C5 hard suspension
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  1. #1
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    Default C5 hard suspension

    Trying to help a "mature aged" friend with his C5. His car, C5 2002 16v, has quite firm suspension compared to my C5 (2001 HDi). His car has the "sport" mode switch option, mind does not. I was wondering if the sport mode might be stuck on?
    There feels no difference when the sport mode is on - as indicated by the switch being lit after pressing - or off. Should there be a difference by feel when pressing down on the front and driving over bumps?
    Is there a way of checking if the sport mode is in fact turning off?

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    Thanks
    Michael

  2. #2
    1000+ Posts Ken W's Avatar
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    Michael,

    No responses??? I don't have experience with these exact models, but I can try to use my intuition from earlier and later similar systems. It sounds like your C5 HDI does not have a hydractive suspension option but your friends C5 16V petrol? does if it has a sport suspension button. The hydractive system has two modes, soft and firm. The car will always start out in soft mode but will switch to firm when it detects from a range of inputs that cornering forces or road surface changes are getting large. All the sport button does is make it change from soft to firm happen a bit sooner. There are electrovalves front and back that when active connect the soft front and rear centre spheres to the firmer spheres mounted on each wheel suspension unit. When the electrovavles are active and the hydraulic circuit is connected, this makes the ride softer than it is when just using the firmer suspension spheres, and, by allowing fluid flow from side to side, anti-roll forces are only generated by the anti-roll bar. In firm mode, the suspension unit spheres are isolated from the opposite side and add to the anti-rolll bar forces as well as providing much firmer springing.

    When you unlock or open the door on a hydractive Xantia or C5, you can hear the hum (500Hz) of holding square voltage wave that holds the electrovalves open from front and the rear of the car. If you close the doors, it will softly hum for about 30 seconds and then you will hear a click as the eletrovalves close. When you can hear the hum, the suspension should be soft and when it is absent it should be hard. I say 'should' because I know that some electrovalves can get lazy and on Xantias in particular will not work properly unless there is full running hydraulic pressure. You should be able to use the corner bounce test to tell the difference between no hum firm suspension and humming soft suspension if all the spheres and electrovalves are behaving normally.

    All C5s have double membrane spheres that have a life of 10+ years before losing any gas. Both of these cars are now over that age so some spheres could be blown. It is not worth getting these regassed as they will just leak again, they need to be replaced. A good place to start checking out your friends car would be to get the six spheres checked to see if any have blown yet. I am not sure if you need a Lexia to depressurise these so you can then unscrew the spheres and get them tested - someone else may know.

    All that said, I have a non-hydractive Xantia wagon and a hydractive Activa. To me the ride on the wagon appears softer than does the Activa ride in soft mode. I don't really understand why this is the case but I have noticed before that older spheres seem to get softer for some reason.

    I hope this is correct and helps you a bit. There are lots of other threads on here that you could find if you searched for Hydractive. There is also a very good pdf book you can download from the 'BX do it yourself' website (use Google search) which describes all the generations of hydraulic citroen suspension in excellent detail and with good diagrams.

    Cheers,

    Ken W

  3. #3
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    Default

    I have no idea how a C5 hydractive relates to an XM hydractive, but this is about being stuck in hard mode- http://cx.podolsk.ru/xm/garage/Hydra...lt_finding.doc (MS doc format)

  4. #4
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    Quote Originally Posted by michael16v View Post
    Trying to help a "mature aged" friend with his C5. His car, C5 2002 16v, has quite firm suspension compared to my C5 (2001 HDi). His car has the "sport" mode switch option, mind does not. I was wondering if the sport mode might be stuck on?
    There feels no difference when the sport mode is on - as indicated by the switch being lit after pressing - or off. Should there be a difference by feel when pressing down on the front and driving over bumps?
    Is there a way of checking if the sport mode is in fact turning off?

    Thanks
    Michael
    Hi Michael,
    The quick answer is connect it to a Lexia and see what it says. It will be able to turn it on and off Sport mode so you can see if the light is indicating correctly.
    Anyone out there nearby with a Lexia.
    Cheers jaahn

  5. #5
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    Default

    Thanks to all, your explanations and ideas help. I doubt that ALL spheres are flat, as there is more movement in the rear - as in virtually none in the front - so front spheres flat is an option.
    There is no "500hz" sound when opening the doors, or at any other time, that I heard. I was not listening for it so will have to listen next time.
    I guess that a fault would be recorded if one was detected, as suggested, so a code read out is a good idea. Would there be a "fault warning" somewhere on the dash?
    Thanks again, and I will look into it further with more knowledge now.
    Cheers
    Michael

  6. #6
    1000+ Posts Ken W's Avatar
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    Michael,

    It is quite a soft note (its pitch is to high to call it a hum) but you should be able to pick it up with the bonnet open if it is there. The C5 Haynes manual has instructions for depressurizing the system. They recommend doing it on a hoist or over a pit so the bleed valves on the centre firmness regulators can be can be easily bled before trying to undo those spheres. For the corner spheres, apparently its a case of starting the engine and then putting the height control into the low position and waiting. I always wait until you can joggle the rear spheres around a bit showing there is no pressure left on the rear suspension cylinders. When the pressure is gone, once you get them moving, the spheres will unscrew easily if there is no pressure behind them but will be tight if there is still pressure there.

    Cheers,

    Ken W

  7. #7
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    I don't know what era this applies to but there are different levels of sphere "comfort" as well.

    For some years Aussie cars were fitted with the harder spheres - someone did a group buy several years back for "comfort" spheres which were normally fitted on one end only, if I recall correctly.

    Where have all these sphere experts gone?? ;-)

    All the best

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