Rear end sinks when engine not running

This is the Forum for all your Citroen Technical Questions, Problems or Advice.

Moderator: RichardW

Post Reply
Stempy
Posts: 1626
Joined: 26 Feb 2004, 23:21
Location: Cloud Cuckooland
My Cars: C5 V6 Mk1 assainated by wife
Renault Kangoo 1.6 auto, tarted up and remapped
Still missing the Xantia V6
Not missing the AX
Contact:

Rear end sinks when engine not running

Post by Stempy »

Even when on max height the rear end of the Xant sinks within a few minutes of switching the engine off. It's had a rear accumulator within the last year, could I be looking at replacing the anti sink valve? It stays where its put all the time the engine is running and the dog bone seems ok.
It infuriates me to be wrong when I know I'm right

Lexia ponce

http://perception.dyndns.biz/~avengineering/index.htm
User avatar
Old-Guy
Posts: 1798
Joined: 11 Sep 2008, 12:08
Location: Gloucestershire
My Cars: 2011 Grand C4 Picasso VTR+ 1.6HDi in Kyanos Blue
1995 Xantia Estate SX 1.9TD in Vert Vega "The Green Lady" - now owned by XanTom
1998 Xantia 2.1 VXD Estate in Mauritius Blue - R.I.P. (terminal tin-worm)
x 17

Post by Old-Guy »

It does sound as though it's the anti-sink valve, but the Anti-Sink Spere (a.k.a. Rear Accumulator) plays a vital part by providing pressure to ensure that the ASV closes properly, especially when the car is lightly loaded. An alternative could be that one of the rear rams is leaking back to the reservoir excessively.

As it's such an easy job, if you haven't done it already, I'd bleed the rear brakes to flush out any old fluid and dirt lurking in the rear brake lines that might be causing problems - especially if there's any gas/air in the rear system which could be pushing the same bit of crud back to jam the ASV partly open. Of course the ASV could simply be stuck open as it only closes when the engine stops and re-opens when the STOP warning goes out.

As you'll see from the Anti-sink Suspension section of The Citroën Technical Guide the rear suspension and rear brakes are intimately linked by the rear hydraulics. The Guide may help you work out where the problem lies.
2011 Grand C4 Picasso VTR+ 1.6HDi in Kyanos Blue
1995 Xantia Estate SX 1.9TD in Vert Vega "The Green Lady" - after 11 years now owned by XanTom
1998 Xantia 2.1 VXD Estate in Mauritius Blue - R.I.P. (terminal tin-worm)
User avatar
Xaccers
Posts: 7654
Joined: 07 Feb 2007, 23:46
Location: Milling around Milton Keynes
My Cars:
x 184

Post by Xaccers »

All the rear spheres play a roll in keeping the anti sink valve closed, if some are low then the valve won't shut and the back sinks.
If your car has hydractive but is soft when running then it is likely the firmer corner spheres need replacing.

The a/s sphere is there to provide brake pressure when the pump is not running as the closed a/s valve isolates the rear from the front accumulator sphere.
Without it if your aux belt snapped you'd have no rear brakes.
1.9TD+ SX Xantia Estate (Cassy) running on 100% veg
1.9TD SX Xantia Hatchback (Jenny) running on 100% veg for sale
Laguna II 2.0dCi Privilege (Monty)

DIY sphere tool
niva44
Posts: 3
Joined: 05 Sep 2010, 16:21
Location:
My Cars:

rear end sinks

Post by niva44 »

I had the same problem with my XM after the spheres were replaced, I opened the bleed valve half a turn to release any air, I heard the air hissing out in less than 2 seconds ,re-tightened the valve and the problem has been solved.
User avatar
Old-Guy
Posts: 1798
Joined: 11 Sep 2008, 12:08
Location: Gloucestershire
My Cars: 2011 Grand C4 Picasso VTR+ 1.6HDi in Kyanos Blue
1995 Xantia Estate SX 1.9TD in Vert Vega "The Green Lady" - now owned by XanTom
1998 Xantia 2.1 VXD Estate in Mauritius Blue - R.I.P. (terminal tin-worm)
x 17

Post by Old-Guy »

Good point! I took it as read that whoever changed the A/S sphere knew what they were doing and thoroughly bled the rear brakes as part of the job - absolutely essential and very easy.
2011 Grand C4 Picasso VTR+ 1.6HDi in Kyanos Blue
1995 Xantia Estate SX 1.9TD in Vert Vega "The Green Lady" - after 11 years now owned by XanTom
1998 Xantia 2.1 VXD Estate in Mauritius Blue - R.I.P. (terminal tin-worm)
Stempy
Posts: 1626
Joined: 26 Feb 2004, 23:21
Location: Cloud Cuckooland
My Cars: C5 V6 Mk1 assainated by wife
Renault Kangoo 1.6 auto, tarted up and remapped
Still missing the Xantia V6
Not missing the AX
Contact:

Post by Stempy »

These are very valid points as when I think about it the problems began when I changed the rear electrovalve so I bet it's just trapped air, although I did bleed the brakes at the time I was in a hurry and probably didn't do a very thorough job. As for knowing what I'm doing, well 99% of my life is guesswork, the other 1% I just make up as I go along........
It infuriates me to be wrong when I know I'm right

Lexia ponce

http://perception.dyndns.biz/~avengineering/index.htm
Post Reply