Anti Sink Query

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

Moderator: RichardW

davehughes
Posts: 76
Joined: 26 Dec 2005, 13:50

Anti Sink Query

Post by davehughes » 22 Jan 2006, 19:26

What year/reg did the Xantias get anti sink fitted. I saw a parked M reg (year newer than mine) several times over two hours today and it didn't sink.

User avatar
Mandrake
Posts: 7790
Joined: 10 Apr 2005, 17:23
x 194

Re: Anti Sink Query

Post by Mandrake » 22 Jan 2006, 20:12

davehughes wrote:What year/reg did the Xantias get anti sink fitted. I saw a parked M reg (year newer than mine) several times over two hours today and it didn't sink.
Citroen manuals say it was introduced in production in December 1993 which seems to equate to cars beginning to be sold around mid 1994.

Yep, 2 hours is nothing for anti-sink 8) My car hasn't dropped even slightly when I return to it 8 hours later after finishing work...

Regards,
Simon

Peter.N.
Moderating Team
Posts: 9251
Joined: 02 Apr 2005, 16:11
x 182

Post by Peter.N. » 22 Jan 2006, 20:26

Mind you, some of those without anti sink, dont sink!

davehughes
Posts: 76
Joined: 26 Dec 2005, 13:50

Post by davehughes » 22 Jan 2006, 20:28

Mine sinks within the hour, why do they vary? :?

User avatar
Mandrake
Posts: 7790
Joined: 10 Apr 2005, 17:23
x 194

Post by Mandrake » 22 Jan 2006, 22:40

Well my mums 1993 1.9TD without anti-sink usually goes down completely in under an hour...and it has good spheres on it including a new accumulator.

Regards,
Simon

User avatar
CitroJim
A very naughty boy
Posts: 41564
Joined: 30 Apr 2005, 23:33
x 1032

Post by CitroJim » 22 Jan 2006, 22:46

Mandrake wrote:Well my mums 1993 1.9TD without anti-sink usually goes down completely in under an hour...and it has good spheres on it including a new accumulator.

Regards,
Simon
Yep, that is about the score with mine. I guess it's all down to how leaky (in the sense of seepage internally within the hydraulic components rather than the spots of LHM on the drive type of leak) the overall system is and a well used one like mine is bound not to be 100%. Any idea how long a non-anti-sink would stay up when brand new?

User avatar
AndersDK
Posts: 6060
Joined: 21 Feb 2003, 05:56
x 1

Post by AndersDK » 22 Jan 2006, 23:35

My BX turbo Estate slams down on rear within 3-5 minutes. New spheres, new acc, no strange symptoms from the hydraulic system and brakes are fine.
Its on hydracleanse right now.

davehughes
Posts: 76
Joined: 26 Dec 2005, 13:50

Post by davehughes » 22 Jan 2006, 23:59

my front end does that

User avatar
Mandrake
Posts: 7790
Joined: 10 Apr 2005, 17:23
x 194

Post by Mandrake » 23 Jan 2006, 00:09

3-5 minutes is abnormally fast indicating an actual fault condition.

For the front it could be the struts or the front height corrector.

For the rear it could be the brake control valve or the rear height corrector.

From new I think they still only stayed up for 2-3 hours maximum, I remember my GS used to stay up for about 2 hours at the front as well...

The main sources of leakage in an "old" car are the brake control valves and height correctors. The suspension cylinders/struts dont usually leak much unless they're faulty.

This is why the anti-sink system works so well - it only blocks leakage via the height correctors and brake control valve, it can do nothing to block leakage of the suspension cylinders themselves, and yet an anti-sink car can still stay up for days. (Showing that the leakage from the cylinders is very low)

It can also be affected by the oil quality, I've often noticed that fresh new LHM reduces the leakage rate compared to old dirty oil...

I read somewhere that this is due to the breakdown of the molecules of the oil with age and use causing a thining effect (and perhaps reduction in surface tension?) allowing the oil to migrate through the fine gaps in the system more easily. (Such as past the height corrector control shafts) I don't know how true this is though.

Regards,
Simon
Last edited by Mandrake on 23 Jan 2006, 00:16, edited 1 time in total.

Peter.N.
Moderating Team
Posts: 9251
Joined: 02 Apr 2005, 16:11
x 182

Post by Peter.N. » 23 Jan 2006, 00:14

Out of three CXs and three BXs, I have had one or two that stay up all night! I think as mentioned, its all to do with the general condition of the hydraulics, primaraly the struts/cylinders and height control valves, and in the case of the rear, the brake valve.

jgra1
Posts: 4399
Joined: 27 Nov 2005, 20:07
x 15

Post by jgra1 » 23 Jan 2006, 01:45

my 94 TD just doesn't sink... (hasn't got anti sink fitted)

?

otherwise all fine, front spheres are new, back ones need changing.

FrenchLeave
Posts: 359
Joined: 18 Jan 2005, 22:47

Post by FrenchLeave » 24 Jan 2006, 18:55

My XM with anti sink has stayed up for 10 days without noticeable sinking. As Mandrake said, the a/s valves limit the leakage to the suspension cylinders. When my car did develop the habit of dropping its rear end in minutes (useful for loading the shopping) it was caused by a massive internal leak in one of the rear suspension cylinders.

Derek

Homer
Posts: 1497
Joined: 26 Feb 2003, 11:52
x 12

Post by Homer » 25 Jan 2006, 09:06

AndersDK wrote:My BX turbo Estate slams down on rear within 3-5 minutes. New spheres, new acc, no strange symptoms from the hydraulic system and brakes are fine.
Its on hydracleanse right now.
Surely the accumulator would provide enough pressure to keep it up for more than 5 mins.

If the seepage is that bad when it's stood it can only be worse when it's moving.

My BXs could go overnight on a cold day without sinking, on a really warm day they could be down after a couple of hours. I have experience of the GS, BX and Xantia and none have ever sunk that fast.

User avatar
AndersDK
Posts: 6060
Joined: 21 Feb 2003, 05:56
x 1

Post by AndersDK » 25 Jan 2006, 12:26

Naah Homer -

There are absolutely no symptoms from hydraulics during drive. Normal tick interval (app 1minute) - perfect brakes.
Funny - this morning it was almost fully up at rear when left at highest last night. Front has never been a problem on this car.
Could be caused by the fact its on hydracleanse right now.

BTW - freshly MOT'ed this morning at 10 o'clock. 2 remarks : driver's (LHS) door hinge/pillar faulty (usual corrosion). Numberplate light faulty. But no re-MOT required.

jeremy
Posts: 3959
Joined: 20 Oct 2002, 16:00

Post by jeremy » 25 Jan 2006, 12:44

Strange - as I'd have thought that removing dirt would have increased leakages from elderly components which is why I've never done it. perhaps in fact the dirt was restricting the proper operation of a valve - doseur or height corrector?