Randombloke

Check the brakes aren't binding. Even the slightest bind seems to affect the 2.2 HDi.

Have a look at the mass air flow sensor, check it's not dirty or broken. It's a hot wire type of flow sensor. Don't touch it to clean it but maybe clean it with a carb cleaner spray. Make 100% sure there are no air leaks on the intake side of the engine. See if there is a puddle of oil at the bottom of the intercooler where the hose is attached - sometimes this can reduce performance if the intercooler has a lot of oil in it - might require a clean out. Make sure that you have full accelerator travel - get someone to floor the pedal for you whilst you check that there is no travel left in the throttle position sensor at the other end. Remove all after market floor mats in the driver's foot well and see if that changes things.

When it breaks it usually leads to an "Anti Pollution" fault warning.

Wiring diagram and a voltmeter work round the connections.

The thermostat/adjustment is on the seat base next to the door, towards the front of the seat, in front of the electric controls for the seat if you have them. You can set three levels of seat heating or off, if it's fitted.

Hazard relay loose in socket or completely Donald Ducked?

Find another dealer or indy and get the fault codes read, and given to you as the actual codes themselves.

Citroen dealer, search forum for part number details...

I'm pretty sure the German reference in the ads is a UK only thing, I think if it was done in France then the factory in Rennes would be torched.... :) Get ready for Alfa Romeo levels of depreciation on Mk III C5s. AFAICT it's a smaller car so I'd hopefully end up with a late Mk II when my Mk I estate needs to be scrapped. I predict that most MkIIs will eventually end up with the DPF removed from the engine management system (by re-programming) when they are past 10 years old.

Look to see if the height corrector at the rear is stuck, it's a valve thing connected to the anti roll bar. Give it a squirt with some WD 40. Then give the rear of the car a bit of bounce as if testing shocks.

Sorry mate, you've got the spammy tw*ts again, I'd love to ban them all. Keypad, similar to 406. If it's in the centre console, I would try lifting it out and examining for frayed wires or damaged wires, if it's hinge down job under the dash it's definitely damaged wires. There is as repair kit or you can solder then use Hellerman sleeving to cover the joints. Have a look at the diesel pump or the ECU at the other end of the loom for the same problem. Unplug the keypad from the wiring and see if you can see any dry joints (soldering) where the socket is on the circuit board. My first work around would be to pair the keys to the car, if you still have the plips working. Pair both plips to the car, search for instructions on line, this allows you 60 seconds to start the car AFTER it has been opened with the plip key. Then you can forget the pad. The keypad is paired with the diesel pump AFAIK on the 406 (PSA parent company, same floor pan, electrics and engines, just no hydraulic suspension) so I don't think you can swap the pad out easily. I had to get a repair kit to fix my pad but was able to pair keys and use this as a work around. It would also be worth looking for a minor fluid spillage and maybe using some circuit board cleaner on the keypad. Be careful though.

Measure the battery voltage when the engine is not running, and when it's running. Check all the electrical connections but DO NOT disconnect the battery without following the procedure elsewhere on the forum. Lots of problems with the C5 can be caused by low battery volts, the battery may still crank fast, but low voltage can allow spikes into sensors. If the battery does not seem too healthy then replace it. 12.6 to 13.2 volts engine off, 13.6 to 14.4V engine on - this is what I get with mine. Sometimes it's lower on switch on because the electric suspension pump runs. If the battery is fine then consider the reset process outlined elsewhere on this forum. Check the connections to all the ABS sensors from the wiring loom are OK, and if not maybe give them a clean, but be careful not to break or damage any connectors. Check the ABS fuse. Coastline?

Early C5s seem to suffer from binding front brakes. I end up checking mine every year about this time, clean them up and there is usually another 4mpg to be had, or 6 mpg on long runs.

C5 annoyances specific to second hand cars The previous owner does not have the card with the confidential code. You'll need this for new keys and Citroen now charge for re-issuing it. The previous owner has only one key. Maybe consider just getting a garage key without the expensive “plip” bit on the back. The previous owner does not have the manual. You'll have to get a new one from Citroen or eBay. More annoying is the people who have bought a manual for the Mk 2 version but own a Mk 1, like the guy who sold me mine. There is no evidence of cam belt changes (c. 100k) or DPF changes/Eolys replenishment (50k, 72k). This affects mostly 2.2 HDi cars. If buying a car with about 90+K on it factor in the belt change. If buying a car with 50k, 72k or 100k on it check via RPN when the Eolys/DPF is due, and if it has been done. The rear screen is incredibly unlikely to still work. Have you got the gaffa tape, soldering iron and wire? The corrosion inspection at four and six years will probably not have been done. The sun roof sticks (intermittently) or does not work. Without the manual you will not know that pushing and holding the control upwards into the roof over rides the pinch protection and will let you shut the sun roof in an emergency if it has stuck or got out of sync with the control. The reporting valves tell you the tyres are under inflated or flat/damaged when they are fine. The car has 4 random brands and treads of tyre. The central locking will not work on one or more doors. The pinch prevention on the windows might need recalibrating, and without the manual you will not know that there is a procedure you can try yourself. The aerial has rusted on and will not unscrew with getting broken. New aerial and base needed. The headlights are wickedly expensive and worth buying acrylic covers for. Most of these are problems caused by people, and are not problems with the C5 itself. I also have a table of some other problems, PM me and I'll mail it to you.

So, You want to Flush out Your Citroen Hydraulic System? I don't know where it can be purchased in the UK, but you could ring this lot and ask them, as they fix a lot of Citroen cars, and did the flush on mine: Mid Kent Vehicle Services or try and of the bigger Citroen Hydraulic bits retailers in the UK. As for what else they might call you, try pronouncing MR2 the French way. Another car whose name was not thought out, like the Mitsubishi Pajero in Spain.

Car details? 2001->2004? 2004->2007/8? 2008->present?

I bought the CD for my 2002 C5 to update it from Citroen Auch. It cost me €22. Google it, but the site is in French.

But you must have learnt the expression "vache Espagnole"? My local Citroen indy says it's called the centre sphere. If you look at all the part numbers on all six spheres you might be able to find 2 that are the same to swap round, but I doubt it. You could try putting Hydraclean though the hydraulic system - don't leave it in for more that 1,000 miles and do the filters afterwards. This might free up the anti sink valve. Failing that, buy another sphere. ISTR that when my BX spheres got harder, it didn't affect the sinking. What made the biggest difference was the Hydraclean which ended up being used probably 3 or 4 times in the life of the car. If you do the rounds you can have one posted to you from the UK today. There's a certain irony that the cars are mostly made in Rennes, and there are loads of people in France who can fix Citroen, but that's a minor detail.

Search the forum, Coastline has already posted the solution, it was something along the lines of take the door interior off and do some WD40 action. I have the same fault intermittently and intend to do the same when the weather warms up.

I've had this problem and solved it by replacing the rear glass release switch. Pictures are here: FixingTheRearGlassReleaseButton The OP needs to sell the C5 and buy another Mondeo.

I always lock the car when I leave it to avoid this behaviour flattening the battery, which it may do if the car is on ground that is not level.

Get either an RTS manual in France or a Haynes manual from the UK and they will tell you. Seeing as you don't agree with the reply you've already had it seem you want someone to agree with you that it's the centre sphere. Take the centre sphere off. Get it tested. Job done. If it not that then it could be the anti sink valve, Xantias were fitted with this after about 94 to stop them sinking at the rear. It could also be that the hydraulic pump is tired. Some places will recharge the spheres for you, but they tend not to do this for the accumulator sphere. Maybe the accumulator sphere itself is tired? This was the cause of my BX sinking fast after switch off, but it had no anti sink. IME, spares can be very cheap in France. You simply need to know where to look.

Don't Xantias (almost all of them except the earliest) have an anti sink valve? Is the suspension at the rear getting hard? If not it may be the valve. You should be able to get the spheres tested by a Citroen garage.

Coil Spring? What coil spring? It's a 2001 C5 - they all have spheres........

No balance weights gone missing? Otherwise, I'm afraid that Coastline's suggestion looks very likely.