Xantia drops at rear when door opens - updated

andrewc · Post by **andrewc** » 01 Aug 2007, 11:16

Hi everyone,

I have a 1999 Xantia HDI Exclusive, which is fine except for one problem. After the car has been left standing for a while, whenever I open a door (or the boot), the rear suspension drops quickly (the front stays up).

This started a while after I got the car, and would only happen occasionally, but became more often, and now happens every time. At first it wasnt that important, as I thought it may be bad spheres on the back (which they were), but when the problem continued after replacing all 8 spheres, I thought it might be either the rear HA system, or the antisink valve.

There is plenty of bounce left in the car after being left overnight, but as soon as I open the door the electrovalve clicks and the car drops. Last night, I removed the HA fuse and ran the engine for a few minutes. Leaving the car for two hours, when I opened the door the back stayed up. Leaving the car overnight, the car stayed up this morning as well, and there was some bounce in the rear suspension. However, when I replaced the HA fuse (door open, engine off), the back dropped immediatly.

Having looked through the forum, most of the problems with dropping are after starting the engine, but mine didnt drop after starting (if it stayed up when opening the door).

The ride seems fine and the car moves up and down as it should, both by moving the lever and by putting/removing weight into the car.

With the car staying up with HA forced into hard mode, would this mean that the HA system is OK, and the antisink valve is suspect?

Thanks for any help you can give.

Andrew

Mandrake · Post by **Mandrake** » 01 Aug 2007, 12:41

Hi Andrew,

It's highly likely that your rear electrovalve has the "faulty diode" syndrome - there is a HUGE thread that covers just that which you should be able to find with a quick search. (In fact there are a couple worth reading)

The fact that it happens when a door opens with the engine off is the big clue - anti-sink valves cant detect doors opening, but electrovalves (via the computer) can.

Basically what happens when the diode fails is that the electrovalve only switches to the "soft" mode for half a second every time the computer issues a hard to soft mode transition, and then drops back to hard mode.

Because of this the pressure between the middle and outer spheres can become unequalized when the height corrector makes a correction - such as after you getting out of the car and the height correcting down.

Later when you open the door the valve opens for half a second and the car drops when the pressure equalizes.

Diode failure can be complete, or it can be marginal and intermitant, changing with temperature and vibration, giving rise to strange symptoms.

You say the ride is ok, but if you observe carefully you will probably find that the ride at the rear is often not as good as it should be, as the rear will be sticking in hard mode sometimes.

The good news is that there is a relatively straight forward and cheap fix (compared to replacing the electrovalve) which involves connecting an external diode.

Regards,
Simon

andrewc · Post by **andrewc** » 01 Aug 2007, 13:12

Thanks for that, Simon.

I saw this thread about the diodes while I was searching:-

http://www.frenchcarforum.co.uk/forum/v ... hp?t=21720

I've read about them in the past, but I thought as I could hear the electrovalves at both ends of the car, it was unlikely to be them.

You mention the ride might not be as it should, but the back seems to be very floaty all the time, while the front is much stiffer (but not at all uncomfortable). The spheres are the correct ones - they were all originals when I got the car at the end of last year, and GSF gave me the ones for the non-HA car at first, but I didn't notice for a week as the ride was so much better.

Furthermore, pressing the HA switch seems to make little difference to the ride, and no difference at all when the car is standing, either with the engine on or off, I can still press the rear of the car nearly to the floor, but the front only goes down no more than 2 inches.

In that thread, these repairs kits are mentioned:-

http://cgi.ebay.co.uk/XANTIA-SPHERES-HY ... 0136660293

Would these be suitable for fixing it, as I'm not very good with soldering?

Thanks for your help so far.

Andrew

andrewc · Post by **andrewc** » 08 Aug 2007, 10:26

So anyway, I got one of those repair kits and fitted it:

The good news is that the suspension now feels different when the car changes into hard mode. Its not so obvious when driving, but the back of the car seems not to float quite as much (less bottoming out). The difference between the modes is much more obvious when the engine is switched off.

The bad news is that it still drops when the door is opened and the electrovalve clicks - nothing appears to have changed.

It appears as though the HA system is working OK now, so could the problem be with the antisink valve after all? As I understand it is that the valve effectively forms a gate between the front and rear suspension systems, and is only supposed to open when the pressure on both sides of the valve are similar. So, if the valve is opening at too low a pressure, the high pressure fluid in the rear escapes into the lower pressure front part and the car drops at the back. Where else could the fluid be going to?

I checked with GSF yesterday, and they only sell antisink valves for the non-HA models.

Does anyone have any more suggestions about this?

Thanks
Andrew

Post by **RichardW** » 08 Aug 2007, 12:32

I don't think this is a problem with the anti-sink valve. The feed to the rear of the car and the return from the height corrector is routed via the antisink valve the return from the hydractive valve is not however (I know this because my HA valve return parted company over the rear subframe this time last year

). As Simon said above, what is happening is that the pressure is getting imbalance between the (closed eg hard mode) hydractive valve and sphere and the wheel spheres. When the door is opened, the HA ECU switches into soft mode, opening the HA valve - but because the pressure is lower in the HA sphere than the wheel spheres, the fluid runs from the wheel spheres into the HA sphere until the pressure is equalised - this results in the rear of the car dropping - fast!

So, how to proceed from here? I would say that changing the rear HA sphere is the first port of call - however, I see from below that you have already done that (are you sure the right sphere was fitted though?) - which leads me to the conclusion that there is an internal fault in the HA valve that is leaking away the pressure. Trouble is the HA valve is ££££ so it's a bit of an expensive test to replace 8) You could try ringing Plaeides and see if they can suggest anything, or even the guy that runs the Citroen Centre in Oxford who is v knowledgeable in all matters Hydractive. I supose you could try disconnecting the return from the HA valve and putting it in a jar to see if it is indeed bleeding the fluid out (follow the pipe back across the top of the rear subframe there is a joint between plastic and rubber on the near side of the car - very awkward to get to though!), or try unscrewing the HA sphere after it's been stood a while - no pressure here and it will come off easily.

andrewc · Post by **andrewc** » 08 Aug 2007, 15:14

Thanks for explaining it Richard, now I understand whats going on.

The sphere is the right one. It started dropping with the original HA sphere it came with, and despite changing it, the problem happened more often, which suggests it isn't the sphere.

When you say the HA valve is leaking, do you mean the block itself or the electrovalve? I had a look on pr-net and £118 for an electrovalve isn't too bad, but £390 for a new block is silly.

Perhaps one way to test it would be by replacing the HA sphere by a much higher pressure one (ie main accumulator). It wouldn't do much for the ride, but the car doesn't need to be driven to check it's fixed.

Maybe I'll have a look round the scrapyards at the weekend. Living near Pimhole in Bury, there are plenty of them.

Thanks, Andrew.

Post by **RichardW** » 08 Aug 2007, 15:57

Download a copy of Gabor's excellent citguide from here:

http://www.carhelp.info/forums/35292/post1/

(Yeah, I know it's in Cyrillic, but you can read the bit you need!)
This has diagrams of the HA valves. From what I can see, in hard mode the internals of the valve are open to the return line, and therefore the fault must lie within the valve itself

How many miles has it done - has the LHM ever been changed? If not it might be worth a hydraflush to see if that fixes it. Otherwise, I would definitely be onto Plaeides for a refurbed valve, if they do one (http://www.citroen-hydraulics.com)

andrewc · Post by **andrewc** » 09 Aug 2007, 08:54

Looking through that guide, the rear HA block is more complicated than you would think, and I agree thats likely to be the problem.

As for the fluid, the service history was last stamped at 56000 miles, about 4 years ago. Its done 108000 in total. There are some receipts after that, but nothing about the fluid. It looks very dark green, so I'll change that this weekend for some hydraflush and clean the filters.

Andrew.

andrewc · Post by **andrewc** » 14 Aug 2007, 11:29

Hi,

I decided to change the rear HA sphere anyway, and its just as well that I did. I put the car on axle stands (Friday night) and saw there was a small pool of lhm collecting from under the RHS rear wheel sphere. I thought that the seal had probably gone, but I found that the the sphere was loose on the mounting, and I could tighten it up about two full turns by hand, which has stopped the leak. It must have just happened in the past day or two, as it's never leaked any fluid before, and I check the driveway regularly.

Come Saturday morning, I opened the door and the car dropped about an inch, but not to the floor, which is a big improvement. That morning I removed the old lhm and put hydraflush in and, so far, the car doesn't drop at all, even if left overnight. So hopefully, there isn't a problem with the HA block, and maybe I really did have two dud spheres?

So, Richard & Simon, thanks for your help.

Andrew.

JohnCKL · Post by **JohnCKL** » 15 Aug 2007, 22:12

My Xantia used to leap up when opening door or the boot. I think hydraflushing cured it. After 3 years I did another hydraflush. Now seldom have this problem.

Post by **elma** » 15 Aug 2007, 22:21

This is a page from the hydractive manual. I haven't had time to think about it but I think it sounds relevent. Manual is well worth downloading if you don't have it. I'm sure someone else will have the link, I cant find it at the minute.

V- VEHICLE ANTI-JOLT
A - VEHICLE LEVELLING
We have seen that when the supply to the computer is cut, the
suspension is in the "Firm" position (U electrovalve = 0).
Therefore the additional sphere is isolated.
If the pressure in the main spheres varies (passengers getting in or
out, loading dr unloading) a pressure difference with respect to
the additional sphere appears.
When the ignition is switched on, as the additional sphere is
connected to the circuit, the pressure difference translates as a
influx (P additional > P main) or a reflux (P additional < P main)
of fluid in the suspension cylinders, which suddenly alters the ride
height of the vehrcle, and causes the vehicle to jump.
ROLE
The aim of this system is to balance the pressures in the circuits
by energising the computer when a door or the tailgate is
opened for a period limited to ten minutes and timing the
supply for thirty seconds when the doors or tailgate are
closed; the thirty second timer is also activated, doors and
tailgate closed, wh.e. n the ignition is switched off.

Note : If the hydraulic pressure is not sufficient, the
additional sphere remains isolated, which, when the
engine is switched on, can cause a slight jolt.

Note : The anti jolt function is integrated into the
computer.