Mercedes-Benz R 350
Four-valve V6 in two basic variants: 3.5L naturally aspirated (DES 35, 185–225 kW) with direct injection and stratified charge — refined, linear, no classic naturally aspirated feel. And the 3.0L BiTurbo family (DEH 30 LA, 245–295 kW) with Nanoslide coating, twin turbochargers and water-air charge air cooler. The BiTurbo sings sonorously from 2,500 rpm and screams at the top — exceptional for a V6. Weak points: timing chain wears early when oil change intervals are pushed. Oil cooler in the V-block doesn't seal forever. Camshaft solenoids leak. On the 3.5L stratified-charge variant add NOx sensor failures from short-trip use. Early DES 35 (2011–2013) had piston slap issues. The BiTurbo unit with Nanoslide is considered more robust. Maintained with short oil change intervals (10,000–12,000 km) the engine easily lasts beyond 200,000 km.
V6 in the Spaceship — Power Is There, Fun Is Not
306 hp V6 moves over 2.2 tonnes of luxury MPV smoothly and quietly. Not a driver's car, but no shortage of power either. The all-wheel drive and air suspension make the R 350 an excellent long-distance transporter. Consumption 13–15 litres, running costs high. For families who need space and V6 refinement — not for enthusiasts.
Engine Weaknesses 10
Known weak point: the oil cooler gasket in the V-block of the M276 ages and starts leaking. Repair is extremely labour-intensive because the engine must be partially disassembled — cost €1,700–3,800.
Symptoms: Oil spots under the vehicle, rainbow sheen on wet road, dropping oil level, oil smell
Known damage pattern on all newer Mercedes engines: solenoid valves leak, oil migrates into the wiring harness. First the lambda sensors die, then the ECU. Repair documented up to €1,970.
Symptoms: Check engine light with camshaft fault code, lambda sensor failure, oil film on connectors, in extreme cases ECU failure
On early M276 DES 35 (build years 2011–2013) pistons can loosen due to cylinder bore wear. Knock noise on cold start, worst case engine damage.
Symptoms: Clacking and knocking on cold start from the engine area, getting louder over time, rough idle when cold
The two-stage chain drive system of the M276 receives insufficient oil on early engines, leading to premature chain wear.
Symptoms: Rattling on cold start, rough idle, in the worst case chain jump
The M276 has a plastic thermostat housing that cracks with age and loses coolant. The thermostat itself can also fail open.
Symptoms: Coolant loss, puddle under the vehicle, fault code P0128, engine runs too cold on motorway, temperature gauge fluctuates
The M276 PCV system with oil separator is known for failures from defective membranes or blocked valves. Increased oil consumption and power loss from false air ingestion.
Symptoms: Noticeably rising oil consumption, blue smoke from exhaust, crankcase breather fault code P052E, power loss
On the M276 DES 35 (stratified-charge variant) the NOx sensors in the exhaust stream fail. Moisture accumulates at the sensor — short-trip driving prevents it from burning off. Repair costs €900–1,200 per sensor.
Symptoms: Check engine light, NOx sensor fault code, possibly increased fuel consumption and harder starting
The exhaust manifold can crack from thermal shock — especially on sportily driven examples and early build years. Welding repair is possible but not lasting.
Symptoms: Unusually loud exhaust note, power loss, exhaust smell in the engine bay or cabin, incorrect lambda sensor readings
On M276 BiTurbo variants, the wastegate linkage on the turbochargers can develop play and rattle. A progressively louder metallic noise from the turbo area. Turbocharger replacement required.
Symptoms: Metallic clattering and rattling from the engine area, especially under load, gets worse over months, boost pressure fault code
Direct injection on the M276 V6 causes carbon deposits on the intake valves. Cleaning is necessary at higher mileages.
Symptoms: Stumble when accelerating from part throttle, rough idle, slight increase in fuel consumption
Vehicle Weaknesses 7
The Airmatic air spring bellows develop leaks and cause the vehicle to sink. The vehicle sits lower on one side when parked. Arnott replacement bellows approximately €200; workshop costs up to €1,900.
The 7G-Tronic gearbox does not pair well with diesel models; gearbox calibration is rough. At higher mileages torque converter defects occur; 3rd and 4th gear clutches burn out. Gearbox oil flush every 60,000 km recommended.
The Airmatic air suspension compressor wears at high mileage, particularly if the air spring bellows were already leaking and the compressor had to run continuously. Replacement compressor €400–700; expensive to fit.
Design-related water ingress into the boot or footwell damages connectors. Rear SAM control unit costs approximately €1,100 and fails when wet.
Rust appears on doors and black-painted chassis components. First two model years (2005–2006) particularly prone. Improved from 2008/2009 onwards. Avoid early vehicles if possible.
Doors and tailgate show rust perforation even on younger examples. Water ingress via defective seals promotes corrosion from the inside. Body shops quote €1,500–3,200.
The sunroof motor and gearbox skip and jam. Weak on-board electrical system due to battery problems. Steering knocks from worn joints. Wind noise from poorly seated seals.