Evolution: Xantia Hydractive Suspension Regulation - Info

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Jan-hendrik
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Re: Evolution: Xantia Hydractive Suspension Regulation - Info

Post by Jan-hendrik »

I obtained a set of bleed nipples from an ebay seller. They fit just fine and are inexpensive.
[Have I written enough characters now? The site tells me "Your message contains too few characters."] Never knew that rule existed.

http://www.ebay.com/itm/M8-x-1-25mm-Mot ... NW&vxp=mtr

If possible, moderator, please delete previous 2 posts.
I guess I just messed up :oops:
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Re: Evolution: Xantia Hydractive Suspension Regulation - Info

Post by xantia_v6 »

Jan-hendrik wrote: 15 Oct 2017, 12:19 I obtained a set of bleed nipples from an ebay seller. They fit just fine and are inexpensive.
[Have I written enough characters now? The site tells me "Your message contains too few characters."] Never knew that rule existed.

http://www.ebay.com/itm/M8-x-1-25mm-Mot ... NW&vxp=mtr

If possible, moderator, please delete previous 2 posts.
I guess I just messed up :oops:

Image

I have deleted those posts, although you could have done it yourself, there is an icon with a 'x' at the top right hand corner of your posts.

Have you actually installed those bleed nipples? they look rather like the one that is too short. It appears to fit when you screw it in, but the thread bottoms out before the point has sealed.
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Re: Evolution: Xantia Hydractive Suspension Regulation - Info

Post by Jan-hendrik »

Thank you for deleting the posts. The 'x' is not displayed so that did not work out.
I did install the bleed nipples and they were just long enough.
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Re: Evolution: Xantia Hydractive Suspension Regulation - Info

Post by white exec »

Jan-hendrik wrote: 15 Oct 2017, 13:15 I did install the bleed nipples and they were just long enough.

Looks as if they are just long enough. The photo shows the threaded+end length to be c.20mm. My modified M8 bolt was 22mm, a dimension copied from the OE Xantia valve bleed plugs.
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Re: Evolution: Xantia Hydractive Suspension Regulation - Info

Post by xantia_v6 »

I managed to get the new bleed screws to fit by grinding down the diameter of half of the hex section, they were only about 1 mm to short to start with.

Having got that out of the way, fitting the rear hydractive valve was quite simple.

With the car back on its feet, it soon became clear that not everything was working correctly. There was effectively no soft mode in the suspension front or rear, but I could hear the valves humming and, I thought, clicking.

After a few false leads, I found that the rear hydractive sphere (which came with the valve) was ruptured, and refitting my original sphere restored operation at the rear.

At the front, changing the sphere for my original did not improve matters, and I even swapped on another spare sphere which was good last time it was used. Still no soft mode. When changing the front sphere, I noted that the sphere was still pressurised each time, even though the suspension was depressurised, proven by removing a corner sphere. I did notice, without paying much attention to it, that on releasing the pressure in the hydractive sphere, just as the pressure was release, the valve clicked.

About this time I noticed that one of the front corner spheres had also failed with a ruptured diaphragm, it was a NOS Citroen sphere fitted a year ago and not used much since, so they can deteriorate in storage. Fortunately I had a serviceable substitute.

At this point I was going to throw a Lexia at the car to check for any recorded electrovalve faults (the old valves had never recorded any), but had the wrong PC with me, and needed to reinstall the Lexia software. While waiting for that, I leaned on the front of the car, and surprisingly found I had soft mode. I backed the car out of the garage, but a minute later, all trace of soft mode was gone again. Listening very carefully, the electovalve could be heard humming, but not clicking.

Lexia was still installing, so I decided to swap the front electrovalve with another which was previously known good. After this swap, soft mode is back and everything apparently working correctly.

It seems to be an odd coincidence that on both my XM and Xantia, the replacement hydractive valves fitted to the front end of the car have required the electrovalves to be changed before soft mode became reliably available. I wonder if the spring compression fault which often afflicts the electrovalves manifests itself as a loss of soft mode with the later design of hydractive valves?
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Re: Evolution: Xantia Hydractive Suspension Regulation - Info

Post by white exec »

Glad it's working, Mike. Does sound like sticking electrovalves - hum but no click.
Could the internal diode have given out? I think Simon posted a procedure for safely testing (without destroying) them.
Did you have extra protection diodes fitted anyway?
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Re: Evolution: Xantia Hydractive Suspension Regulation - Info

Post by xantia_v6 »

This car does not have extra diodes, I will check (when I get the Lexia install working again) for the associated fault code. On the XM, the electrovalve had no electrical fault, but just didn't work.
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Re: Evolution: Xantia Hydractive Suspension Regulation - Info

Post by white exec »

Both Lexia and the car's own diagnostic only run a very basic check on the EV solenoids: are they present and correct resistance. Won't pick up a sticking one.
Now I think about it, one of my acquired Xantia valves had both a ruptured sphere and a non-working EV, which is what prompted me to re-use the original XM ones. They are delicate little things.
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Re: Evolution: Xantia Hydractive Suspension Regulation - Info

Post by xantia_v6 »

The ECU will usually detect a failed diode in the electrovalve, as the solenoid does not draw enough average current.
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Re: Evolution: Xantia Hydractive Suspension Regulation - Info

Post by white exec »

Not sure how that could work, as the EV is supplied with DC (1kHz, pulse width modulated), and the 'reverse' diode will surely have no effect on the current drawn, nor the d.c. resistance that the ECU sees and checks during its diagnostic run. Only when the supply to the coil is switched off, and a reverse-polarity back-emf spike is created, will the diode do any work (in shorting out the back-emf).

Perhaps I misunderstand, though.
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Re: Evolution: Xantia Hydractive Suspension Regulation - Info

Post by Mandrake »

xantia_v6 wrote: 21 Oct 2017, 19:04 Lexia was still installing, so I decided to swap the front electrovalve with another which was previously known good. After this swap, soft mode is back and everything apparently working correctly.

It seems to be an odd coincidence that on both my XM and Xantia, the replacement hydractive valves fitted to the front end of the car have required the electrovalves to be changed before soft mode became reliably available. I wonder if the spring compression fault which often afflicts the electrovalves manifests itself as a loss of soft mode with the later design of hydractive valves?

In my experience the front electrovalves fail far more often than the rear ones - both the diode and the mechanical part (springs ?) of the valve as well. The failed or intermittent ones I've had have all been front valves - I've never had a rear valve fail.

My theory is it is heat related as it's in a very hot environment between the radiator and engine, while the rear electrovalve is away from any major heat sources. The diode "failure" is not usually a failure of the actual diode itself, but seems to be a poor connection or dry joint on the connection to the diode inside the moulding. The give away for this is that I had one where the diode worked ok when cold but went "high resistance" and eventually open circuit when hot! When it cooled down again it started working again.

Silicon diodes of course don't behave this way - even faulty ones, so it was clearly some sort of dry joint inside the moulding which would fit with long term exposure to heat. Heat could potentially soften the springs as well.
xantia_v6 wrote: 21 Oct 2017, 19:52 This car does not have extra diodes, I will check (when I get the Lexia install working again) for the associated fault code. On the XM, the electrovalve had no electrical fault, but just didn't work.
Even if you think the diodes in the elctrovalves are OK I would still fit the external ones as a matter of course - if they haven't failed yet they will eventually. Also as described above I've had first hand experience of the front one misbehaving when hot, but testing OK when cold - I only caught it as I had monitoring in place while the car was being driven.
xantia_v6 wrote: 21 Oct 2017, 20:38 The ECU will usually detect a failed diode in the electrovalve, as the solenoid does not draw enough average current.
In my experience the ECU will usually detect a faulty electrovalve coil but not a faulty diode. If it does detect a fault it will cycle the valve on and off repeatedly - if you have an LED connected as I did on my first Xantia, you can see this because the LED will suddenly start pulsing between bright (full 12v) and dim (3v pwm) about every second. If you see that happen its a clear sign of a faulty electrovalve.

Mechanical faults like the pin sticking or the seat leaking will of course not be detected.
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Re: Evolution: Xantia Hydractive Suspension Regulation - Info

Post by Jan-hendrik »

My theory is it is heat related as it's in a very hot environment between the radiator and engine, while the rear electrovalve is away from any major heat sources. The diode "failure" is not usually a failure of the actual diode itself, but seems to be a poor connection or dry joint on the connection to the diode inside the moulding. The give away for this is that I had one where the diode worked ok when cold but went "high resistance" and eventually open circuit when hot! When it cooled down again it started working again.
I agree with your theory where you mention the problem is heat related. But in my case, I'm talking about my first XM bought new that I had from 1995 to 2004, the problem was with the rear electrovalve. The rear suspension was supple for a few kilometers after start up and when things warmed up it firmed up. In the hot season that distance became shorter and shorter. In the end I got so tired of it I let go of the car although it had done only 45k km. At the time I did not know about the diode issue/fix. I replaced the suspension ECU and even soldered in new Mosfets, but of course that did not make any difference :(
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Re: Evolution: Xantia Hydractive Suspension Regulation - Info

Post by GiveMeABreak »

I got so fed up with the ride quality (before I knew of this issue - way back in the 90s) that I fitted comfort spheres to both my later XMs just to make it drivable. A design flaw that many would never of known about no doubt, except in the poor ride quality.
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Re: Evolution: Xantia Hydractive Suspension Regulation - Info

Post by white exec »

I guess the solenoid coils generate some heat themselves, which could aggravate the situation.
Wonder whether the diode is actually soldered in, or just cheaply spot-welded.
Has anyone ever opened up one of these solenoid coil assemblies?

Good idea to fit extra diodes and a pair of monitoring LEDs. Can be done in one hit, as it's the same two pins/connections to the suspension ECU multiplug that are tapped into.
DSCF3255_1.jpg
A recent idea for fitting suspension LEDs, without the need to take wiring through the bulkhead/firewall.
The LED pair could be mounted waterproofly in the wiper motor trench, under the scuttle cover.
Under-bonnet switch (LED ground-side) to kill when not needed.
Chris
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Re: Evolution: Xantia Hydractive Suspension Regulation - Info

Post by xantia_v6 »

I have discovered why I needed to change the front electrovalve on the Xantia. While tidying the garage I picked up the faulty valve, and was wondering how to label it when I noticed that the o-ring was missing form the nose. I presume that the o-ring broke while the electrovalve was still fitted to the the hydractive valve. I have no idea where it is now, it probably fell onto the ground somewhere. It would explain the lack of soft suspension.
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