In another thread Demag asked why I was running on hydraflush for so long (5,600 miles today). The answer is simple: I didn't know what else to do to regain the suspension's softness.

The day I adjusted the pressure regulator range to 145-170 bar, the car became soft straight away, meaning the problem was simply that the hydractive valves were not opening with the pressure of 137-157 bar my regulator yielded. I drove around for the whole day -so unearthy was the new-found feeling that this suspension offers-. The next morning I bled the brakes. To do that, I kept the car for about 2 hours on "highest", engine running. Something has happened during that, because afterwards the car became not-so-soft again. I spent a period rechecking all visible, "measurable" things on the car: hydraulics, electronics, all confirmed OK. This is the critical part of the story:

http://club-xm.com/forum/index.php?showtopic=894

I have to thank God because, having seen the suspension operating properly for 1 day, easily I discarted scenarios like rear bearings gone etc. Obviously it had been able to be perfect, so the apparatus was in good condition. I'd perhaps got rid of it by now if I had never experienced that.

In Septemeber 2006 I raised the cut out pressure of the regualtor to 177 bar -above the max specified- wanting to see if it was a low-pressure issue. This didn't result in anything good, and on a December 2006 check I found that my front electrovalve had become leaky when it was not, beforehand. So this is a no-no. I put a brand new e-valve then.

In spring 2007 I fed the front e-valve directly from after the pressure regulator and also put a one-way-valve to this feed line -I wanted to test if it was a matter of the whole system being leaky and not able to keep pressure tightly, with the result of the hydractive valve closing back in bumps etc-. This improved the front very slightly but it was far from being OK. So lack of pressure to the e-valve not the problem.

So not knowing what else to do, I put hydraflush for a second time in summer 2007. I had run a session of hydraflush when I got it in 2004 but this didn't yield other results except of stopping some external LHM leaks -a sign that things were really blocked and narrow in there-. In the meanwhile, I started bying new struts and height correctors whenever there was an opportunity, as I couldn't think of what else to replace.

After about 2,500 miles (summer 2007) I was about to throw again the flushing liquid as there was no improvement on the suspension -although the regulator cycling time was going up, from 14secs to 28 today-. Then, suddenly, I started getting "soft days". So I decided to leave it in and see.

In the meanwhile I started reading french citroen forums looking for cases like mine. The UK Cit forums are full of BX and Xantia struts binding, but no reference to the XM. Most importantly, I was surprised to discover two things, in the french space:

1/ in France it is common practice to advise (Cit dealers and indies alike) leaving the hydraflush for far more than the max spedified (3,500miles) if the car is older or the problem not solvable by other means (new spheres etc). I read a few testimonies of people running DSs, CXs, BXs, and Diravi'd XMs on hydraflush for many years and miles (from 14,000mls to 100k+), without their hyraulic circuit having had the slightest sign of deterioration. Also, it is commonly advised for "weekend" cars to run permanently on hydraflush. This made me 100% more confident to leaving the product in for an indefined period of time. At the end, it was not worthwhile owning a Cit that is about as hard as a standard car. I didn't want comfort spheres, had tried them before, they are very comfortable but the car totally floats about and its dangerously vague out of the motorway. The proper XM style (experienced for 1 day!) is that the car rides just flat, you just don't feel anything really; no floating, no bumps. Like running on glass. Even when turning you don't get the feeling the car is rolling -very weird-.

2/ I got to know this "Hydronet 2000" product. This apparently was used from the Cit network overthere till recently. You just add about 10% of volume in the dirty LHM and go. then you throw away all and put LHM in. So 1 cycle of emptying/cleaning is skipped. However what was much more interesting for me was that many XMers (this was in planete-citroen) swear by it. It seems it's way more efficient than hydraflush. The XM linked in my signature has been cleaned with Hydronet 2000. The owner (moderator of hte XM-thread) says an XM doens't get better than that. As the firm making it (Hafa) doesn't do retail, they did a group buy and distributed it among themselves. I'm lucky as my sister is working in Paris and as I definitely wanted to try it out I quickly arranged her to get me a 5lt (40eu) of it and hand it to me when we'd meet in Athens, in Christmas-time. And so hapenned. Chemically, this seems to be parafin-like, it definitely says it is a product of petrol on the spec sheet which I attach (in French). Smells like petrol basically. It is transparent with a grey shade. It is "for cleaning hydraulic circuits". This is a photo of the tank I got. All the label at the rear says is:

" Removes dirtinesses and varnishes and disperses them in the hydraulic circuit.
Fluid for cleaning hydraulic circuits that function with mineral oil, without stopping the operation. Add while in operation (from 5% to 15% depending on gunk-ing) "








I added a glass of Hydronet 2000 500miles ago. The immediate result as I dropped it was that the pump became less noisy. On the longer run, it is my impression that the car has progressed in leaps since. I now see an improvement each day I drive it. Of course it could be that the cleaning was almost accomplished anyway. Or that I have increased the number of "citrobics" I do from about 10 to about 30 each day -wherever I park/leave, it's an opportunity for citrobics-. So I now have a mix of Hydraflush (85%), Hydronet 2000 (10%) and LHM.

Changes I've observed as the car improved:
a/ Yesterday specifically it was a milestone day: I got back the feeling of the car riding flat, undisturbed, in full control. The body just doens't move, it's the wheels that do.
b/ I also got another funny effect: having put the car on "highest", then moving lever to "lowest", the strut that's on the side where I seat reacts a tad faster -drops first-. I tried to capture the effect on my mobile camera but it's limit, you can just feel it for a millisecond then both sides drop at the same pace. This, as far as I can think, indicates that the struts have got to a point of ease of sliding where they have become sensitive to my weight. This is now a permanent feature and it never happened before, I'd have noticed it.
c/ Also, now the front drops almost as fast as the rear after parking. So the cylinders are leaking, but at least not gripping. d/ Another noticeable change that gradually became perceivable was that the front compresses a bit in anything more than gentle braking -and decompresses when releasing the brakes-. In the past the front was definitely not moving the slightest unless braking hard.
e/ Another change: car now lifts from lowest to highest in an near linear manner, fed by the pump only, the regulator only cuts out for 1st time near the point where max height is achieved.
f/ Another one: if your Cit makes too much noise from the tyres specially in rougher tarmac, it is likely that the cylinders are binding -seems they transmit all high frequencies to car body-.
g/ Also now the car clearly moves up by 1-2 cm when I go out of it, to be followed by the height correctors intervening and lowering it back. Before it bearly changed height when I entered or went out of it. This effect is more pronounced to the rear, and happens everytime to both front and rear when 2 people go out of the car. When it's only me, the front might not correct its height (I'm about 9 stone).
h/ Finally, the height correctors are now silent, absolutely. In the past I could hear the rear correcting from a few meters off the car at the supermarket, doing a "ffssssshh" noise. Now it's zero noise, you just see it dropping.

Now, what had happened to my car? I can be certain that:

1/ the front middle sphere WAS opening, as the difference with the "hard" setting was absolutely there.
2/ the cycling times of the pressure regulator didn't seem to matter. On other soft days I had 14secs, on other ones 28, same for hard days, it didn't corelate with softness.
3/ the front cylinders binded: a/front stayed up for many hours in the exact same position after parking (non-antisink car); b/when raising the car, the pressure regulator cycled several times in tune with the front moving in steps. This means that the front cylinders generated a binding counterpressure of 170bar!
4/ as I said, the suspension performed excellently for 1 day, so I knew my cylinders *had* been OK, and the rear bearings also.
5/ I knew the front e-valve had secure high pressure to the specified values and still the front was not soft.
6/ I had rechecked throughought 2006-07 all the front spheres and accumulators for the fear one might have gone burst but they were all good, about 10% lower on pressure, nothing else.
7/ all electronics worked as they should -I had spent some time driving around with a voltmeter plugged on the suspension ecu (did both front and rear e-valve pins) observing the voltage behavior and it was absolutely as it should-.

What I believe happened:

1/ putting the car to highest for 2 hours engine running, with the new increased pressure of 170 bar, somehow mobilised residual dirt (from the height correctors I guess) which has been spread everywhere, making cylinders sticky, blocking hydractive blocks.
2/ because of the same, perhaps the cylinder seals have been permanently damaged and made the cylinder sticky somehow.
3/ perhaps height corectors were so dirty that they didn't fully close when stabilised, so part of the pressure escaped back to the returns.

The empirical clues:

1/ all this time, the front of car clearly assumed a soft position *softer* than the "hard" mode, but still it was not so soft -when pushing by hand, when driving-. Front hydractive valve gunged up and not opening to full?
2/ the first day I felt the rear softening, I "lost" a quantity of LHM> gone to fill up the rear middle sphere for first time.
3/ all those changes described before, that I think point to the direction of struts binding. Most annoying effect was the inability of the wheels to absorb the smallest road disturbances, when they seemingly did better in larger ones.
4/ the really gradual day-by-day improvement of the car fits with the process of something being cleaned away, if not anything else. Totally different to the immediate softening I got after tuning the pressure regulator.

So, it seems this Odyssey that started March 2006 is coming to a close and I'm now driving my XM with a smile up my ears. I won't be writting again about this story, only putting my experience to the disposition of others. Hope though that many can be helped from what I've written in the same way I've been helped by other accounts I read all over the net.

Anybody wants to buy off me 2 new front cylinders, 1 rear, and 2 height correctors? Only jocking.

cheers
George

Don't suppose you'd like to sell a glass of that 'Hydronet 2000' stuff would you George?

Or do you have any suggestions as to how a can of it could be aquired?

My suspension is nothing like the car in the video , or like your description of your new found suspension .

Paul.

Hi George,

Thanks for taking the time to produce that detailed and informative write up.

I too, am now wondering is my suspension doing what it should be. Its soft yes, but certainly not anything like you describe with driving on glass etc...

Hmmmm

Ciarán

George that is absolutely fascinating. Thankyou for all the valuable info.

Years ago (pre-hydractive) I bought an early Cx 2000 (my first ever Citroen ) It was in a state when I bought it, the suspension was solid. All the spheres were totally shot. I drove it home about thirty miles and the only suspension was the air in the tyres! When it hit a bump in the road it literally bounced into the air! I rang the local stealer and asked them what the problem was "Change the spheres" they said. Huh? What are spheres? "Those big green things" they said. Over a period of time I did the rear arm bearings and changed/gassed the spheres. The ride was superb, everyone who went in the car said how good it was. Then some rep in his Maestro tailended me and wrote the car off!

I bought my first DS with the proceeds. Well if the CX was good then the DS was other worldly! At 50+ mph it really was magic carpet territory. I ran a few of them and the suspension was brilliant. I later moved to a BX Leader. Once again the suspension was superb (I had to do the arm bearings on that as well). Then I had a break from Cits for some years. As I got older and the kids grew up and left home I had more time and decided to get another one and that was when I bought the Xm about 18 months ago I think. When I picked it up I was immediately struck by the firm suspension, not hard crashy but just firm. The vendor told me he had changed the rear spheres and had the box to show me. But the rear is firm to this day, I do have the rear centre sphere yet to do though.

This car is like a rolling restoration and I have only scratched the surface yet. My first big breakthrough was repairing the suspension ecu last year. I have changed the front centre sphere and think the wheel spheres will have to be done as well. But the back is my main problem as it is very firm. I know one sphere had collapsed and the system is full of black gunge but I don't want to hydraflush untill I have the spheres all done.

You have given me renewed hope now George knowing that there is "a way"

Thanks.

Hi George.

I can't help but think that something similar must be used in the hydraulics industry.

Your description sounds just like my Xantia was.

Lovely write up. Well done.

Steve.

After a quick search on the subject of flushing hydraulic systems, it seems that there's a distinction made between flushing the fluid and flushing the system. I reckon that flushing heated hydroflush could be the way to go if we can't get hold of Hydronet 2000.

I think that rigging up an external tank and heat source could be done or alternatively substituting a container for the LHM tank and then putting in a small element heater. As the fluid heated up it could help thin the 'sludge' and so help the flushing. I quite fancy trying it to just see if it works. Obviously too high a temperature could be damaging so it would need to be monitored closely.

Steve.

Sorry to post again but one thing that strikes me about this flushing of the hydraulic system is that we don't back flush them unlike cooling systems where the usual advice is to removed the radiator and back flush it. Would it even be possible? Some parts could be I guess but valves and such like no. Disconnecting some of the joints should allow sections to be backflushed, a good summer project perhaps?

Steve.

Hi all

I'm glad bits and pieces of the post echoed some of your suspicions. This said the suspension problems in an XM are finite, and well documented in the "Self-Help" section.

I'd like to remark that, despite I got into an obscure situation the day after bleeding the brakes, in reality I had managed to obtain a perfect suspension with very small effort and money, by March 2006. All my 140k XM had needed was in reality:

1/ a fresh set of spheres -unfortunately one cannot try to do any other fault-finding if he is not certain that there's a base of good spheres-. Or at least, a fresh set at the front, if you want the minimum to start with.

2/ two diodes on the ecu -most XMs seem to need them at some point of time, and it's now easy with Roy's kit on ebay-.

3/ the pressure regulator tuned back to the specified pressure range of 145-170 bars. This costed me a few pounds because I needed to obtain 2 old regulators to get the needed shims from.

In reality, the key intervention that made the suspension soften from one moment to the other was the pressure regulator tuning. The problem was simply that the pressure range of 137-157 bars I found it was returning was just not enough to push open the hydractive valves. This is very encouraging if we take into account that the hydraulics were filth dirty, that all my 4 cylinders are leaking, the brake valve leaks, and perhaps the height correctors also (don't know), and that the car had previously run for at least 20,000 on flat spheres. Shows the system is not so sensitve after all. The only extra element in a typical standard steering-assisted XM (bec mine is Diravi'd) is the Flow Distributor Valve, but even this is no rocket science to refurb, and even a bad one will show less if the pressure regulator provides sufficient pressure.

I just browsed the "Self-Help" files and found that pretty much all that go wrong with the suspension is covered, except of:

1/ refurbishing rear cylinders
2/ tuning the pressure regulator
3/ a dummy-guide to diagnosing if initially the electrovalves are OK electronically.

I have not knowledge of (1/) as I've never done it, but I could write guides for (2/) and (3/) -just be patient-.

cheers
George

As for the "Hydronet 2000", I'd be absolutely glad to share it but only brought 1lt with me. If there's sufficient interest, I think the best is to try and get a 5lt (it only comes in 5lt afaik) and distribute it among us. Given that the XM's LHM tank takes approx. 4lt, a fair dose of Hydronet for 1 rinse would be 400ml. So a 5lt would suffice for about 12 fixes. This would cost about £3/dose, p&p not included.

However the main problem remains how we get it to the UK. My sister got it delivered to her office by ordering at the local branch through courrier for about 15eu. I'm not aware of how one can get a liquid substance from country to country. I know the Post doesn't do liquids, and courriers neither. Anybody any ideas? I suppose I could ring the makers in Paris and see what they have to propose.

So, anybody interested, can you please pm me with quantity *ideally* required and I'd see if we have a feasible case?

If there's not too much interest, I'd hapilly send a couple of doses from my own to people in trouble.

cheers
George

Steve

flushing with warm Hydraflush -this would be very interesting, I'm curious on the results-. I have no idea why we don't backflush, I guess it's just not necessary.

I guess doing ups and downs (Citraerobics) exactly speeds up a great deal the cleansing of pipes and valves. If you think of what's happening when the car lifts from lowest to highest and back: new liquid is forced at a high speed through the correctors and hydractive blocks, then leaving this to return to the LHM tank, where it is somewhat cleaned by the filters.

I wonder, if, say, I took my XM, and did this repeatedly for many hours, for a whole day, at the end of the day would I have the same result I have today after 5,600 miles? Because it seems to me that the result of the cleaning agent circulating as such is 100 times more drastic than the car operating normally for many miles (ok, the brake valve doesn't get to be cleaned, but you could also be depressing the pedal for a whole day ) ??

I guess even as soon as next weekend you could set up the Hydraflush warmer and maybe pay the son to be doing ups-downs for a couple of hours! (can he be trusted? )

cheers
George

Hi all

I think the main thing to consider when using a flushing agent, as Steve has pointed out, is that the fluid needs to be hot. I'm sure that with my car only doing tiny mileage and all short runs the flush will never get warm and so the whole process will take much longer than it would for a 'mainland' car which is allowed to run longer and thus get hot with every run. Maybe a fish tank heater or something could be fitted to a spare lhm tank to warm the oil to 30 or 40oc (do fish tank heaters get that hot?) and speed the whole process up???
Also do you think that the most crucial parts to keep clean would be the small damper valves within the system, small pieces of dirt would play havoc with the ride, this could be the trouble with people suffering a sudden loss off softness as small pieces of crud pass through or get wedged in the damper ass. Ive noticed small pieces of crud that seem of a reasonable size (not many) in the lhm tank at flushing time, maybe back flushing these components would make perfect sense. It would be a lot of work to do though Steve

Dean

You might end up being seasick doing that for a whole day George!

George I will take 4 doses of Hydronet if it's available please. One for now. One when I finish the spheres and Hydraflush. One for the new Lhm and one spare .

I think if this product is as good as they say, and I have no reason to doubt that, surely the company must distribute internationally?

I also did a search on system flushing and saw the hot flush. The only thing that might cause concern is we are not running a normal hydraulic system with a propriety oil such as Shell Tellus and we come back to the old problem will the hot flush damage the Seals? Could be VERY expensive if it does .

As dealers & indies use clean petrol to clean LHM tanks and components, why wouldn't a small dose of petrol into the exisitng fluid in the LHM tank carry out a similar process on the whole system? It would certainly thin the LHM safely for a short period.

Do we know whether hydranet 2000 or hydraflush contain any detergents?

I'll clean my filters, give some petrol a try and then see how much (if any) more crud comes out on the filters again after a week or so. Might not be that conclusive for my cars though because I already run them on OM15 hydraulic fluid and have done so for 2 yrs now I find it's slightly lower viscosity has a self- cleaning effect.

Over to you guys who use straight LHM+

I was thinking of the best way to heat the Hydraflush when I thought about the old heated screen wash gadgets you could buy. So what I may try is to build a heat 'exchanger' that will absorb the heat from the cooling system and pass it to the LHM.
There's a couple of possibilities here, first would be to use plumbing fittings or 10mm pipe and create a spiral around the top hose that the LHM pump return has to flow through. Alternatively fasten a piece of copper tubing to the top of the radiator, say 28mm to act as a reservoir with reducers each end to fit the pump return pipe. Does anyone know if LHM and copper react?

Any comments on this hair brained scheme?

Steve.