'Limp' nearside rear corner?

Unread post by **Dommo** » 05 Jun 2010, 12:52

I've just measured the distances between the centre of the wheel and the wheel arches, and on the front the distance is near enough identical +/- a few mms. The rear however... The nearside is a whole 5.5-6 CM (!!) lower than the offside!

Could it be that someones fitted the wrong rear shock/strut to the car at some point? Or it's just broken??

KevMayer · Unread post by **KevMayer** » 06 Jun 2010, 10:55

Just to confirm.. was the Activa on a flat surface?

On my driveway, sometimes I park the Activa in a place where the front wheels are on the level horizontally but the rear wheels are on a slope where the driveway on the right is about 4 inches lower than on the left. This means my left rear wheel sinks up into the wheel arch and there is a large gap above the right rear wheel.

Could you be seeing this effect?

Unread post by **CitroJim** » 06 Jun 2010, 11:40

KevMayer wrote: Could you be seeing this effect?

Good point Kev, It's caught me out in the past.

That's why an Activa can be a 'mare to level

A perfectly elvel surface is essential.

Dom, If this effect is seen on a known good surface then I honestly have no idea

Unread post by **Dommo** » 06 Jun 2010, 22:07

Thanks for the replies chaps.

My drive is sloped, but unfortunatly my Activa has these same symptoms whether the car is facing up or down the drive, and also on the flat. I went to Aldi on friday and it's a level car park, and it's very noticable that the car is leaning at the rear towards the nearside (lower on the nearside)

Me and my dad had a look under the car yesterday, it does look as though the nearside strut (what the corner sphere attaches to) is cleaner (and newer?) than the offside one. Could it be the wrong strut? Is there such thing as a wrong strut that could cause this effect?

If so, does anyone have a nearside rear strut for an Activa?

Thanks!

Unread post by **Dommo** » 11 Jun 2010, 08:41

Any ideas folks? It would appear that all rear corner spheres have the same volume of gas, suggesting all rear cylinders also have the same volume/stroke, so does that mean my potentially new cylinder can't be wrong? What's different about the different cylinders?
Thanks. Sorry about all the questions

KevMayer · Unread post by **KevMayer** » 11 Jun 2010, 20:23

An idea... because I've just done the offside rear arm bearing replacement job and I depressurised the Activa system to make it easier to move the rear ram out of the way. Since putting it all back together It looks like I may have something similar to what you describe in that the rear end seems to be lower at the offside. This could be because some air may have got into the Activa system. But I've not used the Activa much since the bearing job so, I'm hoping that a bit of spirited cornering may sort it out.

Anyway, this is my theory...

I think I remember that you've had your rear ram off recently. Either that or the front ram. So, after replacing it could there be air trapped in the anti roll system which is upsetting the action of the rams.

In each ram the small side of the piston (shaft side of piston) is supplied with direct pressure from the common hydraulic system. The large face of each piston (non shaft side of piston) is pressurised from the sealed hydraulics which have the Activa sphere/electrovalve. This sealed side is fed or drained by the roll corrector.

If you have air trapped in the sealed side then could this be giving you these symptons.

I'm not sure how you'd bleed this air out.

EDIT: Just been out to measure my Activa with it parked on a level drive and the rear left wheel arch is half an inch higher than the rear right wheel arch.

Unread post by **Dommo** » 11 Jun 2010, 20:53

I wondered if the anti roll system could cause these issues, but I'm pretty sure it isn't - the system certain gets a pasting most times I drive the car

What are the symptoms of flat/low pressure activa ram spheres?

Also, it was the front ram we replaced. We changed the rear ram bush and sealed the leakage return spigot with the ram in place. And the difference in ride height is quite large, 5-6 cms.

Thanks for the input Kev, I wish I could get to the bottom of this cars issues...

Unread post by **CitroJim** » 11 Jun 2010, 21:11

Dom, this problem has me a bit baffled. Except for one possibility....

The Activa system could cause it if the front and rear rams are working out of phase with each other. You had the front ram off. Are you 100% sure the pipes are back on correctly and what looks right is wrong.

Thi si the correct way (quote from my website)

Replacemnt is a reversal of removal but note that the long flexi pipe must be fitted to the front union on the ram as you look at it in its fitted position. The long pipe must connect to the right-hand (as you look at it) rigid pipe.

I'm not saying that's it but worth a check. I don't think there is a problem with the rear cylinders unless one has a broken pushrod and you'd know about that. DickieG can show and tell the result of a broken pushrod. Generally, if there's no leaks, the cylinders can be thought ton be OK. Also if the car is level on service high they can be assumed OK.

Dommo wrote: What are the symptoms of flat/low pressure activa ram spheres?

A flat Activa Balancing sphere will make the ride rick-hard as there is no "spring" between the two bars and effectively they become two girders. The system will effectively be in permanent maximum roll correction and will force the anti-roll bars to lock solid.

A flat Activa Accumulator will cause the car to do the "traffic Light" shuffle" in time with the pressure regulator cutting in and out.

When you say you sealed the rear ram leakage return spigot I presume you cured a leak and did not block it off totally. If you did, leakage will have a heck of a job escaping and may possibly hold the ram in an incorrect position. Mind you, I'd have thought it would have leaked from somewhere else before causing that.

It's all a bit of a mystery....

The new ram bush is not so tight that it's interfering with the free movement of the ram is it?

We'll get there...

Unread post by **CitroJim** » 11 Jun 2010, 21:18

Sorry Kev, just seen your thoughtful post after posting mine

That is a very good point...

KevMayer wrote: I'm not sure how you'd bleed this air out.

In my experience, having been all over it like a rash, the Activa system is pretty much self-bleeding and a few bouts of Citarobics will do the trick. There is a bleed nipple on the Activa sphere block at the rear but this is more for depressurising the Activa system before work rather than bleeding it afterward.

More often than not, it's seized anyway...

You can see it in the fourth picture down on this page

Unread post by **Dommo** » 12 Jun 2010, 16:22

CitroJim wrote:Dom, this problem has me a bit baffled. Except for one possibility....

The Activa system could cause it if the front and rear rams are working out of phase with each other. You had the front ram off. Are you 100% sure the pipes are back on correctly and what looks right is wrong.

Thi si the correct way (quote from my website)

Replacemnt is a reversal of removal but note that the long flexi pipe must be fitted to the front union on the ram as you look at it in its fitted position. The long pipe must connect to the right-hand (as you look at it) rigid pipe.
I'm not saying that's it but worth a check. I don't think there is a problem with the rear cylinders unless one has a broken pushrod and you'd know about that. DickieG can show and tell the result of a broken pushrod. Generally, if there's no leaks, the cylinders can be thought ton be OK. Also if the car is level on service high they can be assumed OK.

Dommo wrote: What are the symptoms of flat/low pressure activa ram spheres?
A flat Activa Balancing sphere will make the ride rick-hard as there is no "spring" between the two bars and effectively they become two girders. The system will effectively be in permanent maximum roll correction and will force the anti-roll bars to lock solid.

A flat Activa Accumulator will cause the car to do the "traffic Light" shuffle" in time with the pressure regulator cutting in and out.

When you say you sealed the rear ram leakage return spigot I presume you cured a leak and did not block it off totally. If you did, leakage will have a heck of a job escaping and may possibly hold the ram in an incorrect position. Mind you, I'd have thought it would have leaked from somewhere else before causing that.

It's all a bit of a mystery....

The new ram bush is not so tight that it's interfering with the free movement of the ram is it?

We'll get there...

Hi Jim. Thanks for the extensive response. I think we have it plumbed in correctly, my rams work in opposite ways when you push/pull on the roll correction linkage - ie the rear one extends when the front contracts, and the rear one contracts when the front extends, which I assume is correct seeing as the rams are on opposite corners? I will check the plumbing if you think it could be an issue. Do your rams work in the same way? And how would the car handle if the rams were working against eachother?

I thought that would be the case regarding the rear cylinders, however my rear end isn't level when on service high, I can't remember how much less it was on service high but it was definately lower on the nearside. I'll measure it in a minute as we're about to try and get the accumulator sphere off again with our home-made sphere tool - that keeps breaking

And regarding the leakage return spigot, we used some sealant (can't remember what exactly) and a cable tie to tighten the seal between the spigot and return pipe.

I think the rear bush is alright, but it's a good idea you've thrown up, it doesn't seem to be an issue, and it's made from a self lubricating material so it should be ok I'd imagine?

CitroJim wrote:Sorry Kev, just seen your thoughtful post after posting mine

That is a very good point...

KevMayer wrote: I'm not sure how you'd bleed this air out.
In my experience, having been all over it like a rash, the Activa system is pretty much self-bleeding and a few bouts of Citarobics will do the trick. There is a bleed nipple on the Activa sphere block at the rear but this is more for depressurising the Activa system before work rather than bleeding it afterward.

More often than not, it's seized anyway...

You can see it in the fourth picture down on this page

I had seen the bleed nipple on the Activa sphere block, and assumed like you say, that it is to depressurise the Activa system. I've noticed that the car won't sink when trying to get the car to go to service low from service high when the front is up on axle stands, and I assume it's because of the Activa system being pressurised as when you turn the engine off it will sink, eventually. A slanted driveway doesn't help though.

Thanks. Dom

KevMayer · Unread post by **KevMayer** » 13 Jun 2010, 16:26

The fact that the rear doesn't sink to service low may indicate the area where the problem is.

The Activa system works independantly to the rest of the suspension in that it's an addition to a hydractive2 system. The height of each end should go up and down to service high and low as commanded. All the Activa system does is to control how much the Xantia leans from side to side.

The Activa system shouldn't hold the rear end up. It should just cause it to lean. The rear height corrector may be sticking.

Unread post by **Dommo** » 13 Jun 2010, 16:32

No sorry I didn't explain it very well. It does sink, however when the front is on stands and the rear wheels are chocked because of my wonky sloped drive it takes quite a while to sink, because of the trailing arm layout presumably - if it's not the activa system?

The only reason I wondered whether the Activa system could affect it is due to the sloping drive making the roll correction linkage think the car is constantly rolling to one side?

Unread post by **CitroJim** » 13 Jun 2010, 20:50

I find that if the car is level, the rear end rises and falls at the expected speed. However, if the front is up on stands, the rear is most reluctant to fall and this applies, I find, to all Xantias. I often have to "help" them down by sitting in the boot

Absolutely Kev, the Activa system will have no influence on this as effectively they are droplinks.

Dom, if the front wheels are not on a level surface, then yes, the Activa system will try to correct the level and tilt it.

Have you tested yet on a known level surface?

Having said that though, on service high, even on a sloping surface, the gaps between wheels and wheelarches should be substantially level.

How does the car feel when driving? does it feel level and handle properly.

Bring it to the National Rally and let us have a look at it....

I reckon now it needs an experienced eye cast over it whilst stood next to a known good example.

Unread post by **Dommo** » 13 Jun 2010, 21:41

Hi Jim.

Is this the National Rally you mentioned?

http://www.nationalroadrally.co.uk/2010/index.php

If so I won't be able to make it, my final university exam is on the 5th July so I'll need to be doing a lot of revising that week!

I had noticed that helping the car lower at the back seems to work, the sitting in the boot idea seemed to work well enough but I wasn't sure whether this was the norm, so I guess it is! I just wondered whether it was the Activa system saying no and keeping the rear end in the air but obviously not.

My drive is on the wonk both side to side and front to back so the nearside front is at the lowest point, but I've tried pointing the car both up and down the drive so nearside front is at the highest point too, and both times the nearside rear is quite far into it's travel. I even noticed it at my local Aldi car park which is near enough flat, I'd parked up, noticed it was leaning to the nearside at the rear, and sure enough when I came out 15 minutes later it was still leaning. I've got some photos of the rear wheels on service high and service low with a tape measure against them that I'll post up shortly.

It handles well enough to me, but I've not drive another Activa to be able to comment. The car does seem to be quite bouncy when the anti roll system is tight, around 90 degree corners on bumpy country lanes for example, the car will bounce - whicih makes me think the Activa balancing spheres need replacing relatively soon. But if the rear end is leaning to one side, and the engine continues being awful on fuel, I can't really afford new spheres, until my degree is done anyway..

Thanks for the response Jim, I'll get those pictures up shortly.

Unread post by **Dommo** » 14 Jun 2010, 00:03

Shortly he says...

Nearside rear on service high:

Offside rear on service high:

Nearside rear on service low:

Offside rear on service low:

And here is the car from a distance, sorry about the different camera angles, but you can see the normal ride height of the nearside rear is significantly lower than it should be:

And the offside: