Interesting Experience With Spheres, Over pressure spheres

HI george,

With reference to the possibility of your struts sticking, I don't know if this will work but why don't you jack up the front left of your car (because that's the side most of the potholes are), remove the sphere and disconnect the anti roll bar link. You should then be able to move that leg up and down by hand to check for binding. If you start off in low position there shouldn't be too much fluid in the leg. Or am I missing something?
As always, I'm too late. Of course you've already ordered a new one. Ho hum, story of my life.
Derek

This post has been edited by DerekW on June 07, 2007 06:17 pm

Hi Derek,

good idea, I was actually thinking of doing this at the garage the day the cylinder is off, and compare side-by-side with the new one, before putting it on car. It has to show then, if there's any difference. Still, I don't know the amount to which those cylinders move freely -even when perfect they might require some force (by human standards)-. I'll find out on the day. My rear cylinder should be with me soon. In the meanwhile, I've read in French forum the story of a guy that found out that the pushrod of one of his rear cylinders had just broken in two pieces! The rod was kept seating in the cylinder's body -it is under pressure till the wheels are in the air and any pressure off the suspension. Actually these days I discovered that Citroen cylinders are quite funny: the pushrod is only held steadily (attached) on the side of the suspension arm. The other side of the rod just goes in the cylinder's body and seats under car pressure on the piston it has to push! It never falls out as it is too long, but if you unbolt the cylinder it just falls in your hands! The front cylinders on the XM are different, both sides are bolted to the car. But DS, GSs and CXs all had the nowadays "rear-style" cylinder in front as well.

Another important discovery is that the rubber bushes on the rear subframe of the XM are known to become loose (because of rust i ntheir metallic parts). I suddenly remembered that last summer at hte MOT, when the mechanic was moving the wheel in all directions to check for free play, I noticed the side-pieces of the rear subframe were moving together, up-down, like they was loose! (He didn't notice anything, the wheel had not free play itself as it is attached on the main axis). Specifically, the piece that was moving was the "sub-subframe" that receives the cylinder (not the main axis where the suspension ram bolts on). I had forgotten that, but is now on the top of my list. I read it is possible (on the XM) that the points of welding of this piece have rusted so badly that the tend to part with the main axis...

regards
George

Here's the relevant post from L Kimberley in the yahoo XM-L:

" Finally - drop rear subframe and replace the mounts - the front ones have
detached from the round steel ring through rust and allow vibration. You should
be supplied with the later type round mounts and later rear square mounts from
S2 - kit 90 GBP. Your front ones Β may be solid round the later ones have a
square inner profile. The important bit is that the metal plates in the rubber
are in line with the cars front center. Call me if you need to discuss this
aspect when you get the new mounts I am just doing mine now as have had to
replace subframe with one from S2 -- you may have to do this as well, rust will
be expanding and forcing the steel plates apart on the arm pointing points.
HopeΒ isΒ you may just save it by welding, while subframe down replace all rear
spheres and rear height adjuster 90 GBP. Plus fuel filter! Β Yup its a mission
but S2 subframe amounts allow a bit of self steer so should improve steering. "

Symptoms he had:

" General resonance vibration from rear of car like wheels out of balance - which
I had balanced. The mountings do rust and the rubber becomes loose so sub is not
as tight. On cars 10 years on the rust on the inside edge of each of suspension
box is a bigger problem as it may push the arms out of line.

Just drop subframe but leave all pipes connected and front mounts are beaten
out and new ones pulled in with a bolt and plates. "


G

Hi George,

Referring to a post in a different part of the forum, could a faulty sensor (steering, brakes body sensor, etc) be causing your problem by making the suspension go into semi-permanent hard mode?

Derek

Unfortunately no, as I've repeatedly driven the car with a voltemeter plugged in each of the electrovalves pins o nthe ECU, and the values and pattern of electricity is absolutely correct -and car was hard-. This has been resolved (for the front) after putting a new electrovalve and putting a one-way valve to feed the hydractive valve with high pressure, proving that the problem was hydraulic. The rear electrovalve still plays up, it probably leaks like the front one, or, doesn't take enough pressure due to loses in other places. That's partly why I want to change struts with new -and other bits, progressively- to reduce leaking in the system.

Yesterday Friday, very hot again in Scotland (22+), and the car was soft. Plus, I noticed that the height correctors were correcting extremely faster than usually, e.g. when getting out of car the rear was correcting after 2-3 secs -when it's usually working after a minute or so-. This is directly not relevant to the softeness issue, but indicates to me that other valves are working better when temperature is higher than 20ish. Could be that LHM flows better. So, more indication that the problem is somehow LHM-related. I think before putting the news cylinders on, a run of Hydraflush is prescribed on my car -and it seems its effect will be maximal now in summer, rather than in cold winter-.

regards
George

It'll be interesting to see how you get on with the hydraflush and whether it gives the continual soft ride you are searching for.

If your problem does appear LHM related - what have you been running on up to now? LHM or LHM+ ?

For what it's worth, mine ran with hydraflush for 1500 miles and now has OM15 aircraft hydraulic oil in for the last 1000 miles without any drama. The OM15 appears less viscous (much like hydraflush) and appears to make the damping much softer and the way I like it.

/runs for cover as the 'you can't use anything apart from LHM' posse advance on me

Ok, have put the hydraflush, and car is now very soft. Not-normal reactions to small irregularities remain, but car is otherwise lovely. PRessureregulator clicks @24secs instead of 13 just before. Rear drops slower overnight and never really bottoms.

So once again I witness the "new LHM" effect, which has been reported in many places I read. There's a debate on whether this effect is due to 1/ air naturally entering the system when doing any hydraulic work and then blocking some leak point/route, possibly related to the brake system, or, 2/ just the quality of new LHM as opposed to old one. I for myself have not had the opporutnity to separate those 2 effects as I have always done some work on the system whenever I chnaged LHM. But this time the agrage pumped the LHM from the tank and only filled up with Hydraflush, so actually there's no the "air in the system" factor. I can see this from the braking behavior also, usually if there's air it goes and seats at the rear beakes and you get the car lifting its rear at every bite of the brakes. Now my braking is normal, i.e. flat, so no air overthere. So it appears new Vs old (20,000mls) liquid made the difference, which I can't explain. Citroen advises LHM to be renewed each 40,000mls (60k kms).

Expecting now to see the also typical gradual deterioration of this miracle back to "before" standards, within a week or two. Pressure reg. cycling time shopudl also return to previous time. We'll see. The only related clue to this issue I've seen was in a French BX forum were a guy was reporting that after having changed every bit of the hydraulic system and being in desperation with a "crashy" suspension stil lthere, he noticed one day how the brake doseur emitted a noise when activating the brakes, similar to liquid flowing. He put a new brake doseur and his BX never became crashy again. He from his part suggested the doseur sucked air in the system which made LHM too bubbly. Who knows...

So I'll now do some 2,000mls on hydraflush and by the end of August put on my new cylinders -don't want them to be infested with dirtiness-. I nthe meanwhile I'll look at the rear subframe bushes.

regards
George

Hehe, already today the pressure regulator cycle has returned down to the usual, 14secs. The front still behaves, but the rear has become crushy again.
G

hmmm, today I topped up with 1 litre of Hydraflush (they hadn't properly filled it up in garage) and regulator cycling time became 35secs....

G

Sounds as though the Hydraflush has a higher viscosity, unless its just because it was cold, see what it does when you've done a few miles.

Peter.N.

??? you got the garage to drain the LHM and fill with hydraflush??

For someone who's dabbled with FDV's and pressure regulator rebuilds I thought this was well within your comfort zone?

/If you want it doing properly, do it yerself

...I do whatever I can by myself but sadly don't have the time/the bigger tools...Any time I have, is spent in finding what they need to do and telling them to do it...Last evening my girlfriend said "I wish u hadn't bought this car, u'd have done so many other things" as I was seating on the pc browsing the usual forums...She's probably right...

BTW, this morning already, the regulator cycling is down to usual 14secs and car crashy and not so soft, as before. It was not crashy the day before I top up Hydraflush, while was cycling again at usual 14secs, the only difference I see is today it's well colder. Well, if next time it gets hot it becomes soft again I'll have a strong hypothesis there.

G

Ride today is near almost 100% to the crashy pattern. Something is going on with the LHM in my car...my car is doing something to the liquid. I changed it of Friday, 5 days of driving and car gradually deteriorates to previous state. I'm thinking of writing a letter to Citroen France, they will probably know what's the problem.
G

Have you previously ruled out air bubbles in the LHM/hydraflush?

This post has been edited by rowanmoor on June 20, 2007 08:31 am

No I haven't -I know the theory u refer to-. But this, or the sticky struts, are really the only two possibilities left that could explain this behavior. Although I wouldn't know why, if it was sticky struts, the fresh LHM allows them to work well and then situation quickly deteriorates to the previous state in a matter of days. Hhmmm, add the temperature scenario as the 3rd possibility.

If it is the air in system it would be easy to check out as the likely fault is in the LHM tank-to-pump pipe. Also the pump itself could be absorbing air (I've read it elsewhere). All other parts of the system are under pressure so would leak LHM rather than suck air in.

regards
George