CURIOUS SUSPENSION

FEDAK · Post by **FEDAK** » 03 Mar 2003, 17:43

WHILST SITTING AT SOME TRAFFIC LIGHTS IN MY 1.9 TDLX XANTIA WITH MY FOOT ON THE BRAKE PEDAL. THE REAR OF THE CAR RAISED ITS SELF UP OF ITS OWN ACCORD THEN SETTLED ONCE I STARTED MOVING. AT A SECOND SET OF LIGHTS THE FRONT OF THE CAR DID THE SAME. I BLED THE BRAKES AT THE WEEKEND TO TRY AND IMPROVE THE FIRMNESS OF THE BRAKE PEDAL (SEE BRAKE PROBLEMS). TO NO AVAIL. NOT SURE WHATS GOING ON IS MY CAR POSESSED ??

AndersDK · Post by **AndersDK** » 04 Mar 2003, 03:24

- eeerrh
Since the Xantia has several different suspension systems - according to exact model/year - we need to know the exact type/model you have to shoot on your problem [:I]
XM & Xantia can be quite complicated to faulttrace in the hydraulic system - because of the many (& various) components fitted.
try download tech document found here :
http://www.tramontana.co.hu/citroen/guide.html
[^]

FEDAK · Post by **FEDAK** » 04 Mar 2003, 13:18

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by AndersDK

- eeerrh
Since the Xantia has several different suspension systems - according to exact model/year - we need to know the exact type/model you have to shoot on your problem [:I]
XM & Xantia can be quite complicated to faulttrace in the hydraulic system - because of the many (& various) components fitted.
try download tech document found here :
http://www.tramontana.co.hu/citroen/guide.html
[^]
<hr height="1" noshade id="quote"></blockquote id="quote">
1997 1.9 tdlx xantia

mbunting · Post by **mbunting** » 04 Mar 2003, 22:01

I thought they did this all the time ( rear only ). Something to do with the back brakes and the suspension being the same circuit.
Sure I've read that on here somewhere.
Mine does it, and has done since I got it. Not worried at all.

Homer · Post by **Homer** » 04 Mar 2003, 23:54

You could try using your handbrake?

maxrobertson · Post by **maxrobertson** » 15 Apr 2003, 21:25

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Homer

You could try using your handbrake?
<hr height="1" noshade id="quote"></blockquote id="quote">
I agree. As a "White Van Man" night shift driver one gets pretty pissed off with other drivers sitting with their foot on the brake pedal!!

Fox · Post by **Fox** » 15 Apr 2003, 22:09

Doesn't this happen when the anti sink sphere needs changing?

jeremy · Post by **jeremy** » 15 Apr 2003, 22:39

Is the car on the level or on a slight incline when this happens. If it is on an incline the suspension will adjust itself to reflect the differing loads on the front and rear wheels and what you are noticing is a sign the systemis working properly. If with the car parked on level ground with the handbrake applied you move the height control to maximum and then stand beside the car while it rises you will see that the back wheels roll forward a bit due to the trailing arm rear suspension. This will happen to a lesser extent when the car levels and if you have the brakes applied some of the movement will be absorbed by the suspension and when you let the brakes of the rear suspension will appear to jump.
My understanding of the anti-sink mechanism is that the heart of the system is the valve which does the work and the sphere is to ensure there is always some pressure available for the back brakes, wspwcially on moving off after a long stop - ie during the period us with older cars would be waiting for the suspension to pump up. There was a good description of the system a couple of weeks ago.
jeremy

JohnD · Post by **JohnD** » 16 Apr 2003, 00:36

My Xantia 2.1 has done this since it was new, particularly if, as Jeremy says, it's slightly off level. Does it even more if you brake hard at traffic lights. You probably haven't anything to worry about.

xactiva · Post by **xactiva** » 16 Apr 2003, 01:33

I think this is true of all the hydropneumatic ciroens.
What happens is, as you brake, the hydraulics pressurise the front suspension in order to keep the level correct (the anti-dive characteristic of our cars).
Once you have stopped, the system does a bit of a rejig to balance itself out again. usually if you release the brake pedal or after a short amount of time.
It can also happen if you corner hard, then stop. mind you mine is an activa which has more gubbins working sideways to correct body roll, so I guess yours doesn't do the last bit!

alexx · Post by **alexx** » 16 Apr 2003, 17:38

There are some misunderstandings about height correctors and 'anti dive function', so I'll try to explain.
Height correctors are not meant to implement anti-dive. They are designed ONLY to set the car on the correct height, no matter how many persons are in the car, and to interfere during the drive as little as possible. So they have internal damping and react slowly, after a few seconds.
On the other side, anti-dive function is implemented in every car. If you look at the front arm, you will see that its axis is not horizontal, but is slightly angled. On GS and BX, this angle is higher, so front end dives very little even during heavy braking, and height correctors rarely gets triggered. On Xantia and XM, this angle is lower, and front end dives more (to improve braking ability, I suppose), so height corrector get's triggered sometimes. On XM, this 'anti-dive angle' is 4 degree on cars not equipped with HA, and (only) 1 degree on HA equipped cars.
'Anti-rise effect' on the rear is achieved in similar fashion. If rear end rises too much during braking, it means that braking force of rear brakes is too low.

algieuk · Post by **algieuk** » 18 Apr 2003, 14:29

As for the brake pedal sogginess, remove the spring from the pedal discussed elsewhere on the forum (5 minute job). It is a truly miracle cure