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Suspension, ride height, pitching etc.
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diyjoke   
Thu Apr 04 2013, 01:59pm
Joined: Jan 27 2011
Member No: #354
Location: Wales
 Hi, I've got a 2.2 manual which is much simpler set up for the spheres etc. However, I still get the pitching from the front and (as I've mentioned here before) it seems 'harsh'.

I've requested Citroen look at this on 6 occasions and mostly didn't get any feedback whatsoever and wasted 18 months of the remaining warranty. Latest garage are keen to help and have agreed to part-fund replacement front corner spheres under 'good will'. Like the mechanic, I'm not convinced that it's entirely the fault of the spheres. A simple 'bounce' check leaning on the front wings and it all looks/feels ok.
Unlocking the car - nothing much happens but when I start the car the front RH pops up about 10mm - it used to pop up 22mm but the recent garage did all the calcs and reset the ride height; things improved but still it doesn't feel quite right. The LH side (front) isn't as bad, it doesn't lift as much or drop as much when turning the ignition off. It's booked in a couple of weeks hence to have the front corner spheres changed so I'll have to wait and see if there's any improvement.
This shows my ignorance on these matters but is there some way the car could 'think' it's cornering left all the time and increase hydraulic pressure to the affected wheel, thus lifting it slightly and giving the harsh(ish) ride sensation at this one point? Alternatively, (I don't pretend to understand how the frot stiffness regulator is switched in/out) but could the offending wheel/suspension unit not be getting the benefit of the additional regulator sphere (solenoid?). I've tried switching the sport mode on/off but it is difficult if not impossible to determine the difference for this one wheel - the overall difference is noticable.

Regards,
Barry

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rogerandoutman   
Thu Apr 04 2013, 04:49pm
Joined: May 10 2011
Member No: #466
Location: London
 Sounds like a collapsed sphere, most dealers are unable to diagnose the problem as it does not come up on a electronic check. Switch on the ignition and wait till the suspension is pressurised, then as you have done, a simple bounce on the front wings should show which spere has gone. The collapsed side will not travel as much, as the sphere will be full of LDS fluid and therfore solid. The good side will travel much further.
Pappnase   
Thu Apr 04 2013, 06:24pm
Joined: Sep 30 2012
Member No: #1044
Location: Bonn
 I had all my spheres replaced when I got the C6. I was always under the impression that the left side did not work as smooth as the right side. After changing the spheres the pitching almost vanished. However I still feel the ride could be smoother, in particular on the left side.

Last week I had the "pleasure" to experience quite a lot of good English speed bumps while cruising through Leics. Ours here are a bit less brutal. The front always bumped down with a loud thump. I wonder if this is normal. There are a few suspension related faults in the Lexia journal, but most are steering wheel sensor faults which I read are normal and nothing to worry about.

I have 4000 mls left until the next service, I shall try to do a few tests until then and complain while the car is in the garage.

Papp
Hattershaun   
Thu Apr 04 2013, 08:49pm
Joined: Dec 19 2010
Member No: #320
Location: Bedfordshire, UK
 You really need to have all 7 spheres removed from the car, so their pressures can be measured.
On my car I found that the front outer spheres were at 30 & 37 bar instead of 50 bar, so, somewhat below the correct spec. This was not detectable by pushing up and down on the corners of the car. If one of the diaphragms inside the sphere has failed you'll find it has zero pressure, which you should notice by bouncing the corners.
The front rigidity regulator sphere is either included or excluded from the front suspension circuit as determined by inputs (road speed, lateral movement of car's body, throttle position, throttle rate of change, steering wheel position, steering wheel rate of change, braking system pressure), going to the suspension ECU. When included in the circuit the ride becomes softer and more comfortable. When excluded the ride is stiffer. So, this sphere's effect/benefit is shared with both front wheels.
So, for the most comfortable ride the rigidity regulator sphere needs to be at the correct pressure. This sphere is located under the wheel arch liner on the driver's side of the car (Right Hand Drive).

To minimise any pitching the rear suspension spheres need to be at the correct pressure too.
The same principal applies at the rear with regard to the outer spheres and rigidity regulator spheres being included or excluded from the suspension circuit. There are two spheres mounted to the rigidity regulator in the middle of the car between the rear wheels, in addition to the rear outer spheres.

On my car I experienced a front to rear pitching, particularly with rear seat passengers or luggage in the boot. My rear spheres were only 5 bar below the correct spec, still enough to reduce the car's rear suspension capabilities, but relatively soft compared to the stiff front suspension! Thus leading to the pitching.

Now you need to find a garage that can pressure check your spheres.
drummond   
Fri Apr 05 2013, 07:01am
Joined: Sep 20 2010
Member No: #238
Location: Aldeburgh
 Míne pitches and rolls quite a lot, too, and I am having the spheres removed to check them. It has become very much worse in the last 3 months. I think that "they all do that, sir", and that this is a noticeable fault.

Can someone with engineering experience say whether one could purge and put LHM in the car, or would it go horribly wrong? (Remembering the LHS2/LHM improvement!)

Talking of repressurising, how did it go, Shaun?
gmerry   
Fri Apr 05 2013, 08:44am
Joined: Dec 11 2009
Member No: #21
Location: Scotland
 Drummond, I would certainly reconsider changing to LHM.

The specified LDS has more consistent/lower viscosity across lower temperatures especially and the valving/porting/pump clearances will have been designed with this fluid in mind.

Regards
G
drummond   
Fri Apr 05 2013, 10:02am
Joined: Sep 20 2010
Member No: #238
Location: Aldeburgh
 Gmerry, I would do it because the LDS is hygroscopic and LHM isn't. But, I note what you say and will consign the idea to the bits box!
Hattershaun   
Fri Apr 05 2013, 04:59pm
Joined: Dec 19 2010
Member No: #320
Location: Bedfordshire, UK
drummond wrote ...

Míne pitches and rolls quite a lot, too, and I am having the spheres removed to check them. It has become very much worse in the last 3 months. I think that "they all do that, sir", and that this is a noticeable fault.

Can someone with engineering experience say whether one could purge and put LHM in the car, or would it go horribly wrong? (Remembering the LHS2/LHM improvement!)

Talking of repressurising, how did it go, Shaun?




I fitted a set of Suplex spheres, which gave a noticeable improvement, but there were all about 5 bar below spec, and some pitching remains. Being a 'bit' fussy and wanting perfect suspension I'm keen to experience my car with all spheres at the correct pressure.
I am waiting for the re gassed spheres to come back from Plaiedes, they were due this week and will be sent to BLAutos. They were sent as part of a job lot including a DS steering rack, so I guess will be returned when the whole lot is ready.
Tjensen   
Fri Apr 05 2013, 07:36pm
Joined: Jul 17 2012
Member No: #954
Location: Bergen
 If you use some hours at internet, you will find a lot of stuff on hydraulic oils. There are lots of oils that will pass the criterias for the C6, and a lot of experimental opinions (including a shift back to old faithful LHM in a C6). But most of these ideas have not taken long time effects, extreme temperatures etc into consideration. I will stick to LHS, but miss LHM (a better solution). In Bergen, Norway, we have a lot of humidity and should change LHS more oftem, due to its hygroscopic tendencies. After 50.000 km or so I will add a "snake oil" additive for lubrication and internal rubber maintenance. This saved my XM DIRAVI steering for 4 years, stopped the leaking gaskets completely.
smihaialex   
Sun Apr 07 2013, 09:06am
Joined: Sep 18 2012
Member No: #1031
Location: Bucharest
 I knew that the old LHS used in the '50s & '60s was hygroscopic (absorbed moisture from air, just like brake fluid), and that Citroën developed LHM to overcome this, but then, I thought that LDS was a further improvement and from what I've read it was created to require even less attention (more infrequent maintenance) than LHM, so I was pretty sure that it was not hygroscopic (it did not absorb moisture from air), as this would mean that you could only use it for 3 years or so, just like brake fluid...

So either some of you gents confuse LDS for LHS, or perhaps intentionally use LHS in the C6 even though it was not intended for this, or Citroën has done the silliest of things and went back 50 years when creating LDS... :P

Which is it?!?

Yours,
Sam
travlician   
Mon Apr 08 2013, 02:07am
Joined: Jan 22 2011
Member No: #350
Location: Paradera
 LDS is hygroscopic but since the system is supposed to be closed (although new design gives another impression) it should last longer.
drummond   
Mon Apr 08 2013, 08:24am
Joined: Sep 20 2010
Member No: #238
Location: Aldeburgh
 Nah, Smihailex, they've gone back 50 years.....I'm going to Citroen Conservatoire at the end of the month, so I'll ask them (on my way out!)

Tim
gmerry   
Mon Apr 08 2013, 11:42am
Joined: Dec 11 2009
Member No: #21
Location: Scotland
 Hi Guys, before getting worried about hygroscopic nature of LDS and changing to LHM, consider the composition of LDS:-

From Total Website MSDS
3. COMPOSITION/INFORMATION ON INGREDIENTS
PREPARATION
Chemical nature : The product is made from refined mineral base oils and synthetic oils
(Polyalphaolefins).
in which the polycyclic aromatic hydrocarbons (PCA or PAH) content, measured by
IP 346, is less than 3%
Substances presenting a health hazard EC No. CAS No. Content Symbol(s) R-phrases
Alkoxylated alkylamine <0,3 % C ,N R-22, 34, 50
Alkylphosphite <0,3 % Xi ,N R-38, 41, 51/53
1-Decene dimer, hydrogenated 500-228-5 68649-11-6 <80 % Xn R-65


Ok, so there are some additives and some mineral oil, but the major percentage (say 80%)is PAO, 1- Decene, Dimer, Hydrogenated to be precise.

Chevron Philips market this as a synthetic hydraulic oil, Synfluid PAO 4cSt which will have similar base oil properties. They quote typical water content of 20ppm and solubility in water less than 1ppm.

Definitely NOT a very hygroscopic fluid by any means.

Regards
G

Note, talk about Citroen going backwards to original problems with DS hydraulics is likewise misplaced. Those LHS fluids were vegetable oil based. The PAO is like a mineral oil but much more stable and uniform in its properties being a synthetic.
drummond   
Mon Apr 08 2013, 03:48pm
Joined: Sep 20 2010
Member No: #238
Location: Aldeburgh
 Thank you for explaining that, I went all around the internet but succeded in avoiding the Total site...so, as LDS is not terribly hygroscopic, why is the system sealed, and why are there warnings on the can to (effectively) throw the unused (opened) stuff away.

Or,(quite possibly)are we meant to think óne thíng whilst, actually, the cognoscenti smiles quietly?

Btw- I think that I was being ironic, and I'm sure Smihailex was.
smihaialex   
Mon Apr 08 2013, 05:59pm
Joined: Sep 18 2012
Member No: #1031
Location: Bucharest
 Not very ironic by nature guys, but hey, maybe hanging out w you will develop that side of my sense of humor

Cheers,
Sam

PS: I can really throw away my LDS - I have half a can or so...
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