Used Mercedes-Benz S400

What to know before buying: Mercedes-Benz S400

From 2 forum threads and 1 press test · updated 12/10/2026

What the reviews say

• The 2009 S400 HYBRID combines a 3.5-litre V6, an electric motor and a seven-speed automatic; total output is 299 hp and stated consumption is 7.9 L/100 km.[1]one source
• The hybrid system operates almost seamlessly: the automatic is smooth, while the stop-start system restarts the engine quickly and gently.[3]one source
• The regenerative brake pedal feels unusual: initially soft, then spongy, before becoming more conventional deeper in its travel.[3]one source
• S400 CDI W220 owners praise its strong pull; one car covered 146,000 to 236,000 km without engine trouble when serviced on time and supplied with good fuel.[2]one source

Typical faults

• The S400 CDI W220 is reported to suffer from throttle-body assemblies and fuel supply pump problems.[2]one source

  S400 CDI

• On the S400 CDI W220, the timing chain and tensioners need watching; start-up noise may signal a chain replacement, mentioned by an owner at around 200,000 km.[2]one source

  200 000–200 000 km · S400 CDI

• On the S400 CDI W220, a failed copper injector seal can leak combustion gases and seize the injector; if neglected, the injector may break during removal.[2]one source

  S400 CDI

• One inspected S400 CDI W220 had cracking and delamination in the upper rubber sections of its front air struts, indicating possible near-term suspension expense.[2]one source

  S400 CDI

Which engine and version to take

• Pick the S400 HYBRID for efficiency and refinement: sources cite 7.9 L/100 km, near-seamless hybrid operation and no loss of luggage space.[1][3]

What to avoid

• Consider the S400 CDI W220 only after thorough diagnosis: the forum reports throttle, supply-pump, timing-chain and injector-seal issues, and notes that the engine is rare.[2]one source

What to check at the inspection

• Start the S400 CDI both cold and warm: it should fire immediately without noises that later disappear, as these may indicate timing-chain wear.[2]one source
• Scan the engine for faults, inspect it for oil leaks and confirm that it runs evenly and quietly.[2]one source
• During the test drive, check for even pull without excessive smoke or flat spots; turbo boost should be clearly felt without abnormal noises.[2]one source
• Remove the air filter and inspect around the injectors: black oily deposits may indicate a poorly seated injector or failed copper seal.[2]one source
• Check the turbochargers by removing their outlet boost pipes; the forum advises that these should be clean.[2]one source

Verdict

Sources

1. [1]iauto.lv — Uzsāk jaunās paaudzes Mercedes-Benz S-klases ... · forum
2. [2]forum.benzua.com — MB S400 CDI (W220) - нужна информация о двигателе · forum
3. [3]carsales.com.au — Mercedes-Benz S400 HYBRID 2009 Review - International · press

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