Sphere Damper Elements: Can They Fail?

Unread post by **CitroJim** » 25 Mar 2011, 20:58

Following my epic rad battle, I've been using my Activa on a daily basis this week. Until this evening it's not been as enjoyable as it should be.

The reason for my lack of enjoyment has been a very floppy back-end that felt like the spheres had been replaced with lumps of jelly. It was neither floaty, comfy or pleasant. In fact it made driving the car feel like piloting a boat across a rough sea. It would even roll a little if provoked.

Activas should be very taut and tight in all four corners and mine was far from that. It felt incredibly under-damped - like a conventional car with duff shockers. A shocker it was...

I knew there was a problem a couple of weeks back as I noted there was no real difference between hard and soft mode at the back. There's a clue here and it felt as if the rear was stuck in soft mode. It wasn't as all checks showed the rear Hydractive electrovalve to be very happy and working normally.

I checked all the rear spheres for pressure and found them all within spec.

I've spent hours this past week trying to work out a plausible reason for it. Running against a brick wall as it were, I swapped the rear corner spheres as really they were the only thing left that could cause it.

Although I had no genuine Activa ones, I did have a set of Genuine Citroen NOS Hydractive Estate rear corner spheres and popped those on.

Result? An absolute transformation

The rear became as tight as a drum and there was a very distinct difference between hard and soft modes. A test drive showed just how much better it was and a test drive at speed across a little hump-back bridge I know where previously the back would bottom out caused the back to move not a jot.

So, conclusion is that the rear corners, despite being healthy pressure-wise had a problem. They are definitely corners and appear to have the right size of damper hole for rear Hydractives but they clearly have no or little damping which is the major task of the corners on a Hydractive even in soft mode.

Therefore the question is, can the damping elements fail or wear? It's a new one on me but there's a clue looking at the spheres; the disc around the damper hole and the damper hole insert itself on these suspect spheres is loose and spins freely. All other corners in my stash have very tight discs and damper hole inserts...

There's a bit of history with this pair of spheres. When I first got the car, the rear end was a bit floppy and under-damped. A pressure test showed these spheres a bit down and I replaced them with new standard GSF ones. The spheres in question were re-gassed items that had been supplied by a company that does not being with P. I duly sent them off to a company that does begin with P for a re-gas and then stored them for a while. In time, I found my old V6 had non-Hydractive rear corners fitted and one day popped the GSF spheres off the Activa and fitted them to the V6. To the Activa I fitted the freshly regassed spheres. Things seemed OK initially but as I was driving the Activa very little at the time I may well have not noticed the under-damping was back.

This must be a very unusual problem. Has anyone else experienced it as it's a new one on me

Sorry for the long post, I'll be very interested in your thoughts.

Deanxm · Unread post by **Deanxm** » 25 Mar 2011, 21:17

Strange one Jim thats for sure, surely to be too soft fluid must be moving too freely, there are damper units built into the hydractive block, two of them which regulate fluid flow from each wheal cylinder to the Hydractive sphere and these are identical to the ones fixed to the fluid port of the corner spheres.

One thing i have seen was the bypass hole of one front XM corner sphere opened up by the ingress of dirt, the face of the damper looked like it had been shot blasted, my guess is dirt got in during a sphere change and then spent a long time being shot back and forth through the damper damaging the port and damper assemble each time it did but this is highly unlikely.

Now you come to mention it the XM has a very soft back end and when pulling away it sometimes drops near enough to the stops which isnt right really and it has become very wondery just lately but then its coming off the road for the summer for subframe removal and box oiling so that will be sorted, i digress

What about if you removed the roll bars would that not soften the ride somewhat? since the Activa has the ability to remove the rollbars fixed link could it not theoreticaly roll far more than the average car if things went wrong rather than resist roll?

D

Unread post by **CitroJim** » 25 Mar 2011, 21:49

That's some interesting points Dean

A good point about the dampers in the sphere block during soft made. having a look at some technical documentation suggest they're not for conventional rebound/bounce damping but more to damp the fluid movement from strut to strut during hard cornering; in effect they act as a bit of an anti-roll system. As far as I can tell, in soft mode the damping elements in the corner spheres do the vast majority of the rebound damping.

The thought that muck in the system could abrade the dampers is very reasonable and it might account for the loose discs and inserts. It's not happened in their time on my Activa as the hydraulics are squeaky clean but who knows what old wreck they may have been on in a previous life.

Or could it just be wear and tear and there's a limit to how long a corner lasts because of this? Is there a re-gassing limit because of this?

On your XM, the suspension should switch briefly to hard when you accelerate away under the influence of the throttle pedal sensor. Depending on, assuming yours is Hydractive I, how fast you press the go pedal determines how long the system switched to hard mode. It varies from upwards of a second. It might be worth a Lexia session to check the throttle sensor is working correctly... Can you feel it switch hard when cornering vigorously or when you press in the sport button?

Yes, although the roll system is working perfectly on mine now, I have experienced an Activa with the system inoperative and it rolled like a 2CV and dangerously. It was one of the many faults on my first Activa and I nearly put it in a ditch as a result bringing it home. I did not know how an Activa felt then. If the rams are not properly pressurised, due to the roll corrector being seized at one end, then effectively the roll bars are not there. I said mine rolled previously but only a bit, nothing like a normal car or even a normal Xantia but by Activa standards it did roll!!!

You'll find, with yours, when you drive it properly, that it gives the sensation of being very firmly sprung and damped although this is an illusion. They ride beautifully but are very, very taut and feel almost rigid. Like a conventional car with very hard springs but without the eye-ball rattling and teeth grinding that normally accompanies it.

Deanxm · Unread post by **Deanxm** » 25 Mar 2011, 22:13

What are you asking Jim? are you asking if my Hydractive Citroen is stuck in soft mode?

It does switch to hard, but sometimes, like today, the electrovalve starts vibrating so harshly that it can be heard above the rather loud music i had on and could be felt through the seat and floor, its still energised and giving a soft ride but i have to manualy switch it into sports to stop it and then it will be fine for months again, this may have something to do with it but im not really that bothered.

Your underdamping is strange though, as far as im aware only the sphere's can affect damping, or fitting smaller rear cylinders, they havnt shrunk have they?

D

robert_e_smart · Unread post by **robert_e_smart** » 25 Mar 2011, 22:47

are you asking if my Hydractive Citroën is stuck in soft mode?

The best thing I ever did to my TD Xm

addo · Unread post by **addo** » 25 Mar 2011, 23:05

I will assert that the thin damping washers in a Dee sphere (whether removable or riveted), do fatigue and fail.

Surely something like this is possible on the Xantia?

DickieG · Unread post by **DickieG** » 25 Mar 2011, 23:24

I reckon that that particular pair of sphere''s are duff Jim as when I fitted them to the Activa it never felt right so I contacted the supplier (oop norf) but didn't find them overly helpful. Funnily enough I did ask the same question about dampers wearing out several years ago in the Citronean but never had a reply.

Have you pressure checked the sphere's again this evening?

Unread post by **CitroJim** » 26 Mar 2011, 08:16

DickieG wrote: Have you pressure checked the sphere's again this evening?

yes and they were fine on pressure...

I suppose I can recycle them as accumulators... Seems such a shame really to throw them... Wonder if Mr. P can remove the dampers from them so that can be used in a new role? They'd be perfect as centre spheres or Activa balancing spheres then...

addo · Unread post by **addo** » 26 Mar 2011, 08:38

If you used the end plug and centre hole as the means to drive/centre on your lathe, first you could turn off the burred-over damper retaining ring.

This may be all that's needed, as I think the damper disc has the thin washers riveted through it only.

Pleiades · Unread post by **Pleiades** » 26 Mar 2011, 12:56

Hi Jim.

Yes the damper can break and often do, that is why we allways check them before re-con.

The damper unit consists of a plate with holes drilled at angles and a series of shims on either side, all this held together using a rivet with a hole in the middle.

The undamped fluid goes through the hole in the rivet, this is the bypass hole and allows you to run over things like cats eyes without feeling them.
The shims are set up so that the fluid goes into the sphere and has to lift the shims on the inside to get through, on the way back out it has to lift the outer damper shims.

These shims can break off causing the damper unit not to work.

If you remove a sphere damper and turn it over, you will see that it looks the same both ways round.

You can cut the damper out and bin it, then the sphere can be charged to the correct pressure and used as an accumulator sphere, this we often do when spheres have damaged dampers, wast not want not!

Regards
Martin.

Unread post by **CitroJim** » 26 Mar 2011, 21:20

Thanks Martin,

Excellent

The central damper rivets are very loose in both of them...

Next time I'm over your way I'll pop them in to you as my lathe won't be able to chuck up a sphere to cut out the dampers

I need a couple of rear centre Hydractives and they'll be just the job for that with a bit more gas in them.

They're still resplendent in shiny Pleiades Green so you won't need to paint them