Rear spheres replacement on XM

noz · Post by **noz** » 05 May 2005, 12:48

Sorry to be a killjoy guys,
Can I add two exceptionally important steps to your sphere removal procedure? These additional steps WILL save your life...literally.
In addition to the 4 wheel spheres which will indeed discharge easily by the above method the Series 2 XM's usually have two more systems you have to worry about, anti-sink and hydractive.
The anti sink valve only changes over when the ignition is either switched on or off. If you follow the above procedure, when the engine is turned off and the car is already at its lowest setting, the anti-sink valve will open connecting the anti-sink sphere to the hydraulics. The pressure stored in the sphere will be released to the struts at the wheels and the car will take a sudden leap upwards. Now, if its on the ground at this point with all 4 wheels and spheres still fitted then its reasonably safe. However, if you've got a sphere off or a wheel off then the resulting ejection of fluid out of the strut or thrusting downwards of the wheelless hub can result in serious injury. The only way I have found to discharge the anti-sink sphere is to set the suspension to the lowest setting, run the engine (very important for reasons explained in a moment), select lowest setting, wait until the car falls, switch off engine, car rises again, start engine, car falls again, switch off engine, car rises again, etc etc. Keep doing this until the car doesn't move when the ignition is turned off (probably 3-4 times). At this point the anti-sink sphere can be considered empty.
Now for the hydractive. We have the same problem here. Pressure stored in the central hydractive sphere on each axle. The internal workings of the electrovalve blocks into which the spheres are screwed are too complex to describe here. There are plenty resources on the web which describe this in full. However, Depending on the condition of various components on the car the hydractive operation may be intermittent. If the car height is lowered and the hydractive sphere is valved off then the sphere will retain its pressure as the wheel spheres are discharged. The wheel spheres can then be removed. However, if someone opens a door or the tailgate the hydractive ecu switches both the electrovalves to the soft mode which opens up the hydractive sphere to the wheel struts with the same consequences as outlined above. If you have spheres off or the car jacked up at this point then you can be in serious trouble. Follow the same on/off procedure outlined above but open and close a door at the same time.
Due to the internal workings of the electrovalve block you must use the engine and hence the HP pump to produce pressure in order to get the car to LOWER. Whilst this might not make immediate sense you either have to accept what I say or go and read up on the workings of the electrovalve. There's a little ball bearing inside which blocks off the leakoff back to the tank unless its pushed out of the way by the pump pressure. Therefore, to lower the car you MUST use the engine (there are some exceptions to this rule but too complex to go into here).
How do I know all this I hear you ask? Well, I'm still alive, just, but everything I've described above comes from bitter experience. I'm not trying to put anyone off DIY, in fact I actively encourage it rather than give unscrupulous garages wads of hard earned cash for screwing your car up. However, you need to understand how the suspension works. Without understanding it you can end up in serious trouble. If you do take the time to learn how it works and follow the procedures carefully then you should have many hours of DIY enjoyment.
This same explanation applies even when you are changing a wheel. If you have a whell off using the age-old standard Citroen procedure (using the suspension up/down technique) be VERY careful that you or a family member does not open a door when the car is jacked up. The hydractive sphere will release its contents to the struts and if your head or hand is beneath it at the time or you've half fitted the wheel and trying to reach for the studs ........... be warned.
I've worked on Citroens for 25 years and Series 2 XM's are dangerous if you do not follow the procedures correctly. I still get caught out even today despite knowing all this.

Hope this helps.
Cheers
noz[8D]

406 V6 · Post by **406 V6** » 05 May 2005, 16:34

T-bird, my friend, if you need a sphere removal tool, i could either borrow you mine - for a small fee [:D] - or they are at sale at Norauto [;)]
Happy DIY!

Post by **Thunderbird** » 06 May 2005, 00:23

406 V6, what tool do you recommend? chain tool or other?
noz, thanks for that important information!
Updating the procedure for rear spheres replacement on a XM mk2:
1. Set the suspension to the HIGHEST position.
2. Turn OFF the engine.
3. UNSCREW the rear spheres in anti-clockwise direction until they start to turn.
4. START the engine.
5. Set the suspension to the LOWEST position.
6. Turn ON and OFF the engine a few times until the car doesn't move. Open a door along the process. Leave the engine OFF at the end.
7. RELEASE the BLEED SCREW on the front accumulator by ONE TURN.
8. UNSCREW the spheres manually.
9. Insert the new o'ring SEALS and dip finger in the fluid in end of susp/unit and run it around the contact face of new seal.
10. SCREW the new spheres manually only (not using the tool).
11. Reset suspension to NORMAL ride height.
12. TIGHTEN accumulator BLEED SCREW.
13. START the engine.
14. About five times "Citraerobics".

crooser · Post by **crooser** » 06 May 2005, 00:30

thanks for the sensible info noz.i didn't know any of that and i am going to do mine this year,so your tips will be welcome.

BX-Basis · Post by **BX-Basis** » 06 May 2005, 02:09

@noz: The anti-sink-valves do not have any electrical connections, so there cannot be any effect of ejecting fluid due to the anti-sink-system. The additional sphere is nothing else than a rear brake accumulator. When system pressure falls below pressure in the suspension, the anti-sink-valves shut automatically, so the suspension is separated from the rest of the hydraulic system. The rear brakes use the pressure of the rear suspension to work. When the rear anti-sink-valve is closed, there is no more pressure for the rear brakes. Therefore the accumulator is installed on the car.
To avoid pressure release from the hydractive spheres to the suspension cylinders it's necessary to set the car to the loweset position for about 2 minutes with the engine running. After that there is no more pressure in the system and all 6 suspension spheres can be removed safely.

FrenchLeave · Post by **FrenchLeave** » 06 May 2005, 02:38

Mandrake, if it's square section it ain't an "O" ring - by definition an O ring has a circular cross-section. Trust me, I spent a lot of years fitting them to aircraft hydraulics.
Following on from BX-Basis's comment; if you do want to exhaust the anti sink accumulator with the engine stopped, why not apply the brakes a few times?

Niek · Post by **Niek** » 06 May 2005, 04:30

I entirely agree with the explanation and method Bx-Basis gives above.
Did the anti-sink just a month ago using this technique (it's a real b*stard (for anyone considering it)!)

Mandrake · Post by **Mandrake** » 06 May 2005, 11:15

<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by FrenchLeave</i>

Mandrake, if it's square section it ain't an "O" ring - by definition an O ring has a circular cross-section. Trust me, I spent a lot of years fitting them to aircraft hydraulics.
<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">
So out of interest then, what would YOU call them ?
Regards,
Simon

FrenchLeave · Post by **FrenchLeave** » 06 May 2005, 15:46

Simple, Simon. (Whoops! I didn't mean it like that!). It's a square-section sealing ring.

BX-Basis · Post by **BX-Basis** » 06 May 2005, 20:50

How about "suspension sphere seal" ?

Kowalski · Post by **Kowalski** » 06 May 2005, 21:06

Apparently they're called "square sectioned ring" rather than "O ring".

AndersDK · Post by **AndersDK** » 06 May 2005, 21:15

'nuff said abouth that sphere seal.
I know I myself keep referring to it as an "O-ring" when I use my humble vikinglishly Shakespear speaking.

noz · Post by **noz** » 07 May 2005, 04:44

BX-basis,
I recognise that explanation now that you mention it and I bow to your superior knowledge. So why is it then that the car jumps when the ignition is turned OFF? Cos it surely does !
Cheers
Noz[8D]

FrenchLeave · Post by **FrenchLeave** » 09 May 2005, 02:49

Anders, I know you said "'nuff said" about the seals, but I must say this: It appears from previous threads (I did a search on "square section") that Citroen fitted both square secton and O-ring seals to spheres, so honour is satisfied all round.
Regarding your reference to your Vikinglishy Shakespear Speak, Your English is immeasurably better than my Danish (or French, or German or whatever)!

BX-Basis · Post by **BX-Basis** » 09 May 2005, 23:33

I never saw any other ring than a "square section" ring behind a suspension sphere. Citroën did not fit simple O-rings, perhaps some sphere manufacturers did.