Activa System: Working or Not?

Unread post by **CitroJim** » 02 Apr 2007, 20:56

Please bear with me, this is a very long post

Since I've had my Activa, I've had nagging doubts as to how well the Activa system is working and now I'm rapidly coming to a conclusion it is not quite as it should be

My suspicions are thus:

1. The car has a slight lean, more at the rear than the front, toward the nearside;

2. When the rear is up on axle stands, with the hydraulic system fully depressurised, the nearside rear wheel is cocked up very high, somewhere between low and normal suspension setting, whilst the offside rear wheel is right down, not far off the high setting. This can be explained by the Activa Ram being at full extension. It is very rigid and it is impossible to move the nearside wheel any further down or the offside wheel up. It is almost like the Activa Ram is stuck at full extension and cannot be moved.

I would have thought that with the hydraulics depressurised, the ram would move fairly easily. Maybe not. It is not seized arm bearings because the car responds to the height lever with all four wheels on the ground normally and when in soft mode I can push and pull the rear suspension nearly over its full travel by pushing on the boot. There are no creaks or other tell-tales that the rear arm bearings are badly worn.

3. If I repressurise the hydraulics with the suspension in low but still with the rear up in the air on stands, the front comes up when the lever is set to high but the rear will not move. The rear height corrector is clearly fooled by one wheel being up and the other down. I can only get the rear to move by jacking the rear enough to remove the axle stands and when I let the jack down, the rear bottoms out and then rises normally up to maximum height.

4. Now, with the car sitting on high, if I return the height lever to normal, the rear comes down to normal height (but leaning slightly) but the front stays at full height. The only way to get both front and rear to normal ride height is to go to low setting, allow both ends to fall and then move the lever to normal height. Both ends then come up to normal height.

Still with me

In normal use, the car sinks over to the nearside after standing the night and rapidly corrects itself to just a slight rear nearside lean on starting up.

This slight lean seems to me to be caused by the normal suspension cylinders "fighting" the Activa Ram.

The handling does not seem to be quite "right". That is all I can say and I came more to that conclusion after driving the TD Xantia this weekend for the first time in ages. It handled really nicely with little more roll than the Activa

Both hydractive electrovalves are fully functional and the anti-sink sphere is fairly recent. I cannot hear any life in the Activa electrovalve. Should it operate like the hydractive electrovalves and at the same time

Also, is it like a hydractive electrovalve that when off, the Activa system is in Hard Correction mode? (i.e. the Activa balancing sphere isolated)

When depressurised, should the Activa Rams move freely, like suspension cylinders will?

This evening, I started investigating. I can barely move the rear Activa Ram, even when jacking it or the wheels with the system depressurised. I tried to open the bleed nipple on the Activa Sphere block but no chance, It is a bit corroded and very tight and I bottled out. A sheared nipple here wild be a disaster

I then tried to "crack" the Activa Sphere but that defeated my tool. The cold wind and impending darkness then conspired against me.

I have read the print off the Activa section of the Citroen Technical Guide and I have a fair understanding of how it all works.

These I see as suspects:

1. Could the roll corrector be seized, thus holding the rams fully extended?

2. Could the Activa Sphere be totally flat (it looks old) and cause this?

3. Could the electrovalve be non-functional and holding the Activa system in maximum stiffness?

None of this, except perhaps a seized roll corrector, seems to explain though, why the ram seems immovable even with the system depressurised. Surely any residual pressure should leak away with the system depressurised?

Can the rams seize?

Thanks for staying with me

Strange stuff or am I chasing shadows and in fact this is all perfectly normal for an Activa

AndersDK · Unread post by **AndersDK** » 02 Apr 2007, 21:17

Not claiming to be a specialist on the Activa -

I do have a suggestion which always works from 1.st generation simple hyd Cits and up the range of elaborated systems :
Never, ever, have the wheels UN-loaded (free in air) when tracing a problem in the hydraulics.

1) The HC is always fooled.
2) Antisink system is always fooled
3) In hydractive systems differences in the rigidness is not to trace by any manual test this way either.
4) And the same goes for any standard or active antirollbar system (Activa).

To safely trace hydraulic problems in the suspension I always lift the offended axle wheels on to ramps (thats another story : I hate drive the car up the ramps).
This way you can safely mess around pushing HC or antiroll control valve rods observing the behaviour under the car, while the suspension is in normal loaded condition.
Also its much easier to interpret whats going on when the system is under normal load.
For tracing your activa system problem its not too bad either levering one side ramp with blocks to observe behaviour.

my pennies on the rear activa 'HC' ...

Unread post by **CitroJim** » 02 Apr 2007, 21:24

Anders,

Now what you have said makes perfect sense

Thank you for bringing some sanity to this

Like you I don't like driving up ramps and don't own any but I feel the time is rapidly approaching when I must.

It is moments like this that I realise I know nothing about Citroen Hydraulics, despite thinking that I do

LeeDJC · Unread post by **LeeDJC** » 02 Apr 2007, 21:39

I've got no idea with regard to the Activa's behaviour...sorry!

But a little tip for ramps to stop them sliding when you drive onto them, is to loop an old piece of carpet around the first "rung" of the ramp. That way the weight of the car will hold the ramp while you drive onto it

KevMayer · Unread post by **KevMayer** » 02 Apr 2007, 21:45

To depressurize the Activa rams you need to crack the accumulator to depressurize the rest of the system then, with the car on the ground, reach under the front wheel arch (at the rear of the front wheel) and pull/push the ends of the linkage arms of the roll corrector.

Do this a few times so that the car rocks from side to side 4 or 5 times.

I did this on my Activa and it depressurized enough for me to be able to take off my front ram (trying to seal the low pressure leak on the bleed pipe...again).

My Activa leaned a lot when I picked it up. The chap that sold it to me tried to disguize the lean by parking it outside his house with one wheel on the road, the other wheel on the pavement. When I got it home it was leaning so bad you would have fallen out if the door hadn't been closed. You can correct the lean by lifting the front onto ramps so the car is standing on its wheels, and not supported on axle stands, and getting underneath to adjust the two adjusters on the roll correction mechanism. I got my car to sit nice and level. It didn't lean again after I adjusted these. But, make sure you adjust each side by the same amount so you don't change the tension on the spring which connects to the roll corrector valve.

I did this some time ago and I had the engine running whilst I was underneath so that the system was at full pressure while I did the tweaks. It got a bit hot under there ...

And, the best way to test if the Activa system is working is to find a nice empty roundabout, late at night, and put your foot down as you go around it a few times. If the car rolls and feels like it's going to lose it, back off and you know you have a problem. If the car just slides sideways a little in a nice controlled way and doesn't lean much, then everything must be ok. I did this with my mate in the passenger seat and he was pinned to the door laughing his head off.

Damn it...i miss my Activa..

Cheers, Kev

DickieG · Unread post by **DickieG** » 02 Apr 2007, 22:07

In answer to point 1, I'm not quite sure what you mean unless the shell is twisted.

Point's 2 and 3; The roll corrector/high pressure part of the hydraulic system on an Activa is not depressurised until the bleed nipple on the rear block has been opened, (which you haven't done in fear of it snapping off, fair enough!). Consequently the rear ram is still pressurised and 'stiff'. When I was replacing the bottom bush on the rear ram on mine I found that the ram would extend/retract almost at will and was a bit of a swine to get to line up with the bracket on the anti-roll bar when I refitted it, almost as if it had a mind of it's own. I hadn't de-pressurised the Activa system as I wasn't aware of the above at the time.

4, Appears to be a stiff height corrector issue.

The lean to the nearside when parked is a common Activa 'quirk'. As long as it corrects itself when the engine is started I wouldn't worry too much (I don't with mine when it does it

), this MAY possibly be sorted out by spending MANY hours (yes I have) by carrying out the following operations below.

As far as "The normal suspension cylinders fighting the Activa rams" I think that what you may have here is a roll corrector linkage which has a degree of what I can best describe as "Wind-up" combined with possibly wear in the guide blocks just prior to the rods bolting onto the wishbones.

Part of setting up an Activa correctly involves loosening the securing bolts on the wishbones in order to release that "Wind-up".

It is also important the roll corrector linkage is centralised in the connecting bracket assembly (where the rods connect onto the roll corrector under the centre of the car) and that ANY adjustments made to the threaded rods are even on each side.

Another important point is that the connecting ball joint's (where the linkage turns 90 degrees to connect to the wishbones) are not 'twisted'.

What you can do to check that the system works is to get the car up on ramps (at normal height) then push/pull the roll corrector linkage from side to side which should cause it to operate and 'correct' the induced roll.

If at the end of all this the car is leaning to one side when the engine is running, you can adjust the linkage close to the roll corrector (that will keep you amused for hours, day, after day, after day, after day, if like me you seek perfection

which may explain why Citroen allow a tolerance of about 5mm each side IIRC.

I learned the above from a rather useful Citroen Training video I have.

To be honest I do wonder whether Activa's are worth it unless you thrash around bends all day long. I find that I drive mine much quicker than I would any other car of mine just to see that the system works!

Xaccers · Unread post by **Xaccers** » 02 Apr 2007, 22:10

Jim, if you like, I will see if we can get access to the Finmere airsoft site on Friday, as it used to be an airbase and has the remains of an inspection bay (actually, just the ramps, the surrounding building was removed long ago).
Had my car up on them on Saturday to check everything underneath while I changed the LHM for hydraflush.
Going to use them again to change the rear spheres

DickieG · Unread post by **DickieG** » 02 Apr 2007, 22:18

When it comes to testing the Activa anti-roll system whilst driving, you need to bear in mind that there are a couple of features to the system.

The first is that on a quick input of steering (such as a mini roundabout/swerve) there is NO roll correction, all that happens is that the very stiff (28mm) anti-roll bars are made 'solid' by the Activa system.

The second feature to the system is that should the roll continue for a period of time (I can't exactly recall off hand) THEN the rams come into play to correct the roll.

KevMayer · Unread post by **KevMayer** » 02 Apr 2007, 22:22

I see..... but it's much more fun to push it around a roundabout.

Unread post by **CitroJim** » 03 Apr 2007, 12:47

Thanks all, very much appreciated. Looks as if I have been looking under the wroung end of the car for this problem and getting myself well and truely confused in the process, especially with unloaded wheels.

I shall stop using axle stands and invest in some decent ramps and then have a good look at the HC and RC along with the RC linkages.

Richard, thanks for the info on the RC linkages winding up. It cetrainly looks like the front HC is a bit stuck so chances are the RC is not entirely happy either. I've not looked closely in that area but I do know it is very, very dry around there, unlike our TD which is soaking in old LHM and oil in that area. My Activa stood for a long while before I acquired it and it really shows in some areas.

To be honest I do wonder whether Activa's are worth it unless you thrash around bends all day long. I find that I drive mine much quicker than I would any other car of mine just to see that the system works!

I do that and that is what has led me to this post! It's worth it for the grin factor and perhaps more so, the technical challenge of sorting it out and maintaining it.

And, the best way to test if the Activa system is working is to find a nice empty roundabout, late at night, and put your foot down as you go around it a few times. If the car rolls and feels like it's going to lose it, back off and you know you have a problem. If the car just slides sideways a little in a nice controlled way and doesn't lean much, then everything must be ok. I did this with my mate in the passenger seat and he was pinned to the door laughing his head off.

Kev, I like your test procedure

So far, I have yet to find a roundabout quiet enough to indulge in such fun, even in Milton Keynes, the home of the roundabout

I must say it is great on the twisty stuff though. I regularly take a trip along a very winding unclassified road with some tight bends and adverse camber. With the hydractive in sport mode I can move along at quite astonishing speeds, faster than I can in the 205GTi.

I shall report back after a few more checks

jeremy · Unread post by **jeremy** » 03 Apr 2007, 14:10

I think the Citroen workshop manual for the Activa system can be downloaded here (in english)

Loads of other useful stuff as well

http://citroeny.cz/servis/servis.htm

Unread post by **CitroJim** » 03 Apr 2007, 23:02

jeremy wrote:I think the Citroen workshop manual for the Activa system can be downloaded here (in english)

Loads of other useful stuff as well

http://citroeny.cz/servis/servis.htm

Thanks Jeremy, some very useful stuff there 8)

An update. I had a quick look at the Roll Corrector this evening. Only a quick one as I had to be somewhere. I tried pulling and pushing the Roll Corrector linkages and initially it would only tilt to one side. After some more tugging it started to tilt both ways

So, a partially seized Roll Corrector or linkages.

A trip out confirmed this has made a big difference in that it is cornering a lot "flatter" now and feels a lot more "planted"

I'm happy again!

It just remains to have a cood look at the Roll Corrector and front Height Corrector later in the week.

XantiaMan · Unread post by **XantiaMan** » 21 Jul 2009, 11:52

DickieG wrote:When it comes to testing the Activa anti-roll system whilst driving, you need to bear in mind that there are a couple of features to the system.

The first is that on a quick input of steering (such as a mini roundabout/swerve) there is NO roll correction, all that happens is that the very stiff (28mm) anti-roll bars are made 'solid' by the Activa system.

The second feature to the system is that should the roll continue for a period of time (I can't exactly recall off hand) THEN the rams come into play to correct the roll.

This is very useful information, do you recall where you obtained it from?

If i try to test the system it always seems to roll to some degree but more so at low speeds. I have noticed this more if the steering is rocked quickly whilst driving in a straight line.

But, go a bit faster, or drive more briskly and it soon cuts in, especially on long sweeping corners.

I have come to the conclusion that the system really is very clever and with inputs from the steering and the actual speed of the car together with other factors it decides if and how much it should correct roll.

Sl4yer · Unread post by **Sl4yer** » 21 Jul 2009, 21:24

The technical info is in the Citroen Guide, available here. It's quite complicated to mere mortals such as myself. One thing which is clear (from the guide and the Lexia) is that the various sensors only control the switching on or off of the anti-roll system. Once engaged, it is purely hydraulically operated. (Early reviews of various computers 'fighting' each other is nonsense as far as I can see).

The system relies on correct sphere pressures, and free movement in the roll corrector, it's linkages and control arms. I've yet to see how the steering angle sensor fault affects the system on the Lexia, because mine doesn't seem to throw one up very often!

James

DickieG · Unread post by **DickieG** » 21 Jul 2009, 21:30

XantiaMan583 wrote:
DickieG wrote:When it comes to testing the Activa anti-roll system whilst driving, you need to bear in mind that there are a couple of features to the system.

The first is that on a quick input of steering (such as a mini roundabout/swerve) there is NO roll correction, all that happens is that the very stiff (28mm) anti-roll bars are made 'solid' by the Activa system.

The second feature to the system is that should the roll continue for a period of time (I can't exactly recall off hand) THEN the rams come into play to correct the roll.
This is very useful information, do you recall where you obtained it from?

I have quite a collection of Citroën workshop manuals, training manuals, training video's, launch sales press kits etc