Mercedes-Benz E350 W213

The M264 engine has a documented defect involving premature wear of the exhaust valve guides and seat rings. Increased lateral forces during operation cause the valve guides to wear beyond specification, leading to poor valve sealing. Symptoms include engine misfires (typically codes P0300-P0304), rough idle, check engine light, and in severe cases, sudden power loss. The issue can appear as early as 50,000 km, though most failures occur between 60,000-100,000 km. Mercedes-Benz USA has extended warranty coverage to 15 years / 240,000 km for the exhaust valve system on 2018-2023 M264 engines. European warranty extension has not been officially confirmed to the same extent, but dealers have been performing goodwill repairs in documented cases. If not covered, cylinder head replacement costs €3,000-5,000 at an independent specialist and €5,000-7,000 at a Mercedes dealer. A class action investigation is ongoing in the US. When buying, always scan for misfire codes and check whether the cylinder head has already been replaced.

The EQ Boost system relies on a 48V lithium-ion battery that powers the integrated starter-generator and provides the electric boost function. The battery can degrade over time, causing 'Hybrid System Error' warnings, disabled start-stop, weak acceleration from standstill, and in some cases vehicle stalling. Multiple owners have reported failures within 3-5 years. A class action lawsuit has been filed in the US over repeated 48V battery failures across Mercedes models. Battery replacement costs approximately €1,500-2,500 including labor, as the unit is sealed and requires dealer-level diagnostics for initialization. The battery is expected to last 6-8 years under normal conditions, but hot climates and extended parking periods accelerate degradation. Ensure the start-stop system functions correctly during any test drive.

Like all direct injection engines, the M264 does not wash fuel over the intake valves. Oil vapors from the crankcase ventilation system bake onto valve surfaces over time, restricting airflow. Symptoms include rough idle, hesitation under acceleration, and increased fuel consumption. The buildup becomes noticeable between 60,000 and 80,000 km depending on driving patterns. Short trips and frequent cold starts accelerate the problem. Walnut shell blasting is the standard cleaning method, costing €500-900 at an independent specialist for a four-cylinder engine. This is considered preventive maintenance by most specialists and is recommended every 60,000-80,000 km. Regular motorway driving and using premium fuel help slow the buildup but cannot prevent it entirely.

The 725.0 9G-Tronic nine-speed automatic can develop jerky shifting behavior, particularly at low speeds between 1st-2nd and 2nd-3rd gears. Symptoms include harsh downshifts when slowing, hesitation when moving from neutral to drive, and occasionally delayed gear engagement. In many cases, a TCU software update from a Mercedes dealer resolves the issue (€200-400). However, if the valve body or mechatronic unit has degraded, repair costs increase significantly to €1,200-2,000. Regular ATF changes every 60,000-80,000 km help maintain smooth operation, despite Mercedes marketing the fluid as a lifetime fill. If ignored, shifting issues can progress to limp mode. During any test drive, pay attention to low-speed shifting quality over at least 20 minutes of varied driving.

AIRMATIC is optional on the E350 (standard on AMG models). If your car is equipped with it, the rubber air springs become brittle over time and develop micro-cracks. Symptoms include one corner sitting lower after overnight parking, the compressor running constantly, or suspension warning messages. Failure typically occurs after 80,000-120,000 km. OEM replacement per spring costs €600-900, with aftermarket alternatives from Arnott available for €300-500 per spring. The compressor can fail from overwork, adding €500-900 for replacement. A full overhaul (4 springs plus compressor) at a dealer can reach €3,000-3,500. Some owners convert to conventional coil springs as a permanent solution for around €800-1,200. If the car has steel springs, this issue does not apply.

Mercedes considers oil consumption of up to 0.5 litres per 1,000 km as normal for the M264 engine. Some owners report consumption exceeding this threshold, particularly on pre-2021 production engines. Causes include worn piston rings, valve stem seal degradation, or PCV system malfunction. If consumption is excessive (more than 1L per 2,000 km), a compression test and borescope inspection are recommended. PCV system repair costs approximately €500-800. Valve stem seal replacement runs €1,200-1,800. Piston ring replacement requires engine disassembly at €2,000-2,500. Regular oil level monitoring between services is essential. Using the correct MB 229.51 or 229.61 specification oil and maintaining 15,000 km or shorter change intervals helps preserve internal seal integrity.