Suspension Behaviour, Or misbehaviour!

[Ciaran]

Good evening folks.

I've noticed over the past week or so, the car's ride getting a little harsh sometimes. The rear has been slightly bouncey for a while, so I know it needs new spheres, and the front sphere's history is unknown, so I'll replace them too.

However, I'm wondering if I had the dreaded 'stuck in hard mode' problem, as the ride quality has noticibly deteriorated all of a sudden, it wasn't a gradual thing.

Quite a lot of times, when I've driven the car, then parked it in the drive, about 10-15 seconds after I lock it and walk away, I hear a light 'Ssssssssssssssss' sound, and upon examination, I find that the noise is the front of the car gradually sinking, by a few centimetres, then the sound trails off, and it stops, settling at 'normal' height. Its as it its been riding too high or something.
However, on the other hand, I was thinking the drop in height could be due to the centre sphere opening, however I've had that happen before and it normally causes a violent lurch up / down, never a gradual, controlled descent like that.

Has anyone else experienced that phenomenon shortly after stopping the car?

Cheers.

Ciarán

[Peter.N.]

Could be that a sphere has failed completely. If they are already low the inflatable part can puncture leaving complete loss of movement. Try bouncing each corner to see if there is movement, which should be equal across each axle but not necessaraly front to back, then try it again with a door open, this will put it in soft mode, you should have more movement, if you havn't, it doesn't automatically mean that you have electronic problems, flat centre spheres will give the same effect.

Peter.N.

[Ciaran]

Thanks Peter, will do so tomorrow.
I'm really beginning to suspect the front ones now....

Will see what happens when I bounce it.

Cheers

Ciarán.

[DerekW]

I used to get this with my previous cars, DS, GS (several) and BX. It was simply the car rising as my great weight got out, then the height correctors sensing it was too high and lowering it to normal haight. I've never noticed it with the XMs but the same thing must happen. My missus used to say the car was sighing with relief after I'd got out.

I'm just thinking off the top of my head (it's sherry time again) but you should be able to do a bounce test, with the engine running, with the system forced into "soft" and "hard" mode to see if there's any noticeable difference. You can force it into "soft" mode by opening a door or the boot.

Derek

[jorgy9]

Yes, the hissing is just the car correcting its height, mine does it and especially the rear is sensitive to one passenger in car; front, depends on the ocassion, but you always get it if you have two front passengers unboarding.

You should actually be happy the car is hissing because it means your spheres are soft enough for the car to lower when you get in and to lift when you get out; it also means your middle spheres valves are opening, it doesn't do that if relying only on the corner spheres.

Regarding the hardness, you can also think of the scenario of a sphere having had a hole in its membrane, it can happen if your spheres are low on gas. I had it once on a front corner sphere and the feeling was awful at moment when car was in hard mode, the front would judder like a kangoroo. Are you able to say if it's all the car that's hardenning, or is it only the front or the rear, and when (ie in soft or hard mode? , or "all the time 10 mins after I start up". It's not too difficult to narrow down the possibilities...

regards
George

[Ciaran]

Hi Derek, George, thanks for your answers.

Thinking about it, the car only does the rise / drop thing if I have passengers, I don't think I've ever seen it do it when its just me. Glad to see its normal behaviour though.

Well, I tried the bounce test yesterday and the back seems fine, doing a nice soft 1.5 oscillations when pushed. The front however, is a different matter entirely. Very little movement when I push it, and shoving very hard (to the point where it feels the metal of the wing is going to bend), makes little discernable difference. Even with a door open there is little change, so I think its safe to say, that at least one, or perhaps both side spheres at the front have had it.
No problem, will get some new ones ordered up this week. Which does bring me to my next question, how to ensure that you get the right spheres for the car?

Cheers.

Ciarán.

[jorgy9]

http://www.myparts.org/

[Peter.N.]

I would say without doubt, front centre sphere. GSF £19.50 + vat.

Peter.N.

[Ciaran]

Looking at it that way Peter, it would be foolish not to change the centre one when doing the sides anyway, so add that to the list. Is the front one as nightmarish to get near as the back?


Cheers

Ciarán.

[Peter.N.]

GSF Spheres :

Front, normal N45324. Comfort N45328. Centre N45322.

Rear, normal N45358 Comfort N45328A. Centre N45344.

Tell them what car and they will make sure you have the right ones. They do a very good mail order service.

Peter.N.

[xmexclusive]

Hi Peter

Is there a difference between the types for the rears of saloons and estates?

Regards

XMexc

[Peter.N.]

Hi Ciaran

I didn't notice that you had replied - sorry. I changed both my centre ones last week. The front one I fitted in '05 but it had failed, the rear one didn't look as though it had ever been changed. As I was replacing the exhaust at the same time it made things a lot easier, as with the exhaust off the rear one is quite easy to get at, but it was well rusted and the chain wrench wouldn't touch it, but a lump hammer and sharp cold chisel into the weld around the centre in an anti clockwise direction (looking from the top) very soon shifted it. The front one came undone very easily as it was somewhat oily, its just a fiddle to get the chain in. As the front one was completely flat I had no trouble with fluid pressure, the rear one though, gave me a liberal coating of LHM.

I dont find that there is any need to depresurise the system other than to put it on the lowest suspension setting with a door open, this keeps the electrovalve open. One the car has settled right down the only pressure remaining is that contained in the sphere, just undo it a few threads until the fluid starts to dribble out and go away and leave it for 10 minutes, you should then be able to unscrew it by hand.
Make sure that you fit the new rings in the top of the cylinders.

Peter.N.

[Ciaran]

Hi Peter,

Many thanks for the sphere part numbers, makes life much easier!
Ta for that reply detailing how to do the job also. I'll do as you suggest, and just leave the car in low with the door open. Regarding that though, don't the electrovalves shut off after a predetermined period of time, like the interior lights, to save battery power?
Ok, so you'd hope it wouldn't take more than ten minutes to unscrew a sphere, but this is me we're talking about!

Regarding taking the spheres off, I just have a standard chain wrench, the type used for oil filters. Is there a special wrench needed for spheres (I understand GSF sell one?)...

You mentioned new rings on the top of the cylinders.... sorry to ask a stupid question, but what are these? I'm presuming they're rubber sealing rings that go into the neck of the sphere or something?
You wouldn't half know I've never changed one before!

Cheers for all the help.

Ciarán.

This post has been edited by Ciaran on March 26, 2007 10:28 pm

[Peter.N.]

Hi Ciaran

The suspension system probably does switch itself off but it doesn't take long to depressurise. Once the suspension is right down plus a few minutes, you can shut the door. There will still be some pressure in the centre spheres, unless, like one of mine, they are completely shot.

The rubber seals are supplied with the new spheres, the reason I mentioned them is because the are supplied on the thread of the sphere, but as you will see they are not a tight fit, so take them off and fit them in the rebate on the housing, otherwise they may get trapped and damaged. You will see what I mean when you get them.

I doubt that an ordinary oil filter chain wrench will move them unless they have been replaced in the fairly recent past or are oily. I have one which I made from a section of motrobike chain, or there is a tool available, someone is selling one on ebay. Failing that, you should be able to loosen then using the 'hammer and chisel' method and then unscrew them with your chain wrench. When refitting, only do them up hand tight.

Peter.N.

[DerekW]

Mine came off easily using a standard chain wrench so you may be lucky. If not and you don't fancy using a cold chisel and hammer, I read somewhere that another way is to tighten a large jubilee clip around the major diameter and then clout the protruding screw housing on the clip with a large hammer. My preference would be to do this via a drift rather than trying to hit the screw direct. Either way, once the initial seal is broken the sphere should unscrew by hand.

Derek