Peugeot 508
Updated THP with 165 hp and improved timing chain. Significantly more reliable than predecessor EP6DT.
New 508 with 181 hp — composed
The new 508 R8 with 181 hp from the developed 1.6 turbo feels pleasantly potent. The auto pairs well with the engine, long journeys are effortless. A mature drivetrain for the elegant mid-size estate.
Engine Weaknesses 6
The EP6CDTX has a reinforced chain and revised tensioner (white guide rails instead of brown). Nevertheless, chain stretch occurs from around 100,000 km — less frequently than on EP6DT/DTS, but still relevant.
Symptoms: Slight rattle on cold start until oil pressure builds, valve timing fault in OBD, rough idle after warm restart
The EP6CDTX also uses direct injection exclusively. Oil mist and EGR gases cause stubborn carbon deposits on the intake valves. Cleaning every 60,000–80,000 km is recommended.
Symptoms: Gradual power loss, increased fuel consumption, hesitation at low revs, occasional misfires
The high-pressure pump of the EP6CDTX gradually loses its internal hydraulic oil over time. It wears faster with frequent short-trip use and in hot climates. Fault code P0087 is typical.
Symptoms: Power loss under load, engine stumbling at high revs, starting problems, MIL with fuel pressure fault
The electric water pump with integrated thermostat is the same design as the EP6DT/DTS and remains a wear item. A leak or pump failure creates overheating risk.
Symptoms: Coolant temperature rises, coolant loss without visible external leak, overheating warning, heater goes cold
THP165/200 high-pressure pumps lose oil pressure through worn seals. Intermittent power drops at 1,800–3,500 rpm; fuel pressure drops below 40 bar. Always replace the seal kit during repair.
Symptoms: Sporadic power drops under acceleration, unburnt fuel smell, engine warning light
The solenoid valve for variable cam timing fails on THP engines, causing power loss and fault codes. More common on pre-2014 models.
Symptoms: Rough idle, engine warning light, power loss at mid-range revs
Vehicle Weaknesses 9
The 508 PHEV (plug-in hybrid) was subject to recalls due to potential fire risk from faulty high-voltage battery components. Defective battery packs can catch fire when overheating or short-circuiting.
From around 100,000–150,000 km front and rear axles on the 508 II show wear on bearings and bushes. Wishbones and anti-roll bar drop links are the most common wear items.
On the 508 R8 owners report play in the steering column and creaking/clicking when turning. Defective steering joints or worn column bearings are typical causes.
The EAT8 automatic gearbox shows too-late or poorly adapted gear changes on some examples. Regular gearbox oil changes per the service schedule reduce the problem considerably.
The touchscreen infotainment regularly shows software faults: inaccurate GPS position, DAB radio drop-outs, Bluetooth connection issues and sporadic screen blackouts.
Defective parking sensors and failed seat heating are among the most common complaints on the 508 II. Moisture ingress into PDC sensors is a typical cause.
The optional infrared night vision camera develops faults after a while. Calibration loss or camera error requires a workshop visit for recalibration.
The leather covering on the steering wheel of the 508 II delaminates on the underside after 30,000–60,000 km. The material detaches at the seams and begins to peel. Typical issue with frequent UV exposure or sweaty hands.
Below 5°C the automatic climate control stops dehumidifying and windows mist up. A BSI software update temporarily resolves the issue. Cut-outs under strong sunlight are also known.
