Citroën C6

The DW12 uses two turbos in a parallel sequential arrangement. The small turbo works alone up to 1,400 rpm; both operate from 2,500 rpm. Seizure or bearing wear in one turbo causes uncontrolled boost pressure. Complex and expensive to repair.

Symptoms: Power loss, whistling/rattling noises, smoke, fault code.

The 2.2 HDi with EOLYS-based FAP is considered particularly susceptible to DPF problems. Lack of motorway driving leads to blockage. Regeneration failure increases oil dilution. Some mechanics fundamentally advise against this engine for short-trip drivers.

Symptoms: FAP warning light, power loss, limp mode, strong fuel smell in oil.

Under high mileage and thermal stress, DW12 cylinder heads can develop cracks. Known among mechanics as a problematic engine. In isolated cases, a complete engine swap from 2.2 to 2.0 HDi has been performed.

Symptoms: Coolant loss, mayonnaise in oil, overheating, white exhaust smoke.

The turbocharger on the DW12 2.2 HDi suffers from oil sludge and contamination that restricts the turbo's oil supply. Shaft play, whistling noises, and eventually bearing seizure are the result. Oil must be changed regularly.

Symptoms: Whistling turbo noise, blue smoke on acceleration, increased oil consumption above 0.5 L/1000 km, power loss. Turbo no longer spins up freely under load.

The crankshaft torsional damper wears at higher mileages. The inner and outer rings begin to slip, leading to rough running, knocking noises, and accessory belt drive problems. Known with heavy use.

Symptoms: Knocking/squealing at idle, belt noise, slightly rough engine running.

The EGR cooler on the DW12 2.2 HDi develops cracks and drips coolant onto hot exhaust parts where it evaporates. No visible external coolant loss. Risk of gradual overheating; coolant must be topped up regularly.

Symptoms: Gradual coolant loss with no visible external leaks, whitish steam from exhaust, cooling system requires frequent topping up, coolant warning light.

The Hydractive 3+ suspension on the C6 I fails from around 60,000–80,000 km with leaking spheres and cylinders. The car sinks on one or more corners and the ride becomes hard. Repair is labour-intensive and expensive; Citroën has discontinued spare parts.

The BSI and BSM central control units on the C6 I are no longer available from Citroën as spare parts. A fault in these ECUs can permanently immobilise the vehicle. Electronic problems with fault cascades (ABS, ESP, parking brake) appear from 50,000 km.

The automatic gearbox in the C6 I wears out its solenoid valves in the hydraulic block from 80,000–100,000 km. Jerky shifts and gearbox failures follow. A gearbox oil change with special ATF every 60,000 km is mandatory but is frequently ignored by previous owners.

The C6 I shows problems with brake lines at higher mileages (80,000–100,000 km) that can lead to pressure loss. Brake discs and pads wear above average, especially the front discs from 40,000–60,000 km.

The C6 I shows corrosion at wheel arch inner edges and on the underfloor, especially on vehicles without regular underbody sealing. Older examples from 2005–2007 are more severely affected.