Replaced my flat accumulator sphere, still getting a bumpy ride

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kenbw2
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Re: Replaced my flat accumulator sphere, still getting a bumpy ride

Post by kenbw2 »

I'm going to have a bash at fixing my electrovalve. It's been suggested in this post to disassemble it, and stretch the spring inside it so that's my project for the weekend.

So it's:

- Lower the suspension
- Open the pressure release valve screw at the front
- Jack up the rear
- Remove the spare wheel
- One 13mm bolt to remove the spare wheel carrier(?)
- Locate the electrovalve
- 16mm socket to remove the valve

Then refitting is the reverse of removal.

Any tips and tricks before I have a go at it?

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xantia_v6
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Re: Replaced my flat accumulator sphere, still getting a bumpy ride

Post by xantia_v6 »

As mentioned elsewhere, the two alloy parts of the valve that screw together have loctite on the thread at the factory. I have dismantled about 6 of these over the years, and one damaged the alloy before the loctite let go, so if in doubt, heat the valve in the oven to soften it before applying too much force.

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white exec
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Re: Replaced my flat accumulator sphere, still getting a bumpy ride

Post by white exec »

Yes, go gently with the vise (very gently) and spanners/grips. The aluminium is very soft.

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Stickyfinger
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Re: Replaced my flat accumulator sphere, still getting a bumpy ride

Post by Stickyfinger »

white exec wrote:
05 Dec 2019, 15:18
The aluminium is very soft.
Is a massive understatement, it is like warm Butter !

kenbw2
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Re: Replaced my flat accumulator sphere, still getting a bumpy ride

Post by kenbw2 »

The local independent Citroen specialist mechanic has had some availability sop instead of me fudging my way through it I've given it to him to check over.

He's removed all 8(!) spheres and the electrovalves and found that most of them are a bit low, but the rear ones are completely flat. To make matters worse the hydractive electrovalves are not getting their correct voltages.

Hard part now is sourcing local Aussie spheres!

Spheres

Front suspension strut spheres
Correct: 45 bar
Actual: 30 and 33 bar

Rear suspension strut spheres
Correct: 30 bar
Actual: 0 and 0 bar <-- this is my bumpy ride problem!

Front Hydractive sphere
Correct: 75 bar
Actual: 60 bar

Rear Hydractive sphere
Correct: 50 bar
Actual: 32 bar

Front accumulator sphere
Correct: 62 bar
Actual: 75 bar <-- looks like I have the wrong one!

Rear Anti Sink sphere
Correct: 50 bar
Actual: 14 bar

Hydractive electrovalves

They're receiving the full 12v burst
They're then going straight down to 0v
They're not seeing the reduced voltage at all

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Stickyfinger
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Re: Replaced my flat accumulator sphere, still getting a bumpy ride

Post by Stickyfinger »

Diodes blown ?

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white exec
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Re: Replaced my flat accumulator sphere, still getting a bumpy ride

Post by white exec »

EVs should be getting 12v for 0.5sec (current approx 3A) followed by "3v" (current approx 0.5A). The 3v is actually 12v at 1000Hz and 25% duty cycle (a pulsed waveform, to hold the solenoid closed without overheating it), and will show up as approx 3v on a good digital voltmeter, or an old-type moving coil testmeter.

The d.c. resistance of a (disconnected) EV should be approx 4.8 ohm.

The internal diodes (embedded, not serviceable) usually fail open circuit, so with one failed like that you should see the same d.c. resistance whichever way round the test meter is connected. WIth a working diode, the figure will be different one way and then the other. Diodes failing 'short circuit' are unusual.

The diode needs to be working...
(a) for the protection of the output stage of the suspension ECU, to prevent it being damaged by the EV solenoids switching off
(b) for the correct operation of the solenoid "hold-in" under the reduced pulsed voltage.

If in doubt about the diiodes, simply add extra ones (400v 6A is a very durable rating). They are very cheap. Connect "inverse": band/stripe on the diode to EV+ from the suspension ECU, other end to a good Gnd. One diode for each EV. Easiest done near the ECU connector.

The EV solenoids have polarity marked on their brown 2-pin connectors, + and - moulded into the plastic.
Observe polarity. Do NOT apply 12v directly to the EVs in an attempt to force them to stay closed, as this will damage them permanently.

The EV outputs from the suspension ECU can be checked with a 12v LED or small 12v bulb (5 watt). You should see 0.5sec of full brightness, followed by dim running.

If you have to replace the suspension ECU, make sure it is the correct version, and for Xantia (not XM). Version number will be marked on the ECU case.
__________

Unfortunately we don't have circuit diagrams for the suspension ECUs themselves. Experience is that the output transistors on the ECU output (which directly supply the EVs) can go faulty. They can be replaced with good quality ones (beware cheap versions) if necessary. For details of this fix, go to club-xm.co.uk.

First, though, run a Lexia check on the car, and see if any faults are thrown up.

The car should run its own suspension check as soon as the IGN is switched on. If the suspension light on the dash is flashing (or fails to light at all), it indicates a fault. It should light for a good few seconds, then extinguish. The ECU does run a self-diagnostic check on the EVs, but this is limited to seeing that they are connected, and not shorted/disconnected.

Check that the two multipin connectors on the ECU have clean contacts.
Check that Ground connections are clean and sound.

kenbw2
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Re: Replaced my flat accumulator sphere, still getting a bumpy ride

Post by kenbw2 »

All fixed!

Because parts are hen's teeth things have had to be a little creative.

- The guy managed to find a pair of new new front spheres, so they've gone on.
- He also found some second hand hydractive spheres, so they've gone on.
- The anti sink sphere I brought with me from the UK has gone on.
- He managed to find a correct accumulator sphere, so that's on.

Which left me with my original problem - my completely flat rear spheres.

A car club friend had acquired the spheres from a nearby scrapper so we gavce them a try, but unfortunately they were very low pressure.

Then the thought occurred to both of us. Those low front spheres I had at 30 and 33 bar. They're the right pressure for the rear corners!

So with them on I've had a complete overhaul of all of my spheres! amazing!

It left the issue of the electrovalves. He tried exciting them with a 3 second 12v burst and for reasons he isn't entirely clear on that's sorted them too.

The car's a dream to drive now, it's amazing! I no longer fear bumps in the road and speed bumps are a thing of beauty.

Happy ending, even if it took a while to get there!

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white exec
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Re: Replaced my flat accumulator sphere, still getting a bumpy ride

Post by white exec »

Glad you got it sorted.

Thanks for detailing the electrical gremlins on the XM site. Sounds as if your reserve suspension ECU wasn't needed after all. At least you have a very valuable and usable spare.

The front and rear corner spheres are just about swapable on Xantia saloon:
FF are 400/45/0.7, and RR are 400/30/0.6,
so if pressures are right, the springing will be ok.

The 0.7mm aperture means the FF spheres are slightly less damped than the 0.6mm at the back, to cater for the sheer weight (inertia) of the engine. It's a small difference, though, as spheres go . . . . and certainly better than nowt!

Full list of sphere specs for the car here, if you don't have it already:
Citroen Mechanics' handbook viewtopic.php?p=590278#p590278
Go to Xantia 2, and hit the '2001' to download the pdf.

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Re: Replaced my flat accumulator sphere, still getting a bumpy ride

Post by Hell Razor5543 »

Yay!! Well done. Now have some fun with the handling and Sport mode!

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Re: Replaced my flat accumulator sphere, still getting a bumpy ride

Post by Activa TCT »

Good to hear it's working now.
Solder those diodes in tho on all solenoids, they fail for no reason and are sometimes ok, sometimes bad

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white exec
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Re: Replaced my flat accumulator sphere, still getting a bumpy ride

Post by white exec »

Activa TCT wrote:
18 Dec 2019, 10:54
. . . on all solenoids . . .
Yes, but at the white ECU connector end. Too difficult and unprotected underneath.