2.5td Brief Hydraulic History

I've owned the XM for approx 18 months now and although it had a full mot when I bought it I think it must have been suspect. The rear o/s suspension unit had a messy leak and the gaitor was loose. Surely a fail!

Anyway the first job was to get a new (2nd hand) cylinder which I did from A5 Breakers near Dunstable. I can't remember the exact price but I'm sure it was only around the £20 mark. I entrusted the job to my local indie as I didn't want to risk ripping the pipe out! Back the same day £40 cash

When I bought the car the suspension was very firm, not bouncy but firm. There was some movement with a good push, but not much. I read the posts and eventually concluded that the front electro valve was dead. The rear one was buzzing but it didn't help much. I removed the ecu and obtained a couple of mosfets and repaired the card. At the same time I fitted two new diodes as well. When I tried them I had two working electro valves! They didn't affect the suspension though, that was still firm!

Springtime last year I managed to get hold of an accumulator sphere and what I thought were two centre spheres. Unfortunately the centre spheres turned out to be wheel spheres which a local garage fitted for me. The accumulator was a lot better, the tick time is counted in minutes now. However the suspension was still firm because of the wrong centre spheres.

At least I was part way there with some parts rectified and some new parts fitted. The car was booked into a local garage for an mot check in October and I was just leaving home when the steering ram parted company with the rest of the car and smashed the pinion feed pipes in the process. Luckily I managed to reverse onto the drive without losing too much lhm. Another indie job. Trying to do it on my back was impossible and I gave up after three days! Although while it was on the stands I did change the front centre sphere. The car was then off the road for a while pending mot and it eventually passed about three weeks ago, with the suspension still firm on the rear.

Once it was mot'd I decided to get stuck in and finish off the spheres so last week I managed to change the rear centre sphere (two days!) Once you know the knack with these spheres they do become a lot more straight forward. Yesterday morning I changed the two front wheel spheres which took literally minutes each side.

So the situation now is the two rear wheel spheres have to be done to complete the set. In all this time spent bringing the suspension back I've noticed some odd things. After doing the front centre sphere the front softened up straight away. When I did the wheel spheres yesterday it seems a tad more firm now (?!). Didn't George experience something like this? The rear centre sphere also released the back suspension. So I have movement all round now but it still doesn't "feel" right. I bought some hydraflush yesterday so that will be the next job. I have a fair amount of movement now but nowhere near as much as George's video. The movement at the back is about the same as the front now so I won't rush to do the rear wheel spheres. I'll try and use the hydraflush tomorrow and clean the filters. Come to think of it I haven't even checked them yet. I bet they're totally clogged.

In particular I would like to sincerely thank Noz, Techmanagain and Mackay1 for the supply of spares and detailed repair information in this project. However without the help of all on this forum for their support and help this XM might have been long gone. As it is I now have a sound footing for carrying on and sorting some of the other varied problems with it.
Watch this space..................

Nice write up Demag. Unfortunately firm suspension after changing all the spheres and hydraflushing does seem to happen. I had the same experience with my Xantia that had Hydractive 2 fitted. Very occasionally it would give a soft ride but it didn't last long, I changed all the spheres, hydraflushed it, stripped and rebuilt the height correctors and the hydractive electrovalves & blocks.

Steve.

Hi Dave

Nice and useful account.

In my case the car became soft as soon as I took care of resetting the pressure regulator, but then it became hard again the next day after bleeding the brakes.

Perhaps your front now feels harder because the new spheres are standard spec while the ones it had were "comfort" ? Have you compared their centre orifices -the difference will be visible even without measuring-.

The rear should have considerably more travel than the front, perhaps the rear corner spheres is the only factor in the comfort you believe is missing. I would change them anyway, just to narrow down the possibilities...

The hydraflush will do good, just remember, results won't come overnight, mine started appearing at 2,500miles -no difference till then!-.

Keep up with the good work!

cheers
G

Thanks George,

The three spheres I have changed recently are all original three dimple type so I will get them charged. When the accumulator sphere was changed last year it had failed and there was black sludge in the lhm. So I know the system is very dirty. I will try and do the lhm this week because I'm sure any hydraflush at all in the system will help as it is definitely contaminated. I'm going to be busy for a while over the next few weeks (job change) so the spheres will have to wait a while longer and also bleeding all the brakes.

There is a LOT more movement in the suspension now these spheres have been changed. But it is still too firm when compared to my old BX and CX and no where near as soft as the video. However I will just keep knocking the jobs off one by one and following your lead I know it will only get better.

I have just this minute siphoned the lhm out of the resevoir and topped it back up with hydraflush. Done a few citoerobics as well however I haven't had time to clean the filters or bleed the last lhm out. I have to go to Stafford now so I thought any hydraflush is better than none at all and a 40 mile round trip might kickstart the cleaning process. I did try to lift the filter block from the tank but it only came 2 inches as the pipes are tight. As with the spheres, the tank looks like it's never been disturbed before so I dread to think what the filters will be like probably well clogged.

Well it was one joggly ride! I can only think that messing about disturbing the tank and filters has stirred a load of sludge up. I won't be able to do the rear wheel spheres till next month but I will try and clean the filters hopefully next weekend if the weather's ok but this weeks forcast looks sh*te. I was hoping to have felt some difference on the return trip but it didn't happen. Still I'll take it one day at a time and hope things get better. I did have a short wizz up to warp speed though on the way back

Hi Demag

It's very good to have put hydraflush, just don't think about it too much...let it work! Remember, up to 2,500 miles I had not any difference at all in the suspension feeling! Only thing that had improved earlier was the pressure regulator's clicking time from 14 to 28 seconds.

In the meanwhile, reading your account, things you have checked and should be considered as OK, are:

1. spheres: front corner X2
2. spheres: front center
3. spheres: rear centre
4. spheres: accumulator
5. suspension ECU: diodes front and rear
6. suspension ECU: front and rear electrovalves electrically operate
7. suspension ECU: mosfets
8. LHM: replaced with hydraflush on March 9th 2008

Items you have not checked are:

9. pressure regulator: pressure range
10. pressure regulator: leack rate
12. electrovalves front and rear: are they leacky when electrically in "soft"?
13. Flow Distribution Valve: filters clogged?
14. suspension ECU: sensors: do they function as they should?
15. height correctors: leak / internal+external
16. height correctors: car height
17. spheres: rear corner X2
18. suspension cylinders: all: leak rate + wear
19: brake valve: leak rate
20: security valve: leak (rare).

Of course for some of the above you might be able to guess without measuring, eg you say clicking rate of the pressure regulator is "counted in minutes", that sounds excellent (too good maybe?? can you observe at various times and report back in seconds?). Others cannot be easily measured eg cylinders unless you...saw them to see inside. But personally I would try to measure everything that's measurable -if not you might go mad on the way -. The e-valves developing a leak (thus not really pushing open the hydractive valves) was an early H2 material-related fault, you can see with your own eyes under the car just at their outlet points -for the front at least, for the rear you have to look at its return pipe around the area in front of the rear near side wheel-. There must not be any flow whatsoever.

For the record, can you also specify if your car has the old style pump or the 6+2? Does it have anti-sink?

Can you use your radio to tune to the Hydractive and observe the switching between "soft"/"hard" as you drive? I catch it at around 153, LW I think. When in "soft" you should hear an "eeeeeee" sounds, when in "hard" a "bzzzzzz". Of course this method is for initial checking only.

cheers
George

This post has been edited by jorgy9 on March 16, 2008 11:11 pm

I've noticed a few interesting things over the last few days. Accelerating or braking causes the rear to lift or fall as with the BX and CX. However the BX and CX would stop the rear lifting too high under hard braking by opening the rear height corrector and levelling the car. I can't feel any correction in the XM and although the lifting and falling feels more damped and "controlled" the car doesn't appear to level itself as quickly.

If I park the car and lock it, after about 1 hour the rear seems to raise very high (wheel arch about 1-2 inches above tyre.) I would have thought this was a sticky height corrector but the car drives at about the correct height. Any thoughts?

When the car is parked and locked the suspension is very firm with hardly any movement. I realise the centre spheres will be locked out but I would have thought that the new front wheel spheres would allow some movement. Could this be tight struts? Can't really check the back yet as I still have the old wheel spheres on.

Thinking about how much movement there is at the rear when driving, hopefully new wheel spheres should improve it further.

Yes car is anti-sink. So I think that pump will be 6+2 yes?

This post has been edited by demag on March 10, 2008 10:51 pm

My first - and only - thought would be sticking linkage on the rear height controller On second thoughts, maybe a a clogged H/C that could do with a quick removal and swilling out.

I took the filter block out of the lhm reservoir yesterday, stripped and cleaned the filters. They were black but surprisingly not clogged. I can only assume they were cleaned at sometime. I gave them a good clean and refitted today.

Once I'd re-piped I started the engine and did the push pull test at the front and rear. I was quite surprised to notice the rear felt quite soft and I was able to move it up and down with relatively little effort considering the wheel spheres haven't been changed yet. Although the vendor did say he had changed them before I bought the car.

The front which now has all new spheres feels quite firm still. On the push pull test I am getting maybe two or three inches travel and that takes a fair bit of effort as well. (a lot more than the rear). I realise there's a dirty great diesel in there and am assuming lifting it up and down will be harder than the rear but I was expecting more movement than this.

The rear is still high when parked (wheelarch clear of the wheel) so this week I'll see if I can lube the HC linkage weather permitting. When I changed the rear centre sphere I never tried to move it but it looked ok. The spare wheel cradle is still off so access is ok. Spare in boot!

Sounds like mine. There's definite difference between hard and soft mode at the front but much harder and maybe shorter travel than at the back.

So this weekend I stripped and cleaned a spare hydractive valve and pressure regulator (current one had a drip from the bottom mounting). I also stripped and cleaned the electrovalve and checked the seals. swapped over the items and it's exactly the same (except for the drip from the pressure regulator).

One thing I did notice was how green the fluid was that came from the hydractive sphere. This may seem normal but I'm running hydroflush at the moment and this is the second time I've seen this. I'm beginning the think that there's very little turn over of fluid to these parts which if I'm correct means that it will take an age for the flush to work. With this in mind I'm going to buy another container of flush and bleed the system - much like you do with the brakes.

Would I be right assuming that apart from the leakback circuit there's very little true circulation in the suspension side of things? Even if you put the car on low how much fluid goes back to the tank and how much just goes back along the pipes to the hydractive block and height corrector?

Any comments.

Steve.

Sounds like mine. There's definite difference between hard and soft mode at the front but much harder and maybe shorter travel than at the back.

So this weekend I stripped and cleaned a spare hydractive valve and pressure regulator (current one had a drip from the bottom mounting). I also stripped and cleaned the electrovalve and checked the seals. swapped over the items and it's exactly the same (except for the drip from the pressure regulator).

One thing I did notice was how green the fluid was that came from the hydractive sphere. This may seem normal but I'm running hydroflush at the moment and this is the second time I've seen this. I'm beginning the think that there's very little turn over of fluid to these parts which if I'm correct means that it will take an age for the flush to work. With this in mind I'm going to buy another container of flush and bleed the system - much like you do with the brakes.

Would I be right assuming that apart from the leakback circuit there's very little true circulation in the suspension side of things? Even if you put the car on low how much fluid goes back to the tank and how much just goes back along the pipes to the hydractive block and height corrector?

Any comments.

Steve.

Hi Steve

Low flow in hydractive block/low crossflow between left/right sides:
precisely my thoughts as written in my last comment on Hydraflush etc. The crossflow passages (2 paths), which are critical to this suspension's operation, will be the most clogged up especially with UK driving where many cars just go straight all day on a motorway -not good for hydraulic Cits-. That's why I deemed useful to start doing slaloms, along with 10-30 ups/downs a day! Which has worked wonders, just after a couple of days doing it. It also perhaps helps the struts slide better it seems. Anyway I cannot know what effect resulted in what, just that there was a result. Just find a parking or quiet road and apply continuous slight or large changes of direction. I also did it at higher speeds late at night. I'm now trying to think of a way to work the rear block more as it has improved less from this process. Slaloming rearwards perhaps?

I know u say u cleaned the hydractive block, but did u specifically check these 2 paths? One is the main that involves the 2 integrated dampers-tablets and the hydractive piston-valve. The other is the one where the little ball operates (on your H2 car) to reduce roll. I personally have never seen this last path, in real or in photo. Half-a-little ball is obvious on the surface of a hydractive block, but is this the one? It looks very tight in its seat -its possible travel looks much wider in the schematic graphs, although this could be done for explanatory reasons-.

However, if u r sure all else is Ok, and that you have cleaned the hydractive block thoroughly, I'd be really inclined to take a gauge and measure the pressure regulator. You seem very able, don't you have the tools to make one? I know you say there's definitely a diff between soft/hard, but mine was like that *also* before I reset the pressure which instantly made the car as it should be. It was rock hard in "hard", and had some little travel in "soft". I don't know how this difference is achieved as in theory this is an on/off valve.

cheers
George

Depressurising with a door open should almost completely empty the centre spheres of LHM. Perhaps your electrovalve was sticking or only partially opening?

Hi Steelcity

Very interesting line of thought. The pipework is very small diameter and though of great length actually must hold a very small volume of liquid compared to the spheres and resovoir. I guess that when the contents of the resovoir are changed you actually only replace about half the fluid with at least 3 ltrs remaining in the dead ends of the spheres etc. I can only compare this with the microbore central heating system I have at home. If you open a joint in the microbore pipe you get clean fluid because the high pressure flow keeps the pipes totally clean. If you take a radiator out it takes a great deal of flushing to get rid of the black crap that settles out in the low flow area of the radiator. The thought of trying to flush this crap out of the cental heating system via the very thin microbore pipes to the header tank in the roof seems almost impossible and that is without the restriction of a series of fine tolerance valves you find in a Citroen Hydraulic system. I now understand why the Citroen flushing fluid is thinner than LHM and that people are seeking even thinner fluids for a better flush. I suspect that for Citroens where regular LHM maintenance has been ignored each Hydraulic system flush just moves some of the muck to the next obstruction rather than totally cleans the system. It seems to me that rather than seeking thinner fluids we need to identify a few key points in the hydraulic system where we break into the pipework and with a tee piece and valve we bleed off until we get clean new fluid. It may also be necessary to take off system components and clean/refurbish them rather than try to flush the crap further into the system.

Regards

XMexc

This post has been edited by xmexclusive on March 17, 2008 07:16 pm

Hi xmexclusive

Absolutely! -for those of you who can do it -. Those components (for obtaining a soft suspenion) are simply: the pressure regulator, the height correctors and the hydractive blocks. Also, rear suspension cylinders would be nice. As I can only work on my street, I can only content to flushing slowly doing this job.

However with regards to broader -not local- blockage of the piping system -think arteriosclerosis- the only feasible solution is running it on flushing liquid for a lenght of time -unless you want to enter a programme of replacing your pipes with new ones-.

A trick I'll do before putting fresh LHM in mine is to remove corner spheres and leave the old stuff leak from the sphere brackets into a bucket while I am adding fresh LHM in the tank, with height lever on "highest" and engine running. Car should not be able to lift as all the presure will escape from the sphere bracket. This should help get rid of the volume remaining in the hydractive feed pipes which are quite fat.

cheers
George