BMW 840d xDrive
Modular straight-six diesel with up to 340 hp in the M version. Extremely smooth and torquey; DPF and SCR catalytic converter are the main wear points.
Diesel GT
Inline-six diesel in a coupe — compelling for long-distance runs.
Engine Weaknesses 5
EGR cooler can fail and allow coolant into the intake tract. Documented cases of engine damage shortly after EGR cooler replacement.
Symptoms: Coolant loss, white smoke, engine check light, overheating
Early B57 models (from about 2015/16) show chain elongation with rattling noises on startup. Timing chain replacement requires engine removal. Repair costs comparable to the N57. Significantly rarer from 2018 models.
Symptoms: Metallic rattling on cold start, especially at low temperatures; subsides after warm-up; in extreme cases engine stumble
Bearing damage occurs in the bi-turbo system at higher mileage. Turbine blades can break off and cause engine damage. Frequently encouraged by insufficient oil change intervals.
Symptoms: Whistling or howling under load; blue exhaust smoke; power loss; MIL; in extreme cases sudden power loss from turbo failure
The EGR valve cokes up with frequent short-trip driving and becomes stiff. Stumbling on cold start is characteristic. BMW carried out a voluntary service action.
Symptoms: Stumbling and hesitation on cold start until the engine warms up; power loss; 'Drivetrain malfunction' message; black smoke; EGR valve fault
NOx sensors and SCR dosing unit fail after about 100,000 km or through AdBlue crystallisation. Fault code 26F500 is typical. BMW repairs often cost 2,000–4,000 EUR as entire systems are replaced.
Symptoms: MIL with message 'AdBlue system faulty' or 'Emission system fault'; fault code 26F500; engine runs normally but warning persists
Vehicle Weaknesses 14
The optional laser headlights cannot be repaired when faulty — they must be completely replaced. A single headlight costs around 5,700 € at BMW; total including fitting and calibration is 5,000–7,000 € per side.
The B58 in the 840i G14 tends to coolant loss through faulty heat exchangers and cracked plastic radiator fittings.
Like the G14, the G15's optional laser headlights cannot be repaired when faulty. A single headlight costs around 5,700 € plus ~1,000 € for fitting and programming.
Like the G15, the G16's optional laser headlights cannot be repaired when faulty. A single headlight costs ~5,700 € plus fitting and programming.
The G14's adaptive suspension shows damper wear at higher mileages. Standard dampers can be fitted as a cheaper alternative but require ISTA coding.
The adaptive suspension shows damper wear above 100,000 km. At over 1,800 kg, wear accelerates.
Faulty electronics in the comfort access door handle can cause a short circuit on the CAN bus line and elevated battery drain.
The iDrive 7 system shows sporadic navigation and Apple CarPlay crashes. GPS coordinates occasionally shown incorrectly. System was not updated to OS8.
M Sport or M Performance brakes tend to squeal heavily in city traffic and exhibit slight brake judder. Inherent to the pad material.
iDrive 7 shows sporadic system crashes, incorrect GPS data, and Apple CarPlay freezing. System was not updated to iDrive OS8 even after the facelift.
The deep front bumper on the G15 is particularly prone to stone chips. Paint thickness is described as below average for this price bracket. PPF is standard practice for many owners.
The G16's flat coupé roofline limits rear headroom. On older examples, creaking noises also emerge from the rear cabin.
The G16's iDrive 7 shows the same stability issues as the G15: sporadic CarPlay crashes, GPS errors, and occasional audio dropouts.
Same issue as the G15: M Sport brake pads are inherently prone to squealing at low speeds.