C5 X7 late 2009...uncertainty about the suspension problem

[rmunns]

You must all be getting fed up with my questions and antics in trying to fix my suspension problems. To briefly recap....Car failed CT (MoT in France) because suspension is judged too supple. The tester showed me his test method - i.e. just pushing down in each corner in turn. Yes, car does take 2 or 3 bounces to stop on each corner. I suppose it ought to be just one bounce, ending slowly. Anyway, he reckoned I need 4 corner spheres.

The car has, I think, gradually become more wallowy to drive and is not as sharp as it was in corners. I've owned car 4 years, starting at 196k km, now at 223k km (122k miles to 140k miles).

But to me it just seems more likely that the problem is central.....so it affects the whole system. Like the centre sphere at front / 2 centre spheres at the rear. &/or the fluid.

I have had advice from two garages - one says replace all 4 corners and replace fluid, the other says replace all 3 centre spheres and replace fluid. And a friend insists that these spheres go hard when they are worn out, so that would not mean a soft ride. Oneof the garages said that if one sphere is failing then it would affect the ride (but then, why not replace just one sphere?).

So I am unsure what to do. I did start to change the fluid myself, but got in a frightening mess and abandoned doing that. The final general moan is of course money. These quotes are at €800 and €600 and for me this is a lot to pay for what may well turn out to be an unnecessary 'fix'.

Please; opinions. The base question is what is the likely cause of a walllowy ride in a C5 with hydractive III ?

[xantia_v6]

I would not recommend spending any money on repairs until you can identify a specific fault.

I think that your initial CT tester was ignorant of the correct operation of the suspension. Is there a testers manual for CT tests explaining how suspension should be tested and what are the criteria for failure?

If you have no other source of diagnosis, it might be worth taking it to a Citroen dealer for evaluation (and perhaps a CT test).

[GiveMeABreak]

Agree Roger ^ I can't see how the ride gets softer with the spheres hardened with no gas - doesn't work like that. On the X7, the 3 centre spheres provide the extra cushioning when energised - giving you normal comfort mode - when the car want to firm up the ride, it isolates the centre spheres leaving only the outer 4 corner spheres. So the ride is noticeably firmer into the corners etc. So if your spheres where not operating properly or there was no gas (unlikely) then the ride would be harder, not more supple.

You should be able to easily test if the centre spheres are cutting in or not: Go for a spin on normal suspension settings and throw the car round a few corners and take note of the roll. Now engage SPORT setting and do the same again - you should easily be able to see the difference in the firmer ride and reduced body roll.

If there is no discernible difference, then it is possible wither the front or rear centre spheres are not cutting off when commanded, resulting in a more 'wallowy' mode all the time.

Diagbox should be able to tell you if the centre spheres are cutting in or not through actuator tests. This and a general diagnostic of all the suspension actuators really should be done first, or yes, you could be replacing parts unnecessarily.

[rmunns]

Thanks again for your kind replies.

Marc, I did throw the car about a bit round sharp corners, but really couldn't tell any difference when in or out of 'Sport' setting.

I went to the main dealer in Bergerac to book in for a 'diagnostique'. So I guess that's €85 spent, but it should at least tell me for certain what is wrong.

I'll come back on here and say what they reckon should be done.

[white exec]

Agree with Marc - Sounds if the car is stuck in Soft mode, with the centre spheres somehow permanently in circuit. Confirm that lack of gas (sphere failure) would result in firm ride, not soft. Another cause could be incorrect corner spheres (with too little damping), but presume unlikely.

[rmunns]

Again. Sorry for delay in replying, now things are sorted. After 3 weeks of umming and arrhing I took the car to a second MoT (CT in France) station and it passed! So no need to do the work. There is a need, however, to find my wallowy ride reason.

[xantia_v6]

Congratulations on the pass!

Have the characteristics of the suspension changed, or are you now being more fussy?

Did you get the diagnostique at the dealer?

[rmunns]

Oh, you mean the 'diagnostic' ('diagnostique') at the local main Citroen dealer? They said 'Bonjour, avez-vous le CT papier svp?' (Have you got the MoT paperwork, please?). 'Reviens une heure'. (Come back in an hour). I did. The paperwork summarising the 'diagnostic' was timed and dated at 11 minutes after I left the car. They had done nothing other than look at the CT paperwork, which said (translating) 4 spheres faulty and issued me with an estimate for the work. No computer connecting. No road test. Naturally I told them what I thought.... just a return gallic shrug.

I am sure the car is more ship-like than it was when I first got it (2015). But now, with a new CT (lasts 2 years) I have time to get it sorted. I hope.

[white exec]

What happens if you do a bounce test?

All doors etc shut
Engine running
Car risen to normal height
Push down firmly on rear end repeatedly
- does it feel springy?
- how far can you push down?
Do the same at the front
- same questions

Turn engine off, all doors etc closed
After 30 secs or so, can you hear an audible loud click from each end of the car (the front and rear suspension electrovalves switching off)?
Press down firmly on each end of the car again
- does it feel different?
- how far can you push down?

This is a test of the car being able to achieve (i) soft mode, (ii) firm mode.

[rmunns]

Thanks, Chris. Only just saw this--------------I'll try tomorrow.

[GiveMeABreak]

Not sure that will work with an X7 Chris.... The best way to check the electrovalves cutting in or out is with Diagbox - there are actuator tests to do this because the system won't cut these in or out unless the driving conditions dictate.

[white exec]

OK, will be guided by you on that Mark.
Does C5III not migrate from firm (when left parked) to soft (stationary, engine running) like its predecessors?

[GiveMeABreak]

The Hydractive 3+ Suspension application has 6 input information monitoring modules:

• "heights monitoring" module
• "steering wheel angle monitoring" module
• "steering wheel speed monitoring" module
• "engine torque monitoring" module
• "deceleration monitoring" module
• "sportiness coefficient calculation" module

In the case of the 'heights monitoring module':

The monitoring of the wheel travel information is in relation to the vehicle speed.

When the travel values exceed the threshold of the map selected ("soft" or "sport"), the "firm" suspension stiffness pattern is selected.

The wheel travel values can be placed in 3 categories:

• Normal road
• Driving over obstacles ("wheel knocks")
• Road in poor condition

The suspension switches to the "firm" pattern when the travel of the wheels exceeds a threshold determined in relation to the average position.

The suspension switches back to the "soft" stiffness pattern when the minimum thresholds are reached after a timed period:

• Timed period of approximately 0,8 second for the "soft" suspension stiffness pattern
• Timed period of approximately 1,6 seconds for the "sport" suspension stiffness pattern

So with regard to the wheel height monitoring which would be the 'bounce' test, the car won't be moving, so the firm setting will not be engaged.

The vehicle is always in soft mode when stationary as this is the only mode that will allow the height to be raised and lowered manually.

[xantia_v6]

The vehicle is always in soft mode when stationary as this is the only mode that will allow the height to be raised and lowered manually.

Is that true when the vehicle is parked and switched off?

[white exec]

That was my question, too... Whether soft and active when stationary, but firm after engine has been switched off (and after the H3 has shut down) - which should allow a bounce test.