BMW M40d
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 Torque
R6 diesel in the X4 — powerful and efficient.
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 5
A production defect in the IBS motor position sensor can cause ABS and DSC to fail. Affected vehicles produced June 2022 to August 2024. BMW replaces the integrated braking system free of charge (Recall 0034670200).
The G02's automatic gearbox shows problems with its adaptive shift logic under varying driving conditions. Juddering on pull-away and gear changes typically occurs from 70,000 km.
Tie rod ends, springs and dampers are flagged at TÜV inspections. The vehicle weight stresses suspension components more than on smaller models.
Diesel engines in the G02 are prone to particulate filter clogging when used predominantly for short trips. Regeneration requires longer motorway runs. A blocked DPF can trigger engine protection shutdown.
On the G02 as well, the electric tailgate motor often fails from 30,000–50,000 km. The tailgate then won't open on button press or jams when closing.