The last of the great French executive saloons, offering remarkable ride comfort from its Hydractive III+ hydropneumatic suspension. Only 23,384 C6s were ever built, making it rare and specialist knowledge essential. The 3.0 HDi V6 is more refined and powerful than the earlier 2.7, but maintenance costs are high due to complex systems. Key concerns: hydropneumatic suspension pump and sphere failures, EGR valve problems (15 hours labor to replace), front suspension ball joints and FRIP joints becoming service items, and the BiTurbo system requiring premium fuel. PSA discontinued hydropneumatic suspension production in 2017, making some parts increasingly scarce. A specialist Citroën garage with Lexia/Diagbox diagnostic equipment is essential.
Carbon brush wear causes pump motor failure, car drops to bump stops · more· less
The BHI (Bloc Hydro-électronique Intégré) pressurizes LDS fluid to 150-180 bar for the suspension and power steering. Carbon dust from worn brushes can create a conductive paste that shorts the motor windings. Symptoms include blown 40-50A fuse, suspension warning lights, or car sitting unevenly. Brush replacement kits cost €25-40 for DIY repair. Remanufactured units from specialists (BBA-Reman, Actronics) cost €500-800 exchange. New OEM pumps are increasingly scarce since PSA discontinued hydropneumatic production in 2017. C6 units are mechanically identical to C5 units but require Diagbox recoding if not from the same spec vehicle.
EGR valve failure€1,400 - €1,800
EGR valves clog rapidly, transverse V6 makes replacement extremely labor-intensive · more· less
The transversely-mounted V6 has very poor access to the EGR valves. Citroën dealers quote approximately €1,550 including 15 hours of labor. Symptoms include reduced power, engine warning lights, and increased emissions. One long-term owner reported replacing EGR valves twice in 10 years. Alternative: ECU remapping to disable EGR function is common (€300-500), often combined with performance tuning. Using premium diesel (Shell V-Power, BP Ultimate) significantly reduces carbon buildup. Wynns EGR3 spray treatment (€15-20) can help clean in situ as preventive maintenance.
Front suspension ball joints / FRIP joints€400 - €1,200
Front suspension not designed for C6's weight, joints become service items · more· less
Long-term owners report that the front suspension was not adequately designed for the C6's weight. Ball joints and FRIP (Front Right Inner Pivot) joints wear prematurely and should be considered service items. One owner spent £3,000 in three months on front suspension work including drop-links, bearings, lower wishbones, stub-axles, and two complete struts. Parts cost €17-208 per component. Symptoms include rattling, chattering over bumps, uneven tire wear, and twitchy cornering. Budget for front suspension work every 40,000-60,000 km.
Turbo vacuum valve failure€200 - €400
BiTurbo system uses 4 electric vacuum valves that commonly fail · more· less
Sometimes one of the two turbos will not kick in. If the first turbo fails to spool, the second won't engage either because the engine can't reach the required revs. If only the second turbo fails, you'll notice power dropping off around 2,600 rpm. In most cases, the problem is one of the 4 electric vacuum valves controlling the turbos, not the turbos themselves. Each valve costs under €50. Recommended fix: replace all 4 valves when one fails (€200 parts + labor). Full turbo replacement if actually needed costs €950-2,500.
DPF (particulate filter) blockage€150 - €2,500
Short trips prevent regeneration, Eolys additive system adds complexity · more· less
The Citroën Eolys additive system lowers regeneration temperature to 450°C, but short urban trips can still prevent proper regeneration. Symptoms include DPF warning light and limp mode. Professional cleaning costs €130-200. Forced regeneration using Lexia/Diagbox costs €90 but places high stress on components. If the DPF is terminally blocked, replacement costs €1,500-2,500 including fitting. Prevention: regular 30+ minute motorway drives at constant speed. The additive tank needs refilling every 80,000-120,000 km (€80-150). One long-term owner replaced particulate filters three times.
Hydraulic suspension strut failure€1,000 - €1,500
Struts can fail from pothole damage or age, expensive to replace · more· less
Cars that have hit potholes or been in accidents may display suspension issues due to strut damage. A complete replacement strut including fitting costs over €1,000 per corner. Suspension sphere replacement (if separate from strut) is needed every 4-5 years or 60,000-100,000 km, though Citroën claims "lifetime" for newer slimline spheres. Signs of worn spheres: bouncy, hard ride. Sphere cost: €37-140 each, with 6 needed for full replacement (approximately €260 total parts).
Hydraulic power steering pipe failure€600 - €1,200
High-pressure hydraulic pipes perish with age, some parts now unavailable · more· less
The C6 uses shared hydraulic fluid (LDS) for both suspension and power steering. High-pressure pipes can perish and leak over time. One long-term owner reported a hydraulic power steering pipe repair requiring 6 hours of labor. Some power steering and hydraulic pipes are no longer available from Citroën, making sourcing from breakers or specialist suppliers necessary. Pipe costs approximately €110-130 plus extensive labor. Symptoms: power steering fluid leaks, heavy steering, LDS fluid puddles.
AM6 automatic gearbox issues€500 - €3,000
Aisin 6-speed auto generally reliable but has known torque converter issues · more· less
The AM6 (Aisin Warner) 6-speed automatic is generally reliable, but Citroën's "sealed for life" oil claim is optimistic. Known issues include difficulty shifting from 2nd to 3rd gear (high revs), trouble engaging reverse, and torque converter problems causing stalling when shifting from P to D/R. Torque converter regeneration costs approximately €500-800. Full gearbox replacement if needed: €2,500-3,000. Preventive maintenance: change gearbox oil every 100,000-120,000 km despite "sealed for life" claim.
Electrical gremlins / sensor failures€200 - €800
Complex electronics prone to intermittent faults, weak battery causes cascade failures · more· less
The C6 is extremely sensitive electronically. A weak or failing battery can trigger numerous false warning lights and system errors. One long-term owner replaced four ABS sensors over time (causing handbrake, SatNav, and ABS malfunctions). The fore-aft leveling sensor failure caused the front to jack up while the rear sat on bump stops. Navigation system freezing, black screens, and GPS signal loss are common. Instrument cluster repairs available from specialists (STS Tech). Always maintain a good quality battery and check earth/ground connections. Diagbox/Lexia diagnostics essential for proper fault finding.
Complex systems require specialist knowledge and budget
The C6 is a magnificent touring car when working correctly, but its hydropneumatic suspension, BiTurbo diesel, and sophisticated electronics demand specialist maintenance. Long-term owners report spending approximately €1,200 annually on upkeep. Most problems occur between 60,000-100,000 km, often after warranty expiration. With fewer than 270 C6s still registered in the UK, finding experienced specialists is becoming more challenging. Not a car for the faint-hearted or those without access to a Citroën specialist with proper diagnostic equipment.
Pre-Purchase Inspection Checklist
General checks
Service history
Complete service records essential. Verify timing belt changes at 150,000 km / 10 years. Oil changes every 15,000 km with 5W-30 or 5W-40 fully synthetic.
Cold start
Must start engine completely cold. Listen for turbo whine, unusual rattles, or rough idle.
Body condition
Check for rust, accident damage, paint mismatch. Inspect wheel arches and sills.
Test drive
Minimum 1 hour including motorway and congested town driving to stress all systems.
Specific for this vehicle
Suspension height and leveling
Start the car and watch suspension rise to normal height (takes a few seconds). Check all four corners sit level. Uneven ride height indicates sphere, strut, or sensor problems.
Suspension mode operation
Test all suspension modes (Comfort, Normal, Sport). Each should produce noticeably different ride firmness. If modes feel identical, system is not functioning correctly.
Listen for suspension pump cycling
The BHI pump should not run continuously. Constant cycling indicates hydraulic leak or worn pump. Listen for pump running with engine on but car stationary.
Check for LDS fluid leaks
Inspect under the car for orange LDS hydraulic fluid. Check around struts, pump, and steering components. Any leaks are expensive to fix.
Front suspension rattles and play
Drive over speed bumps. Listen for rattling or chattering. Grab each front wheel at 12 and 6 o'clock positions and check for play indicating worn ball joints.
BiTurbo boost operation
Accelerate firmly through the rev range. First turbo should spool early, second should come in around 2,600 rpm with noticeable push. Power dropping off at 2,600 rpm indicates vacuum valve failure.
Gearbox operation when warm
After extended driving, check for harsh shifts particularly 2nd to 3rd. Test reverse engagement. Any hesitation or clunking needs investigation.
Dashboard warning lights
Many C6s on the market have intermittent engine lights. Request diagnostic scan with Lexia/Diagbox to read stored fault codes. Generic OBD2 scanners miss Citroën-specific faults.
Battery health
Have the battery tested. Weak batteries cause cascade electrical failures on the C6. Replace if marginal.
Various electrical/suspension TSBsCheck with dealer
Contact Citroën with the VIN to verify all recalls and TSBs have been completed. The C6owners.org website maintains a database of known TSBs and technical tips. Log in to MyCitroën to receive notifications about any future campaigns.
Warranty Status
Factory warranty (2 years unlimited km)Expired on all C6s
Citroën Extended Warranty eligibilityUnder 10 years / 100,000 miles
Third-party warranty (Warrantywise, etc.)Available but check exclusions
All C6s are now well outside their original factory warranty. Extended warranties are theoretically available for vehicles under 10 years old with less than 100,000 miles, but most C6s exceed these limits. Third-party warranties from providers like Warrantywise are available but carefully check exclusions for hydropneumatic suspension, turbos, and electronics, as these are the most likely failure points.
This report is for informational purposes only and does not constitute professional advice. Estimates may be inaccurate. Always have a qualified specialist inspect the vehicle before purchase. We accept no liability for decisions made based on this information.