Xantia Activa Bouncing

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DHallworth
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Xantia Activa Bouncing

Post by DHallworth »

The rear end on my Activa seems to bounce horribly.

I thought the car did it and a friend of mine confirmed it for me on Friday.

The Activa system seems to be working fine, with the engine running and pushing the car from the side there is no body roll all the flex is on the tyre side wall.

When driving along and you get to a bit of bump road the back end will go up and down like its boucning, even when on the motorway.

If on the back road with the sports suspension on when giving it some beans if you go over a bump the back end will go up n down several times. It's almost as if the dampers are flat on a normally sprung car.

The car is a 1998 R Reg Series 2 Activa with 45k on the clock. I bought the car in December with 37k miles on the clock. All of the spheres are bright green and rust free so am assuming they aren't originals.

Is this the sign that the sphere could be flat? Or is it likely to be something else?

Thanks in advance for your help guys!

Regards

David.
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Post by AndersDK »

Be sure to do the Citaerobics before you decide for any repair.

The Activa model has the hydractive suspension, which has nothing to do with the active antirollbar cylinders. The 2 systems are completely separated - except for the hydraulic pressure source.

A hydraulic Citroen will start bouncing and be too soft with a harsh tendency to bottom out - when the spheres have lost too much pressure.
next symptom will be a hard suspension.

You know that the hydractive system will revert to its park mode, which is hard, approx 1 minute after the engine is turned off. In this state you do NOT have the extra axle sphere connected.
If your Xantia is very (too -) soft to jerk down in the rear suspension in the park mode, you should immediately suspect the wheel spheres.

Note : its the spheres ONLY that provides the suspension. Cylinders, correctors etc. do not influence on the suspension, only the height.
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Post by andmcit »

Just to be totally clear, is the ride almost rigid where it won't so much
bounce as judder/patter over road irregularities or is it almost too soft
being wallowy where the travel almost feels like it'll bottom out?

If it's uncomforably hard (especially at the rear) for me it points to a duff
rear centre sphere electovalve stuck in a locked hard setting out of sync
with the rest of the suspension. It may even be an internal problem with
the suspension computer as I've discovered on my Activa!

If on the other hand it's wallowy, I'd suspect incorrect spheres are fitted;
it's difficult to work out at first which sphere is which if you've not worked
on an Activa before!

Andrew
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Post by CitroJim »

I quite concur with Andrew. It may be just a need for the diode mod on the electrovalve. Can you hear the rear electrovalve clicking/humming when in soft mode? Basically if you open and close a door after a period of time with the ignition off, the electrovalves should switch to soft mode with an audible click followed by a low hum. After 30s they will click off and return to hard mode. When in soft mode the rear should be significantly softer than when it is in hard mode. Run the engine and let pressure establish and then switch off and shut the doors. Bounce the rear. It should be soft for 30s and then as the electrovalve clicks off it should then go hard.

This link may help. It's in French but it shows the sphere positions on an Activa and gives some useful electrovalve information.

In French, the Activa system is called SC/CAR. Not to be confused with anti-sink which is known by the French as SC/MAC.

If you need to fit diodes, it's much easier to break into the loom in the ECU box.
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Post by KevMayer »

I've had a look at my suspension ECU today. Mandrake did some really good pictures of the position to connect diodes, but, the wires he connected to were white. I don't have any white ones. The ones on my ACTIVA are red.

The wires to my front hydractive 2 electrovalve are yellow and green. So, does anyone know where the diodes haveto be connected ?

That's a great link Citrojim. I've printed it off. Now I just need to find my french dictionary.

Does anyone know how the suspension ECU knows when a door has been opened ? Is there a direct link from the door sensors or does it look for current flowing in the interior light circuit ? I've found that I have no bulbs in my B pillar interior lights, and I keep getting strange results when I try the bounce test. Yet, when I opened the boot, which does have a bulb, the suspension switched to soft mode, so, did the bulb current trigger the ECU to switch on the electrovalves.

I can hear both my electrovalves buzzing when I turn off the engine and close the doors. But, the front electrovalve stays in soft mode for say 10 mins. I wonder if the ECU thinks theres a door still open.

Next step is to get some interior bulbs fitted and try again.

Cheers, Kev
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Post by CitroJim »

Hi Kev,

As far as I know, the hydractive ECU takes door signals from the interior light courtesy switches except on the hatch where there is a separate switch (a little plunger in the latch mechanism) as the boot light is actuated by a tilt switch.

10 minutes I think is the door left open timeout to prevent discharging the battery. I'll take a stab it's the boot switch causing the problem. They're a bit on the fragile side.

I've still not fathomed out how MK2 courtesy switches work. There are none visible and even breaking a dead Mk2 Xantia did not reveal the secret!

Electrovalve Wiring: Some had white wires (MK1s usually) some had grey (MK2s mostly) and indeed others have red.

Look for the numbers on them. 7720 is the front electrovalve, 7730 is the rear electrovalve and 7723 is the Activa electrovalve. Attach the kathode (banded end) of a diode (such as a 1N4004 or similar, not critical) to each of these wires and attach the anodes of each diode to an earth wire (green with yellow bands) as per mandrakes pictures. Use heat-shrink sleeving to insulate well and you'd be surprised at how big a soldering iron you need, especially on the earth cable. All that copper and a cooling breeze is enough to defeat a small soldering iron. A good gas one might be better than an electric one.
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Post by DickieG »

citrojim wrote:As far as I know, the hydractive ECU takes door signals from the interior light courtesy switches except on the hatch where there is a separate switch (a little plunger in the latch mechanism) as the boot light is actuated by a tilt switch.

10 minutes I think is the door left open timeout to prevent discharging the battery. I'll take a stab it's the boot switch causing the problem. They're a bit on the fragile side.
The Hydractive boot switch is separate from the boot light switch, its located under the plastic latch cover and works by the cover sliding down and pushing against it. I've found two instances now where there have been problems with this switch, on one the locating tag had rounded causing the switch to stay open, on the other the boot lock was simply out of adjustment. You can test it by unplugging the switch then connecting up an Ohm meter shutting the boot and viewing the meter through the rear window.

You can test both the door and boot switches at the ECU by unplugging the white connector, terminal 6 is the boot switch and 7 the door switches.
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Post by DHallworth »

The suspension on the car feels like it is ready to bottom out.

I left it locked on the driveway for around 30 minutes tonight and then went back to it, pushing down on the boot spoiler i can get it to go right up and down.

The travel in it is fairly huge.

It feels like it is ready to bottom out when pushing down on it.

If you go over a bump on the motorway doing around 70 it will go up and down several times. In a really really soft wallowy mode.

Thanks Guys

David.
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Post by andmcit »

I'd say that's totally wrong by a long chalk - sounds like quite excessive
movement that could alter the cars' ride and handling - I don't get that
kind of movement on my normal SX equipped suspension estates and
certainly not my VSX saloons.

Can you determine if there is anything stamped or in fact printed onto
the new looking spheres David?

One for Simon/Richard/Jim here - Is it possible that the metal discs that
are effectively the 'jets' of the hydractive spheres have been deliberately
removed from the centre sphere block on the rear? :shock:

On a different 'tack' - is the anti roll bar attached to anything on the back!!
I bought a 24v V6 Xm a few years ago now with the most fabulous soft
ride on the front - that is, right up until the point I discovered someone
had either deliberately removed or forgotten to replace one of the front
droplinks...

yep, totally and altogether and completely MISSING!! :shock:

fitting one certainly tautened up the ride on the Xm's front end, that's
for sure!! Felt like a backward step actually. ;)

Some previous owners can be quite creative sometimes - I recall a
GSA I bought many moon's back now that had a bit of a list and it wasn't
obvious at first what was wrong but it rode OK(ish). Found that to stop
one of the rear pipes to the back ram leaking, instead of renewing the
pipe, the remains were very firmly hammered flat for a long length
sufficient to prevent massive leakage of high pressure fluid though it
was slowly managing to make it's way out...

necessity being the mother of invention and all that!! :roll:

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Post by DickieG »

The rear end of an Activa does tend to feel rather soft and wallowy compared with other Hydractive Xantia's, I've looked into this issue in depth on mine, checking the Hydractive system electrically and hydraulically, sphere specification/pressure etc.

I wonder if it's a combination of Activa rear sphere's have a slightly larger damping hole (0.7) than standard Hydractive sphere's (0.6), the effect of having a very firm front end not allowing the body movement sensor to switch the system into firm mode as easily as standard Hydractive Xantia all leading to a feeling of imbalance.

Or could it simply be that in Citroëns' desire to produce the headline of a "No roll car" it meant that the front end has to be so stiff that the only way get an acceptable ride comfort was to make the rear extra soft so that it could effectively be "levered" by the front end (does that make sense?) otherwise customers would question "What's the point of it all"?
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Post by DHallworth »

I remember my dad had an Activa from 8 months old and his never bounced like this one does.

Will try spheres as they are only £20 each and if its just the rear wheel ones its gotta be worth a try.

D
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Post by Mandrake »

KevMayer wrote:I've had a look at my suspension ECU today. Mandrake did some really good pictures of the position to connect diodes, but, the wires he connected to were white. I don't have any white ones. The ones on my ACTIVA are red.

The wires to my front hydractive 2 electrovalve are yellow and green. So, does anyone know where the diodes haveto be connected ?
No problem - it's pin 1 and 2 that are the front and rear electrovalves (with their returns going to earth, pin 8/15) as per my pictures, so you just need to identify which wires they are if the colours are different.

Just unplug the plug from the ECU (disconnect the battery first) and use a multimeter, and by using a fine pin you can poke into the wire you suspect is the correct one through the insulation and measure from there to the contacts on the plug.

Make sure that you unplug both electrovalves at the electrovalves themselves before doing this, and use a low ohms range to check that the reading is really zero, and not a few hundred ohms due to return paths through other circuitry.
Does anyone know how the suspension ECU knows when a door has been opened ? Is there a direct link from the door sensors or does it look for current flowing in the interior light circuit ? I've found that I have no bulbs in my B pillar interior lights, and I keep getting strange results when I try the bounce test. Yet, when I opened the boot, which does have a bulb, the suspension switched to soft mode, so, did the bulb current trigger the ECU to switch on the electrovalves.
As others have said the four passenger doors switches are all connected together and go to one input on the ECU and the boot has a seperate switch. Both inputs of the ECU connect directly between ground and the switches, and I would say that the ECU has an internal pullup resistor and isolation diode on both inputs - meaning that it doesn't rely on the interior bulbs to function.
I can hear both my electrovalves buzzing when I turn off the engine and close the doors. But, the front electrovalve stays in soft mode for say 10 mins. I wonder if the ECU thinks theres a door still open.
Yes definitely - 10 minutes is the timeout for when a door is detected to be open. If the doors are all closed the timeout is only 30 seconds.
Next step is to get some interior bulbs fitted and try again.
I think you'll find that the bulbs missing aren't the cause of the problem, and that you'll most likely discover when you replace them that they still don't work - due to a wiring or switch fault.

Regards,
Simon
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Post by Mandrake »

andmcit wrote:I'd say that's totally wrong by a long chalk - sounds like quite excessive
movement that could alter the cars' ride and handling - I don't get that
kind of movement on my normal SX equipped suspension estates and
certainly not my VSX saloons.

Can you determine if there is anything stamped or in fact printed onto
the new looking spheres David?
If its way too soft at the back, my money is on the wrong spheres being fitted to the rear struts - most likely it has "standard" spheres designed for a non-hydractive model fitted, which in combination with the centre sphere of a Hydractive2/Activa will make it way too soft and wallowy.

Check the part numbers on those spheres David, and report them here and we'll know for sure then.
One for Simon/Richard/Jim here - Is it possible that the metal discs that
are effectively the 'jets' of the hydractive spheres have been deliberately
removed from the centre sphere block on the rear? :shock:
It's possible, but highly unlikely, unless the person doing it was a real nutcase. :D Because the plugs that screw into the sides of the Hydractive block clamp down on the dampers (which themselves are about 10mm thick) there is nothing for that plug to screw down against to seal properly - except for the outer shoulder of the plug, so I think it's highly unlikely.

Much more likely that it just has the wrong spheres on the struts.

Regards,
Simon
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Post by Mandrake »

DickieG wrote:The rear end of an Activa does tend to feel rather soft and wallowy compared with other Hydractive Xantia's, I've looked into this issue in depth on mine, checking the Hydractive system electrically and hydraulically, sphere specification/pressure etc.

I wonder if it's a combination of Activa rear sphere's have a slightly larger damping hole (0.7) than standard Hydractive sphere's (0.6), the effect of having a very firm front end not allowing the body movement sensor to switch the system into firm mode as easily as standard Hydractive Xantia all leading to a feeling of imbalance.
Interesting point,

One which I wondered because when I ordered the rear strut spheres for my Hydractive 2 Xantia about a year ago, the spheres they actually supplied me were for the Activa (confirmed by the part numbers) and I queried this, and I just got a "thats all we can get" response from them. :roll: (oh the joys of living somewhere where Citroen's are rare and support is nearly non-existant...)

When I fitted those spheres I found the rear suspension just a little bit floaty and wallowy as you describe - nothing to be too concerned about, but not the rock stable gliding motion that I was used to.

But heres the kicker - despite the spec books saying that the Activa ones are 0.7mm and HA2 are 0.6mm, and confirming part numbers of the old and new spheres, they hole sizes are IDENTICAL, as measured very carefully with some precision drills.

What IS different is the thickness of the washer stack - the original spheres have four washers, the Activa ones have THREE washers. :?

Less total washer thickness means a lower opening threshold for the damping plates, and this will be what the difference is, not a tiny/non-existant difference in the hole size.

I thought for a long time about why they might have made the damping softer on the Activa spheres, and the only conclusion I could come to, and a flimsy one at that, is that it's to compensate for the increased frictional losses in the anti-roll ram, which would tend to add frictional damping of its own.

If you're concerned about it being a bit wallowy - I think it would be perfectly alright to fit a pair of Hydractive 2 rear strut spheres to an Activa, which will have the slightly increased damping thresholds, should get rid of that wallowing effect, but be prepared for the ride to be a bit harsher too...
Or could it simply be that in Citroëns' desire to produce the headline of a "No roll car" it meant that the front end has to be so stiff that the only way get an acceptable ride comfort was to make the rear extra soft so that it could effectively be "levered" by the front end (does that make sense?) otherwise customers would question "What's the point of it all"?
Hard to say really - the problem with the damping being firm at the front and soft at the rear (or vica versa) is that it tends to cause the car to pitch when you go over undulations, because the impulse response of the front and rear suspension are a lot different.

Having the damping response at the front and the rear the same causes the minimum amount of pitching over undulations - the car rises and falls almost vertically instead.

Regards,
Simon
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Post by DickieG »

Mandrake wrote:What IS different is the thickness of the washer stack - the original spheres have four washers, the Activa ones have THREE washers. :?

Less total washer thickness means a lower opening threshold for the damping plates, and this will be what the difference is, not a tiny/non-existant difference in the hole size.

I thought for a long time about why they might have made the damping softer on the Activa spheres, and the only conclusion I could come to, and a flimsy one at that, is that it's to compensate for the increased frictional losses in the anti-roll ram, which would tend to add frictional damping of its own.

If you're concerned about it being a bit wallowy - I think it would be perfectly alright to fit a pair of Hydractive 2 rear strut spheres to an Activa, which will have the slightly increased damping thresholds, should get rid of that wallowing effect, but be prepared for the ride to be a bit harsher too...
Interesting point there Simon, when I get time I'll swap some sphere's from my other Xantia's and see what happens to the ride.
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