Mercedes-Benz G 400 d
Modern inline-six diesel with aluminium block and steel pistons. Efficient and powerful, few known weaknesses to date. Timing chain long-lived.
Diesel Sovereignty
Powerful diesel with 250 kW in the G. Sovereign progress, but the G lives on image, not handling.
Engine Weaknesses 6
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
Vehicle Weaknesses 7
On vehicles with DISTRONIC PLUS, a CAN bus fault can interrupt coordination between DISTRONIC and ESP. The vehicle then maintains its current speed regardless of the situation.
At warm ambient temperatures a faulty brake control unit can trigger limp mode with a brake fault warning. Affects W463a from 2019. Replacement of the control unit required.
The window channel rubbers are not painted inside from the factory and often begin to rust within a few years. Window frames, roof rails and tailgate hinges are all at risk.
On the W463a, moisture can penetrate headlights and other lamp units. Without immediate resealing, secondary electrical damage follows.
MBUX system shows sporadic software and connectivity issues. Diagnosis complicated by Xentry system as proprietary protocols restrict external diagnostic tools.
The MBUX system occasionally freezes or becomes unresponsive. Climate control and seat adjustments can be partially affected. Software updates resolve some issues.
Thin paint layer and poor door panel finish reported. Warranty claims are occasionally rejected.