Mercedes-Benz GLS 400d

The vacuum-controlled coolant pump can develop leaks between the coolant and vacuum circuits. Coolant enters the EGR solenoid valves; an electrochemical reaction creates a fire hazard.

The Bosch CP4 high-pressure pump is more sensitive to fuel contamination than its predecessors. Poor diesel quality can damage the pump and injectors.

Symptoms: Power loss, hesitation, injection system fault codes, in severe cases engine damage from metal swarf

The switchable coolant pump does not reliably seal between the coolant and vacuum circuits. Coolant can overheat electrical solenoid valves — fire risk. Campaign code 2090008.

Symptoms: No direct driver symptoms — preventive recall. Possible coolant loss, electrical faults, unusual odour

Early OM656 units had overly soft roller rocker arms. From engine number 80278367 (10/07/2018) a reinforced version was fitted. Older engines develop camshaft wear and timing chain problems.

Symptoms: Clattering tick in the valvetrain, especially on cold start, increased oil consumption, CEL, rough running

The variable valve lift system Camtronic shows failures at solenoid valves and actuators, especially up to 2022. Camshaft wear generates metal particles in the oil.

Symptoms: Rough idle, knocking noises while driving, elevated oil consumption, variable valve train fault code

DPF, EGR and SCR/AdBlue system are sensitive to frequent short-trip driving. Premature blockages with warning lights are common.

Symptoms: Engine warning light, DPF warning lamp, power reduction in regeneration mode, elevated AdBlue consumption

The 48V earth connection under the passenger seat was fastened with insufficient torque. High currents raise junction temperature — fire risk. 52,363 vehicles affected.

During gentle braking with gear change 7→6 and simultaneous 48V recuperation, the engine can stall. 260,658 vehicles worldwide affected.

Incorrectly routed A/C condensate drain hoses allow water ingress into the interior. Contact with electrics causes short circuits. 171,463 vehicles affected.

Leaks in the air suspension system cause the GLS to sag. Air spring bellows, lines and compressor are the most common weak points.

MBUX shows crashes during extended operation (black screen). Total failures occur especially after long drives over 400 km. Software updates often only provide temporary relief.