Mercedes-Benz S 350 d
Modern inline-six diesel with aluminium block and steel pistons. Efficient and powerful, few known weaknesses to date. Timing chain long-lived.
Diplomat Diesel S 400 d
210 kW diesel in the W223 glides almost silently. The S-Class here is a masterpiece of comfort, driving fun is not a criterion.
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 6
In early production of the W223 at Plant 56 Sindelfingen, the inner tie rods were fitted the wrong way round on approximately 1,400 vehicles. Tie rod failure could compromise steering ability.
A fault in the voltage converter software caused the ESP control unit to incorrectly detect a malfunction and deactivate itself. 23,517 S-Class vehicles (model year 2020–2021) worldwide were affected.
The MBUX system shows sporadic complete failures of both screens. Cause is software and hardware faults in the head unit. OTA updates required.
The W223 has high quiescent current draw through permanent internet connections and app queries. After 5–7 days standing, the app reports a critical battery warning.
The electric ABC system with 48V technology shows calibration problems and software faults on early build years. Specialist diagnosis at Mercedes required.
Mercedes recalled the W223 due to a software fault in the secondary electrical system voltage converter. The software could cause the secondary battery to discharge.