antisink valve

stephen burch · Unread post by **stephen burch** » 14 Aug 2004, 19:40

I needed to replace the rear antisink valve on my Xantia activa as it was still sinking after replacing the sphere. I bought one from Andyspares (only one listed) and found out the mounting holes were different. I rung someone to find out if the front and rear are different, apparently they are but they will function OK either end. I fitted the part by drilling another hole for the mounting bolt and fitted all the pipes as per the original setup. The problem is that the back of the car doesn't go up, even after going through the suspension settings. I followed the procedure in the haynes manual and did not touch the steering etc. Can anybody enlighten me on the cause and how to fix this as it was rather uncomfortable driving it back from the workshop. Thanking you in anticipation.
Steve.

TheWorker · Unread post by **TheWorker** » 15 Aug 2004, 04:21

make sure you have the pipes in the right holes in the valve and the white plastic clip that goes on the anti-roll bar or if the bracket is broken and the long rod to see if its off the previous mark.
if thats all ok you could have the wrong valve.

stephen burch · Unread post by **stephen burch** » 15 Aug 2004, 12:02

My reckoning is that an anti-sink valve is essentially a non-return valve and I assume that the valve is placed in line with the main feed pipe, (the one in the end of the housing body rather than any of the four side pipes). If this is the case then the only thing that I can think of that's stopping it working is the pressure needed in the system to bypass the valve spring, therefore are the valves rated at the same pressure? I've just had a thought. If I jack the front of the car so the hydraulics think the back is heavier and possibly weight the back end as well hopefully this may provide enough pressure to overcome the valve spring and get pressure to the system. I might find that I'm thinking cr*p but it's worth a try. I'll keep you posted.
Steve.

stephen burch · Unread post by **stephen burch** » 15 Aug 2004, 20:28

Got the car up on stands and tried bleeding the brakes. Front ones bled no sweat, rear ones didn't want to know, so no rear brakes and no rear suspension. Goes without saying but my wife won't be using the car tomorrow. I could do with getting this fixed, the kids are back at school in 2 weeks.

Robin · Unread post by **Robin** » 15 Aug 2004, 20:34

Stephen, you need pressure in the system to bleed the rear brakes. Lifting the rear does not help. Put the suspension on high or in normal but on ramps to maintain system pressure while you bleed the rears.
Made this mistake myself[:I] Robin

stephen burch · Unread post by **stephen burch** » 15 Aug 2004, 23:54

Thanks Robin. Would that account for the loss of suspension as well?

Robin · Unread post by **Robin** » 16 Aug 2004, 02:09

Stephen, the working of the A/S valve is not fully understood by me. It needs pressure from the pump to open it for normal use as I see it. Having taken the unit out and replaced it with the 'correct' ? one I am not sure here. Will the suspension rise and lower on the internal control? Robin

stephen burch · Unread post by **stephen burch** » 16 Aug 2004, 04:25

If the internal control is put through its paces the front works as normal, the back just sits there sulking.
I tried what you suggested but used axle stands under the rear arms instead of ramps , tried to bleed the system with a tube and a bottle....... nothing. Got my son in the car frantically pumping on the pedal.....still no rear brakes, no rear suspension and a son that walks with a limp. Ahh the joy of Citroen ownership.

AndersDK · Unread post by **AndersDK** » 16 Aug 2004, 08:06

Stephen -
The A/S valve is rather simple in function : in principle it works like a heavy duty one-way valve.
In real world under your Xantia, this valve is a dual valve where both valves closes off, WHEN the pressure feed from the car's source of pressure (regulator + accu) is lesser than the pressure in the suspension.
According to Citroen's SC/MAC (antisink system) documentation the front & rear a/s valves are same type of valves, but connected slightly different to obtain the wanted functions, on hydractive models.
HOWEVER : according to the description on XM ('95->), the a/s valve is different for vehicles without hydractive suspension.
This difference could exactly explain why you had to drill a new hole for fitting, as the pipe connection pattern differs such, that you <font color="red"><i>must</i></font id="red"> turn around the valve to fit the pipes [8)]
- and then you get a lock-up for the rear suspension pressure [:(]
I fear you've got the wrong type of a/s valve fitted [xx(]
To prove it, then try the following :
hold the old valve against the new one to compare - such it would line up with original mounting holes and the piping.
It should then look like the new valve has the single "end" pipe port fitted at the "wrong end" - i.e. if this end fitted pipe was moved to opposite end - the new valve would in fact line up with the original mounting holes.

stephen burch · Unread post by **stephen burch** » 16 Aug 2004, 11:29

Anders.... If I read you right and turm the valve so the mounting holes line up with the originals then I would need a pipe extension for the main feed as the pipe is not long enough to reach as per original layout.
However, if I turn it around 180 degrees on its circumference so the feed pipe is at the same end as it is now but the 4 branch pipe holes are the opposite of what they are now (in other words, they are swapped over) then the valve may work. I can re-work any mounting anomalies fairly easily, I just need to get the pipes in the right holes.

AndersDK · Unread post by **AndersDK** » 16 Aug 2004, 22:18

No - you read me wrong [:(]
The a/s valves for hydractive are sort of reversed in function to the non-hydractive valves.
They can NOT be swapped - it's NOT just the pipe connections that differs [:0]

stephen burch · Unread post by **stephen burch** » 17 Aug 2004, 03:51

Good news at last! I had an extension pipe made up for the feed pipe and got hold of a male to male joiner. I turned the valve around so the feed pipe hole was facing the opposite way and the mounting holes lined up with the mounting plate, re-routed the feed pipe and plumbed the whole lot in, bled the brakes with the axle stands under the rear arms and hey presto! It all works fine and the stop light on the dash goes out a lot quicker than before. I then proceeded to take the car home and just before I got to the house I dropped the car down onto its bump stops. I pulled up very slowly as I knew my wife would be watching. I went in with a resigmed look on my face; "it doesn't even go up at the front now!"
"Oh no, something must be really wrong".
I waited a while, "hang on", I said, I'm going to try something". I went out to the car, opened up the bonnet, pretended as though I was fiddling with something, got in and started her up, put the height control in the middle, got out and said "look! It's working!"
You ought to have seen the look on her face. Then I said "I was having you on".
I've never known her to hit me so many times in one go before.
So calm has now returned to the Burch household and we all like the car again. Such is life.

AndersDK · Unread post by **AndersDK** » 17 Aug 2004, 03:59

Right then [8D][8D]
- was'nt exactly what I meant - but never mind as longs as it works [:p]

stephen burch · Unread post by **stephen burch** » 17 Aug 2004, 11:34

Just had a look out the house window, car is still up. Success.
A big Thanks to everyone for their advice and info.