turbo setup uses a small high-pressure turbo and a larger low-pressure turbo working in sequence. The electronic actuator on the high-pressure turbo is the most common failure point, typically sticking from carbon buildup after 130,000 km. Symptoms include intermittent power loss, limp mode, and boost-related fault codes. Cars driven gently in urban traffic are more susceptible. BMW does not sell the actuator separately, but specialist turbo shops can rebuild or replace just the actuator for €500-800. If the turbo internals are damaged, full turbo replacement runs €1,500-2,500 including labor. Driving at varied engine loads and avoiding exclusively short trips helps prevent actuator sticking.

The high-pressure fuel pump (HPFP) can fail catastrophically, with internal components wearing and generating metallic debris that contaminates the fuel rail, injectors, and fuel lines. BMW issued recall 21V-586 for 2014-2018 diesel models and extended the HPFP warranty to 10 years or 193,000 km on affected engines. If the pump fails outside warranty coverage, the repair bill is substantial because the entire fuel system may need flushing or replacement. A revised Bosch pump and new injectors cost approximately €1,200-1,500 in parts alone, with labor pushing the total to €2,000-3,000. If the metal contamination has spread throughout the system, costs can reach €4,000-5,000. Verify the recall status and HPFP warranty eligibility with BMW before purchasing.

The ZF 8HP70 automatic transmission is fundamentally well-engineered but BMW's guidance that it is filled for life leads many owners to skip fluid changes entirely. Without regular fluid replacement (recommended every 60,000-80,000 km by independent specialists), the mechatronics unit's valve body and solenoids accumulate debris and fail. Symptoms include harsh 2-3 upshifts, delayed engagement, or complete loss of drive. Pre-LCI cars (2011-2014) are slightly more susceptible, with failures documented from 80,000 km onward without fluid changes. The repair costs €1,500-2,500 for a mechatronics overhaul at a specialist, or €2,500-3,500 for a full rebuild at BMW. Regular transmission fluid changes dramatically reduce this risk.

The F12 convertible uses an electrically driven hydraulic pump to operate the soft top. Over time, the pump's internal seals can degrade and the motor weaken, resulting in gradual pressure loss. Symptoms include slow or incomplete opening/closing of the roof, unusual noises during operation, and eventually complete failure to operate. Specialist rebuild services charge €600-900 for pump reconditioning with upgraded seals and relays. Full pump replacement at BMW costs €1,200-1,500 including labor. This issue does not affect the F13 coupe or F06 Gran Coupe variants. Regular use of the mechanism helps keep seals lubricated. Cars stored for extended periods with the top in one position are more susceptible.

Most 640d models are equipped with EDC (Electronic Damper Control) adaptive suspension. The dampers contain magnetorheological or electronically controlled valves that adjust firmness. These dampers have a finite service life and commonly begin failing between 80,000 and 120,000 km, with oil misting or leaking from the damper body being the telltale sign. Symptoms include uneven ride quality, suspension warning messages, and a noticeable difference in damping between corners. OEM replacement costs approximately €500-700 per damper at an independent specialist (parts and labor). Aftermarket EDC-compatible dampers from Bilstein or similar brands offer a less expensive alternative at €350-500 per corner installed.