Mercedes-Benz E 450
Return to the inline-six after years of the M276 V6 — and the difference is immediately noticeable. Smoother, more even rev build-up, torque plateau from 1,600–4,000 rpm without any weakness. The 48V mild-hybrid system with integrated starter-generator (ISG) is not a marketing term: 16 kW of boost on pull-away fills turbo lag completely; measurable fuel saving in sail mode. When buying, check the 48V battery — failure costs 2,000–4,000 EUR, primarily affecting build years up to 2022. Electric coolant pumps can fail from 80,000 km. Change oil every 10,000 km, do not rely on Longlife — HPFP and camshaft adjusters are sensitive to old oil. Cold-start wastegate bushing rattle is by design and not a fault. Overall a very accomplished engine that holds 250,000 km without issues when maintained correctly.
W214 E450 — the Refined Generation
280 kW, 500 Nm — even more refined than the W213 predecessor. Inline-six running refinement at S-Class level for E-Class money. Under 8 litres in mixed driving with predominantly motorway is achievable. The most convincing petrol engine in the current E-Class, with better infotainment and more modern technology than the predecessor.
Engine Weaknesses 9
Frequently reported problem: 48V battery of the EQ Boost system fails and costs 2,000–4,000 EUR to replace. Design issue with earth connection in early vehicles.
Symptoms: EQ Boost deactivated, start-stop system failed, hybrid warning light, sporadic starting problems
The known Mercedes problem of leaking camshaft solenoids also affects the M256 (same solenoid technology as M276/M270). Oil migrates by capillary action and destroys lambda sensors and the ECU.
Symptoms: Lambda sensor fault codes, MIL, rough running. Multiple electrical faults simultaneously as it progresses
M256 shows elevated oil consumption from approx. 100,000 km, attributable to the PCV system and cylinder walls. Regular oil level checks necessary.
Symptoms: Dropping oil level, occasional bluish smoke after warm-up phase
The beltless M256 operates exclusively electric coolant pumps. Pump motors fail internally and trigger temperature warnings. Bleeding requires specialist diagnostic equipment.
Symptoms: Coolant temperature warning, irregular operating temperature, occasional overheating warning
The camshaft-driven high-pressure pump on the M256 can wear prematurely with irregular oil changes. Injectors can be damaged by metal debris.
Symptoms: Fuel pressure fault codes, rough idle, starting problems, hesitation under load, elevated fuel consumption
With predominantly short-trip use the OPF cannot fully regenerate. Power drop and elevated consumption result. Virtually no risk for motorway drivers.
Symptoms: Power drop at higher load, elevated fuel consumption, occasional particulate filter warning, engine runs rougher
The M256 uses Camtronic variable valve actuation — same technology as M276/M270 with documented failures. Wear on the adjustment unit or solenoid valve is possible. Oil quality is decisive.
Symptoms: Hesitation at low rpm, camshaft position sensor fault code, rough idle, engine warning with power reduction
Direct injection on the M256 inline-six causes carbon deposits on intake valves. Walnut blasting every 60,000–80,000 km recommended.
Symptoms: Hesitation in the lower rev range, rough idle, sporadic misfires on cold start
Rattling on cold start from the wastegate guide bush with design-inherent play. BorgWarner states this is necessary so the wastegate does not stick at operating temperature. Mercedes classes it as state of the art — not a defect.
Symptoms: Rattling or clattering in the first seconds after cold start, disappears after warm-up
Vehicle Weaknesses 6
Faulty MBUX software can deactivate lane-keep assist and emergency braking assistant. Affects production 10.11.2021–29.01.2024.
MBUX 3.0 shows complete screen blackouts with loss of climate control, navigation and vehicle functions while driving.
MBUX 3.0 starts in emergency mode with barely any functions available. Spotify/Apple Music show only a loading screen. Mainly affects early production vehicles from 2023.
The optional AIRMATIC air suspension is prone to pressure loss at the air spring bellows or pressure hoses. Vehicle sags on one side.
MBUX 3 system can fail completely — only the speedometer remains functional. Spotify, Apple Music and navigation fail to load. Software updates are applied regularly.
Rattling noises from doors and interior trim appear shortly after delivery. Individual vehicles with heavily rattling passenger door from the factory.