I have recently changed LHM, accu and pump. All fine so far. Driving along, the car's ride is wonderful. OCCASIOANLLY, even before that, I have noticed an air raid siren noise when the car was rising which stopped as soon as the normal ride height was reached.
I had some air in the rear suspension which was annoying as the tail would go up and down occasionally.
I have bled the system on Saturday, ABS, front and rear brakes to get rid of the problem. Well, the problem seems gone although I just couldn't see any air bubbles anywhere this time. Just a day later or so the siren noises came up again and I noticed the car driving harder. I switched to Sport mode and I swear the ride would get even harder. Then I noticed that the suspension ECU warning light would NOT come on at all, whatever the positionof the switch. Now, I don't use the Sport / Auto switch normally, but something is very odd here. The car otherwise behaves normally.
I put it on low and from there to the highest position. The siren noises come on instantly as it rises. They seem to originate in the front and back near the height correctors but I wouldn't swear. Electrovalves? Noise independently of the switch setting. The noise frequency seems to be relatated to the pressure buildup and once the regualtor cuts out and the ride height is established stop immediatly. This now happens every time it rises. I need to have a closer investigation into this, I remeber the valves clicking very very recently after shutting the door (abt. 1 minute). I will check again asap.
I checked all the fuses in the fuse box, they all seem OK. Unfortuantly I don't remeber the Medium Wave frequency or Long Wave (?) that let me listen to the valves. I tuned in anyway and I couldn't hear anything exactly. That used to be an great Hydractive test. So I suppose they are dead.

Oh our wonderful Citroens, in all my history I never had one where everything worked. The hydraulic system is lovely - when it works. I have come across so many problems in my Citroen history that I fully understand other manufacturers' preference of the ordinary suspension.
But of course, I so much prefer the Citroen ride.

Just weird stuff all this. Sometimes I am really tempted to build a test jig for all the components but I am not a garage and I haven't got infinite time.

Well, if you have any enlightening comments, please let me hear them!

Thanks


Michael

The easiest way to check if the hydractive is working is to close the doors, bounce the suspension, wait for the 'click' and then bounce suspension again and see if its got harder. assuming you hear the click the suspension should have gone harder unless your centre spheres are shot.

If you can remember the sound of an air raid siren - you must be as old as me!

Peter.N.

Well, Peter, grew up in the cold war, so not a WWII vet
What turned out to be was that the complete Hydractive had somehow ceased to work. Why the noises occurred is still a mystery to me. So I studied the circuits to have a go at the system and tried to figure out what might be wrong. Fuses OK, connectors seemed OK. I wanted to have a look at the anti jolt diodes but I really couln't find where they are. Anyhow, I wiggled all sorts of connections around the front and around the ECU, disconnected the ECU and reconnected it. For some reason the whole system came back to live again. In a way that is good but also it is not because I don't know the cause for the problem. The car is a pleasant as ever again.

It is worth listening to 153 Longwave for the sound of the valve. It comes on and off according to the criteria published. Good functional check. Yes, of course the door clunk noise after a minute is also an indicator. But I like listening to the sound while driving to make sure everything is the way it ought to be.

Thanks


Michael

Hi Michael

In the 10 years or more I have been running XMs I have never had a suspension problem, well not an electrical one anyway so cant speak with any authority on the matter, but most problems on XMs seem to be down to high resistance joints. I think the diodes you were looking for are buried in the solonoids somwhere.

I cant be doing with these modern all electronic cars, I dont even understand TVs now and I've been an engineer all my life! The drivers door of my XM has more wiring than the whole of my 1939 Ford prefect did.

Peter.N.

I can understand you Peter. Well, actually I am an electronics engineer myslef but as you say, I am losing it too! THings are moving so fast and if you don't stay with it at all time, that's the end. Just the data book of one chip these days easily has 600 pages!


Michael

Hi Michael,

I can't help alot I m afraid, only to say that I have had that noise for a period but only when lifting the car from "lowest" position on height lever, and only from the rear. It went away after I used hydraflush I think -can't recollect well enough what was that made it stop, as I did various things to the car-. It was an impressive noise indeed -but with no apparent effect on the car's function-.

regards
George