S2 not lifting or pressurising at the front!?

andmcit · Unread post by **andmcit** » 16 Sep 2009, 17:40

Seen on club-xm:

ds21 wrote:Hi, I`ve a problem with a Xantia2 Activa where the front suspension
won`t lift. After checking the hydraulic pressure Ive found that the system is
not building up enough pressure, as though there is a unit bypassing the
pressure feed. What I was hoping for was the layout for the hydraulic system
so I can work out which order it feeds.

Cheers, Andrew

I did originally suggest the front nylon height corrector bone or even the anti
roll bar link onto the nylon jobby before condemning the height corrector
when there was a passing reference to it on another thread but as there is
now a bit more description of the problem, I thought I'd post here.

When the answers start appearing I'll head Andrew over this way!!

Andrew

MikeT · Unread post by **MikeT** » 16 Sep 2009, 21:08

Initial thought of pressure bypass brings to mind the pressure relief nut being loose but would that stop only the front from working?

andmcit · Unread post by **andmcit** » 16 Sep 2009, 21:16

I had an anti roll bar rod snap off the bracket that then left the nylon
dogbone loose so no pressure was fed into the front suspension through
that height corrector. Would certainly be my first point of investigation.

When the height corrector body is left unmoved and get's stiff in it's
movement the weakest point will either be the nylon joint or if the ARB
rod is corroded that could even snap first. Had fun getting the new ARB
bracket on and adjusted correctly to get the ride height doing what it's
supposed to do!

Andrew

KevMayer · Unread post by **KevMayer** » 18 Sep 2009, 20:26

Does it raise and lower to max and min with the height adjuster? I'm pretty sure this will bypass any fault due to the plastic dog bone.

It may be a faulty electrovalve passing in the soft mode. Get him to pull off the electric plug from the front electrovalve and see if it raises when stuck in hard mode.

Does the rear raise as normal?

The pump feeds the accumulator.
The accumulator feeds the security valve.
The security valve feeds front anti sink valve, rear anti sink valve, front brakes and Activa system (including the Activa electrovalve and Activa roll corrector, but, if either of these were passing it would pull down the rear pressure as well).

The front anti sink feeds the front electrovalve hydraulic supply (*) and the front height corrector.

When the front anti sink opens it connects an outlet pipe from the front height corrector through to the front hydractive block. LHM goes backwards and forwards through this pipe to allow the suspension to go up and down.

So, if the front electovalve is passing in soft mode then it is the feed from the front antisink valve to the electrovalve (*) which will be pulled down and will affect pressure build up in the supply to the front height corrector.

If it were my car the first thing I'd try is to strip down the front hydractive block and check the electrovalve small spring (i.e. stretch it a bit) and the inlet O ring (which may have broken).

andmcit · Unread post by **andmcit** » 18 Sep 2009, 22:31

Cheers Kev, I've relayed your info quoted in full on club-xm.
The poster did leave this before I posted your reply:

ds21 wrote:Hi, thanks for your replies. I have fitted a pump and pressure regulator from
a car known to be good just in case they were a problem, but no difference.
I`ve also tried a front height corrector, which made no difference. I think its
something further into the system with a sort of internal leak. I did wonder if
it could be the anti-sink valve or security valve, the security valve does look
wet but this may be due to fluid from the reservoir. I did wonder about the
hydractive units aswell as I`ve read tech bulletins for similar faults with the
seating of the valve.

I fear the owner of this car will give up and send it for scrap if we have no luck.

Thanks, Andrew

Doesn't sound good for the car's chances...

Andrew

addo · Unread post by **addo** » 19 Sep 2009, 09:59

Depends what you're looking for.

andmcit · Unread post by **andmcit** » 19 Sep 2009, 10:49

If get's to that stage, I'll try and get the guy's contact details for you Adam.

Andrew

andmcit · Unread post by **andmcit** » 27 Sep 2009, 20:55

Tonight after working on one of my Activas I believe I've inadvertently caused an identical mode of failure
and found a solution!

There's a main metal feed pipe onto the steering pinion that then turns into a rubber pipe that had perished
promptly plonking out at least 2 litres of fluid and made the steering sluggish as hell and the front height too
low to be on normal running height when I tried to move the car onto ramps to effect a repair. It was bad
enough I believed the front height corrector had given up or a feed pipe off the steering rack return had come
adrift.

After fannying about all afternoon with abysmal access fixing the split pipe, I found the car would lift merrily
to high at the rear end of the car but wouldn't budge a mm at the front whilst sitting on the ramps. OK, feed
more fluid I though after all I'd managed to lose loads by now but despite all efforts to get any movement with
more new fluid and opening the bleed screw on the regulator = nothing. Not even a sound of air off the bleed
vent screw.

I checked the height corrector linkage and wondered if in fact the nylon dogbone joint had popped and then
whether the whole lot was a bit stiff acting onto the "normal" anti-roll bar. First stroke of blind luck/inspiration;
I got my 3.5 tonne trolley jack and lifted the front car onto approximately visually normal /intermediate with
the engine running. The hydraulic pump seemed to kick into a bit more life audibly and I simultaneously opened
and closed the vent screw again with a rasp audible from it this time. Gently lowering the jack away from the
car I discovered it was finally off the bumpstops and supporting it's own weight on the suspension!! Yay!!

Try jacking the car up whilst running it's engine and opening the bleed/vent screw on the accumulator - you may
in fact not put too much fluid in as I have done this evening too!

I then cycled the height from max to min etc several times and then tried bleeding it but no sound again although
the suspension was found to be in tip top condition again!

Andrew

Unread post by **CitroJim** » 27 Sep 2009, 22:06

andmcit wrote:There's a main metal feed pipe onto the steering pinion that then turns into a rubber pipe that had perished.....
After fannying about all afternoon with abysmal access fixing the split pipe...

That's the same pipe as I replaced on my V6 in the week. You're right, it does take a lot of fannying about

Well done for getting it fixed. Abysmal access describes it very well

Personally, I'd rather do a heater matrix than that pipe

That's interesting on the front HC. It must have been an air-lock somewhere but I'm a bit of a loss to explain how it came about except the lock must have been in the functional return circuit as the perished pipe in question forms part of this circuit. Why it should only affect the front though is odd. Good tip to open the bleed valve with a jack under. Inspired

andmcit · Unread post by **andmcit** » 05 Oct 2009, 20:29

I'm guessing that the bleeding and thorough purging of all the circuitry at
the front is a time consuming process on a Xantia and further complicated
by the additional Activa ARCS components so probably opening the extra
circuit lifting the car and altering the attitude of the height corrector allowed
the trapped air to move through the system where it was finally expelled.

Anyhow, all is now well with said car as it passed the magic MOT this morning
with a few silly (minor) advisories! Yay!!

Andrew