Mercedes-Benz E 500
4.7-litre BiTurbo V8 with direct injection (CGI), 90-degree bank angle and hot-V layout — turbos sit between the cylinder banks. Timing chain and tensioners are the first thing to check on used examples: cold-start rattle is a warning sign. Alusil bores react badly to wrong oil or extended intervals; piston slap develops gradually from oil film loss, often triggered by fuel-washing injectors. Ignition coils rarely last beyond 120,000 km. The oil separator should be checked after 100,000 km — when faulty it forces oil vapour into the intake and accelerates intake valve carbon build-up. Sound character: subtle BiTurbo rumble, no naturally aspirated roar. Shorten maintenance intervals to 10,000 km, oil MB 229.5 with low Noack value. Engine long-lived with correct maintenance — problem cars are almost always those with missed oil changes.
V8 BiTurbo Open-Top — the M278 at Its Acoustic Best
In the convertible the M278 loses its insulation and reveals what it contains acoustically. Open roof, deep BiTurbo rumble, 408 hp rear-wheel drive — a combination that does not exist elsewhere in the E-Class range. Not an aggressive AMG sound, but a full, composed V8 note that is at its finest at 80 km/h on a country road. The soft-top opens quickly, and the wind deflector keeps turbulence in check. The most honest E500 — because you can finally hear the engine.
Engine Weaknesses 9
All M278 built before Feb. 2013 are affected by prematurely wearing chain tensioners. Mercedes responded with a goodwill campaign: new tensioners plus a check valve in the cylinder head.
Symptoms: Metallic rattle on cold start (2–5 seconds), later also rattling when warm and on hot restart
No M278 with over 120,000 km known without cylinder bore damage. Silitec coating is sensitive to knock. Full rebuild approximately €14,000–18,000, replacement engine approximately €20,500.
Symptoms: Increased oil consumption (1–1.6 L/1,000 km), engine knock, rough idle, brass swarf in oil
The M278 is the best-known example of Mercedes' oil migration problem. Oil seeps from the camshaft adjuster solenoid capillary-style through the entire engine wiring harness to the ECU. Costs up to €11,000 if ECU and harness both need replacing.
Symptoms: Cold-start rattle, fault codes P0010/P0011 camshaft adjuster, oil traces on connectors, sporadic engine misfires, complete ECU failure
CGI direct injectors carbon up from 120,000 km and dribble after shutdown. Post-drip washes the oil film from the bore — a direct precursor to bore damage.
Symptoms: Rough idle, fuel smell after shutdown, black wet spark plugs on individual cylinders, high consumption, misfire fault codes
The wastegate linkage bush wears and initially causes rattling on cold start that develops into a permanent noise.
Symptoms: Metallic rattle from the turbo area on cold start, sluggish acceleration, P0299 boost pressure fault code
The hydraulic engine mounts on the M278 V8 lose their damping fluid after around 100,000 km. The heavy V8 (>250 kg) then causes noticeable vibrations throughout the vehicle.
Symptoms: Vibrations at idle in the cabin, clunking on throttle application and lift-off, visibly collapsed engine mount
Ignition coils fail from around 100,000 km — usually one at a time, rarely all together. Misfires on individual cylinders, MIL flashes. Left untreated, fouled plugs wash the oil film from the bore.
Symptoms: Stumble at idle and part throttle, flashing engine warning light, misfire fault codes (cylinders 5 and 7 most commonly affected), occasional fuel smell
The oil separator (crankcase ventilation) wears and feeds too much oil vapour into the intake. Accelerates intake valve carbon build-up and measurably increases oil consumption.
Symptoms: Increased oil consumption, blue smoke on cold start, oil film visible in intake pipe, smoke from exhaust after extended parking
As a pure direct-injection engine, the M278 builds up carbon deposits on the intake valves. Walnut blasting every 60,000 km is recommended.
Symptoms: Rough idle, slight power reduction, occasional misfires when cold
Vehicle Weaknesses 14
Rear subframe rusts from the inside out. Faulty factory sealant allows water ingress. Flagged as safety-critical at MOT.
W212 steel rear subframe with powder coating cracks over time and allows moisture in. Rusts from the inside. Mercedes replaces as a goodwill gesture. Safety-critical.
Brake lines above the rear axle corrode through after 8–10 years. Brake fluid loss leads to brake failure. MOT refusal.
Rear axle corrodes through with age; suspension mounting points are flagged at MOT. Goodwill repairs possible but time-limited.
Brake lines corrode at two to twelve times the rate of comparable vehicles according to MOT data.
The rear axle is prone to severe rust-through from the inside at the weld seams of the subframe. The problem goes unnoticed for a long time. Mercedes granted goodwill replacements in some cases.
Worn joints and strut rod ends on the front axle are a recurring problem. Classic wear pattern at higher mileages.
Drain holes in the sills clog up; water collects and promotes rust from the inside.
Fabric soft-top develops cracks and leaks over the years. Moisture can damage control units.
Worn ball joints and strut top mounts on the front axle are a recurring problem. Individual owners reported multiple repairs.
The soft top tends to develop cracks in the fabric after about 10 years. Ignored cracks lead to water ingress, mould growth and control unit damage.
The drain channels in the sills clog regularly, causing water accumulation and corrosion in the sill area. Control units in the floor area can become damp.
Knocking and rattling from the front axle on uneven road surfaces. Causes: worn ball joints, anti-roll bar bushings.
The parking brake is regularly flagged at MOT. Corrosion from infrequent use causes it to seize or fail.