Mercedes-Benz ML 500
Naturally aspirated V8 in three displacements from 4.3 to 5.5 litres — old-school character with no turbo lag. Linear power delivery, deep rumble from 2,000 rpm building to a hoarse roar above 5,000. Peak torque at 3,000; beyond that it thins out — yet it's silky in part-throttle and surprisingly economical. Achilles heel is the seals: rear crankshaft oil seal practically universal above 150,000 km (gearbox removal required, 600–900 EUR), valve covers and oil filter housing seep with age. All cheap parts. The one critical point: the rubber damper on the crankshaft pulley hardens with age — when it fails the pulley machines into the sump. Replace preventively every 150,000 km. Oil changes every 10,000 km with 5W-40, 16 spark plugs every 60,000–80,000 km — then 400,000 km is realistic.
ML 500 W163 — More Displacement, Same Issues Around It
292 hp V8, cylinder deactivation saves fuel on the motorway. More torque than the ML 430, barely noticeable in daily use. W163 problems remain: rust at sills and wheel arches, headlight condensation, torque converter on kickdown abuse. Engine lasts forever; body and electronics define the lifespan.
Engine Weaknesses 10
The rubber damper in the crankshaft pulley hardens with age and can eat into the sump — catastrophic consequential damage. Preventive replacement every 150,000 km strongly recommended.
Symptoms: Unusual vibrations at idle, in worst case metallic scraping from below. Often no prior warning — sudden failure.
The rear crankshaft seal is leaking on virtually all M113 engines above 150,000 km. Gearbox removal required — 600–900 EUR workshop costs. If oil creeps into the torque converter it becomes expensive.
Symptoms: Oil drops or oil film visible at the engine-gearbox interface, oil loss without any other apparent leak on the engine.
Engine mounts can fail before 100,000 km. Practical test: finger between the stabiliser bar and front sump — no clearance means the mount is dead. Not visually checkable without removal.
Symptoms: Vibrations in interior especially at idle, dull rumbling on acceleration, in worst case contact between engine and bodywork.
Faulty thermostat leads to permanently low engine temperature (increased wear) or overheating in traffic jams. Part costs 24 EUR — swap it immediately on suspicion, do not wait.
Symptoms: Temperature gauge permanently below mid-point (thermostat opens too early) or engine overheats in traffic (thermostat stuck closed).
The front crankshaft seal hardens with age. More accessible than the rear seal, but the pulley bolt is a single-use part. Oil on the drive belt damages it additionally.
Symptoms: Oil film on underside of belt drive, oil visible on drive belt.
Both valve cover gaskets harden with age and allow oil through. Cheap parts (18 EUR each), but caution: aluminium bolts on the valve cover — no over-torque or the threads strip.
Symptoms: Oil smell in engine bay, visible oil film on lower valve cover edge, smoke when oil drips onto exhaust manifold.
PCV hoses become brittle and crack. Leads to pressure increase in the crankcase, elevated oil consumption and false air ingestion. All hoses together under 31 EUR — worth replacing as a set.
Symptoms: Elevated oil consumption without visible leak, white smoke from exhaust, idle fluctuations from false air.
O-ring seals on the oil filter housing and oil cooler connection harden and seep oil. Classic ageing, cheap to fix if caught early — all three seals under 30 EUR.
Symptoms: Oil film around the oil filter area, drips under the vehicle at the front of the engine.
The bolts on the intake manifold switchover loosen. They cannot fall out but cause noise and functional disturbance. Recommendation: remove intake tract, clean, secure bolts with Loctite.
Symptoms: Clattering or rattling from the intake area, irregular throttle response, slight power drop at certain rpm.
The 16 original injectors (black) wear at high mileage. Mercedes introduced revised blue injectors. O-ring seals on the injectors can leak and allow fuel into the oil.
Symptoms: Elevated fuel consumption, idle fluctuations, fuel smell on dipstick from leaking O-rings.
Vehicle Weaknesses 7
The US-built W163 received insufficient corrosion protection from the factory. Boot lid, sills, wheel arches and bonnet are particularly susceptible.
The wiring harness at the ABS hydraulic block chafes against the wheel arch liner and causes ABS and ETS failures. A known design fault.
Brake lines are known to corrode through. Complete replacement requires removal of the rear axle, driveshaft and fuel tank. A safety-critical problem.
The automatic transmission suffers premature torque converter wear, particularly on the ML 400 CDI and with frequent trailer use.
The transfer case chain stretches from around 100,000 km and can jump. Noises on pull-away are an early warning. In the worst case, total drivetrain failure.
Ladder frame rusts heavily, particularly at the rear and at longitudinal member sections. Suspension mounting points can be so weakened by corrosion that the vehicle's roadworthiness is at risk.
Cables in the tailgate transition break through constant opening and closing. Rear screen wiper, third brake light and number plate lighting are affected.