Citroen Hydraulics

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Hiya All Having now worked out how to use a computor, a friend of mine suggested that I might want to have a look at these groups and share some knowledge.
I have been working on Citroen hydraulic systems, from the Citroen DS through to the Citroen Xantia. But not had a lot to do with the C5, So, any questions and I will do my best to give you an honest answer to help you from getting ripped off at the dealers.
Try me you might like it !!!!!!!!
Slim.
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Slim wrote:

Hi Slim,
Welcome! I'm sure your expertise and experience will be most welcome.
Perhaps I can be the first to pick your brains!
I have a 99 Xantia Estate Hdi - the back end sinks randomly when I come to a stop - seems to do it when I take my foot off the brake - it sinks quite gracefully and then pumps back up in 30s or so.
What's broke?
All teh best
Steve
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The problem here is that all hydraulic Citroens use the rear suspenion spheres as rear brake accumulators, if you study the plumbing you will find that the pressure goes from the rear height correcto to the rear spheres via a junction, one pipe from this junction take fluid to the rear brake feed in the brake valve. This means that when you operate the brakes, the rear brakes will have a varied pressure depending on what the rear suspension pressure is, IE if you put some paving slabs in the boot, you will get more pressure in the rear suspension to help lift the car, so therefore more pressure is sent to the rear brakes for stopping power.
This can sometimes be a problem as when doing a long slow stop, then sitting at the lights with your foot on the brakes, it will sap the rear suspension of all the pressure reserve, thus making the car take a dive at the back as soon as the brake is released, then the height corrector tells the car its too low and the car comes back up. (good news the heightn corrector is working fine).
You can demonstrate this yourself. Start the engine, put your foot on the brakes then select high on thr lever, you will find that the front will operate normal but the rear will be very reluctant to go up, release the brakes and the rear of the car will jump up fast. Put your foot back on the brakes and select low, the front will go down as normal but the back will be held up by the rear brakes, release the pedal and the rear will drop like a stone. This demonstrates the effect of the rear brakes on the rear suspension.
As for the problem of dropping, this is normal but not as much as to notice it too much, If the spheres have low pressure especialy the main accumulator this can make the problem worse. The Xantia will typically wear through a set of spheres every 3-4 years.
You could try pleiades at sawtry, I get hydraulic bits there www.pleiades.uk.com
Hope this helps in some way.
Regards Slim
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Slim wrote:

aha! I suspect its the accumulator then ... I recently bought a complete set of 6 spheres (about £20 each from local factors...) and managed to change all the wheel units "ok" but the front and rear centre spheres have resisted my strongest persuasion without doing engineering on them! It takes around 20s to pump up in the morning - also indicative of knackered accumulator ?
many thanks S
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To change the main, simply undo the 12mm bleed screw on the regulator by about 2 x turns (never take it out) then using a good quality chain wrench just undo it. then fit the new one but dont forget to fit the new O ring seal, start the engine run for approx 2 mins, then tighten the bleed screw.
The rear center sphere is the anti sink sphere, (this also doubles as a rear brake accumulator) to change this, set the car in low with the engine running, when settled in low stop the engine and open the 12 mm bleed screw on the regulator, then using the chain wrench, (I use a band wrench I have had for years) you need to undo it, BUT BE CAREFULL this sphere is different to the others, it has a 4.5mm pipe (9mm fitting) going directly into the rear of the sphere, hold a spanner on the fitting and the 2 will come undone together.
Put it all back together not forgetting the seal on the 4.5mm pipe, start the car, tighten the bleed screw then lift the suspension into high and check the LHM level.
Regards, Slim
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Slim wrote:

many thanks Slim
I am slightly concerned at yourcasual use of "simply" and "just undo" ... this car has done 130k miles and everything under the car is getting a bit set in their ways now! I have broken a chain wrench and strap wrench changing the four I have managed to shift, eventually!
There was top tip recently on wrapping a piece of studding round 'em and boting to a piece of dexion or similar - think I'll try that for the remaining two ...
all the best
Steve
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Hi Steve.
Personally I use a Band wrench from Pleiades www.pleiades.uk.com this tool I have used to remove hundreds of spheres, it was a good investment, Chain wrenches are ok but it must be a goo un.
The spheres are not put on tight, its the electrolytic? corrosion between the ally cylinder and the steel sphere, this mixed with a little water and road salt, corrodes like hell.
To remove the rears. Select high, I know it sounds daft but this will hold the cylinder still. Then using whatever wrench you have, turn the shere a little, ie 6 o'clock to 4 o'clock. Thed select low (with engine running) when the system has depressurised undo by hand.
If the cylinders still turn when on high, get a lond soft ended drift, I use a brass drift, Place the drift on the end of the cylinder up to the base of the sphere, give it a good hard clout with a heavy hammer. this will crack off the corrosion and make your life much easier.
My casual use of simply undo comes with these instructions !!!!!!
Regards. Slim
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Slim wrote:

Slim,
Where abouts are you? and do you do any private work?!
Steve (Shoreham-by-Sea, nr Brighton, Sussex)
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Steve.
Sorry but my days of crawling around under cars are gone. I live in Cambridge, the Slim name comes from, when I used to visit Pleiades to get my bits and bobs for Citroens, I used to stop and have a coffee and chat with the big guy in the workshops, we got friendly over the years and called each other Slim, (dont know why) we used to swop knowledge, although I rather think that he has forgotten more than I could ever know about the hydraulics.
I stopped working on cars a while back and the big thing that I miss is not going on my trips to Sawtry to get my bits and chat with the other Slim.
My best advice about working on cars is to get in and get your hands dirty and get the job done!! Too much time can be wasted thinking about the negatives.
Regards.
Slim
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Slim wrote:

Slim,
Like you , I have also (almost) given up doing my own car ... but for some things I just still cannot bring myself to pay ridiculous dealer rates! Basically if it's under the bonnet or in the cabin I'll have a go but without a decent pit or ramps I generally give anything under the car to my local independant garage. They do however (thankfully) recognise their limits and have declined to do anything too "technical" on my Xantia. I attempted to do the rear spheres in the road outside but they weren't coming off without a fight - I got it onto the ramps at work and they eventually sucumbed to a LARGE pairs of swan neck grips ...
These days its the time I lack for these sorts of things ... and I find my 2 and 4 yr olds generally want to 'help' ... etc ...
all the best
Steve
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Just had mine done all round (96n xantia 1.9td estate) (friend of mine who borrows the car regularly, was getting fed up of it taking about 30 seconds to pump up in a morning so decided to do them for me for sphere cost only). Can't believe the difference, 3 or 4 seconds and lthe lights gone. When in the normal position the back end seems a little lower than the front, it drives ok but could there be something not quite right?
Rob
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Rob The only problem there could be the rear height corrector, This little unit sits in the center at the back of the car, I have fitted quite a few of these, and Pleiades tell me that they sell loads of them every week, but in my humble experience, fitting some spheres will not upset the height corrector. Normal failure of the Xantia rear height corrector is failing to rise at the back, this is usually caused by the height corrector siezing up in its cradle and making the plastic link come off.
Your problem could be down to adjustment, but I would reccomend you getting it over a pit or on a ramp to do this as it is dangerous to crawl under a Citroen. Adjusting is easy when on a ramp, slacken the m7 bolt in the anti roll bar clamp and make sure that it can rotate freely on the anti roll bar, then adjust the height corrector itself by pushing the center of the height corrector towards the rear of the car to go up or the front to go down. When the rear of the car is at the correct height, tighten the anti roll bar clamp.
I cant remember what the height is, but if the front is fine, we allways used to adjust it untill the sill was parralel with the ground. Regards. Slim.
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Cheers
I'll give that a try sunday when i finally get a couple of hours free.
For your information, it was like this before the sphere change aswell maybe my initial post wasn't very clear. sounds likt this could sort it. it does pump up. its not as if its right on the floor just doens't seem as high at the back as at the front and also doesn't seem as high as the guy up the roads (exactly the same barring the colour).
Rob
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Correction: the distance between frontwheels and backweehls depends on the height of the car, there's is difference of a lot of centimeters. When you have heighten the car and press the brake the wheels cannot move. When you release the brake, the wheels can turn and the car drops!!! The same occurs from the lowest position going high. Drop the car, press the brake, set the car in highest position, wait for 20 seconds, release the brake and the car will jump. I've enjoyed my children (and backriders) a lot of times with this little trick.
Sorry hydraulic-specialist ;-) I'm just driving CitroŽns with this kind of suspension for only 40 years ;-)
DJ
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Yes and this demonstrates as I was saying the effect of the rear brakes on the rear suspension.
I am not a specialist, Just someone who has had quite a few dealings in the hydraulics over the years.
You can please some of the people some of the time, but not all of the people all of the time!!
Regards. Slim
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Okay Slim, you're my man. DJ
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Slim ( snipped-for-privacy@tesco.net) gurgled happily, sounding much like they were saying :

It's not really that the rear spheres are used as "brake accumulators", in the CX sense of the term.
It's more that the rear suspension is used as the pressure source for the rear brakes, as the suspension pressure is higher when there's more load, hence you get more rear brake. It's actually a very simple and clever way of doing brake proportioning according to load.
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Adrian. You are of course correct is stating that it is very simple load proportioning, much more reliable than the conventoinal type.
I think on my first post it reads as if this is a problem, I didnt realy mean it that way, its just that on long slow gentle braking, then sitting at the lights with your foot hard on the brake pedal, the sudden drop is just something that happens! especially if the accumulator pressure is low.
For some reason this seems worse when facing uphill.
Have a good weekend.
Slim.
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Slim ( snipped-for-privacy@tesco.net) gurgled happily, sounding much like they were saying :

I've always laughed at the back end on ZXs/306s/Xsaras when you put the handbrake on with the car facing uphill....
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snipped-for-privacy@tesco.net says...

Hello Slim,
I have a Xantia ACTIVA ( i'm french so i doesn't know the international name but think they didn't changed it ) and always searched the cause of a so longgggg pressure run-high after starting engine ( about 1 min ) I know that ACTIVA models have 9 spheres in total and normal xantia ( without hydractive or activa ) have only 6, stop me if i'm wrong :)
So ok there 3 more but from about 20-30 Sec to 1 minute there's a difference :-X didn't know someone having the same model to verify. For info the HP-pump and spheres were changed when i bought it last year and it didn't changed anything.
My next car will probably the same model but with a so tinyyy V6 3.0 because the grip of the activa models is fabulous but the diesel engines are really insufficient to ensure "usabillity" of the potential of this car.
Regards
Neomat
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