Mk1 Sinker Xantia strange hydraulic fault after repairs.

[aerodynamica]

Hi all, I have an early Xantia VSX sinker, 1993, and over the last year or so I've been improving the hydraulics to try and get it as close to as-new function as possible. The Hydractive works well in that it is very soft front and rear and switches to stiff mode and back readily, This improved after reshimming the pressure regulator and overhauling the Flow Divider Valve. All new spheres in the last year including a custom front center sphere (75bar, 500cc instead of 400cc). The HP pump was however, noisy and I sent it off to be reconditioned. It came back all shiny etc and no longer oozing out LHM but still the noisy bearing sound remained. I spoke to the chap at the reconditioner and he said you cannot always eliminate the noise from the pump pulley shaft due to endfloat. Anyway, recently it has been squeaking loudly after being parked up and I acquired a spare HP pump that had -I believe- a better pulley/ bearing assembly so instead of swapping out the full pump I opted to change the pulley over in situ. This isn't as bad as it sounds because unique to Xantia pumps is that the pulley and the flange its shaft attaches through is secured by 3 bolts that go through the HP pump body. It can be changed out. I swapped ot over and added a smear of gasket sealant to the mating face. Torqued up and bled the pump and ran the engine to then pressurise the system - result! the thing runs very quiet! BUT! there was a lot of air being pumped and returned to the LHM tank and this is not getting any better! It is always bad fram a cold start and is affecting how the PAS feels and will surely soon find its way into the brake circuit.

I'd managed to fully eliminate the well-known old problem of bubbles in the LHM for Xantias and XMs by adding extra extensions for the LHM returns in the LHM filter block to return the LHM below the surface of the tank contents eliminating bubbles (it's mentioned somewhere on here in the recent past) and in addition replaced the HP pump suction pipe attachments too. The system was running neat and with absolutely no LHM bubles ever. They are now back with a vengeance and it is something to do with the job carried out. I left it overnight to see if a leak of LHM from the join between the new pulley flange and the existing HP pump would be seen - but it's bone dry. I triple checked the HP pump suction hose connection at the LHM tank as that was the only other thing disconnected at the time and reconnected with a new clip. I don't think it would be this drawing air.

I also checked the LHM filter block plastic pipe connections for a hairline crack as that was what happened on my old XM SEi Turbo - a nearly invisible crack drawing in air to the suction but I am certain the whole filter block thing in the LHM tank is solid.

So where is it sucking in air from?? It seems to clear after a good 45 minutes of engine running but it's always bad from start up.

I did also change the LHM at the time and removed the LHM tank to empty out. I removed the filter block/ pipe connecton plastic from the LHM tank while leaving all the pipes connected and so the pipes would have been all bent up briefly to allow th block to get out from the LHM tank. Would that be enough to cause a split somewhere in the HP suction pipe? I couldn't see any split.

Enyone experienced this before? it is now taking much longer to pressurise and lift up and the FDV valve is now beginning to make the hissing noise that seems to last for ever. No visible leaks at all...

[Peter.N.]

The large hose from the reservoir to the pump can become porous especially where it joins the pump. Check the end especially if it has an elbow formed at the end as the XM does.

Peter

[wurlycorner]

Wow, that's a serious level of detail you have got down to maintenance-wise with this car, I'm impressed - I will never have the time to get down to stuff like this!!!

Interested to hear about these previously documented problems with air drawn in on Xantia's, that's completely passed me by.

[aerodynamica]

Hi guys thanks for your replies, sorry in the delay I'm away with work. That's pretty interesting about the porous piping - didn't think of that. I've ordered a fairly long length of replacement piping to fit. I'm just wondering why it suddenly started, I suppose disturbing the pipe again might have mullered it.
Thanks for your kind words Iain, ha! I'll admit that 'Old Katy's' engine area is looking quite good and as a low- ish miler, she's not bad but there's a few bad bits on the body work unfortunately. Haha I do probably make to much time for my Citroen hobby..

[Peter.N.]

On the XM it went very hard and brittle at the end, probably heat from the pump conducted from the engine.

Peter

[aerodynamica]

Hi Peter, I opted to replace the pipe fully with a new one. 9.6mm inner diameter and a good thought fit. I also had concern about the lhm tank filter block/ pipe connectors. The pump suction pipe connector has a kind of plug on the top - no idea why - i wondered how air tight it was so tested it with a leak down. It was totally fine. All refitted and primed and ran well with minimal bubbles for a good hour or so. Bleed brakes and seming fine. Next morning (sunday) early start to check all was well and as soon as it started the lhm was bubbling up as bad as ever! O well I tried! So I supposed that the pump has to come back out to been fully inspected on the work bench and change the pulley back over. I first checked the accumulator sphere in case it was failed and dumping bubbles in to the return - totally fine and 60 bar after a year. Rebuilt and primed pump and finally it seems all clear.. day later and still good. What a lot of effort just to get it back to the same standard as I already had it!

[aerodynamica]

I'm still puzzled as to why the thing pumped air in when it was fitted with the other pulley. I suppose thee must have been some invisible mismatch on the mating surfaces of the pulley flange to pump body. Although the 2 pumps are the same part for the same model, they appear to be from 2 different manufacturers with minor detail differences.

[Peter.N.]

Hi Graeme

Sorry the pipe was a wild goose chase but at least you have now eliminated it as a cause of the problem. Never heard of a pump causing that, I would have thought that the bearing would have been under pressure and so any leak would have resulted in fluid appearing, anyway pleased it seems OK now and I hope that gives a permanent cure.

Peter

[aerodynamica]

Hi Peter, not at all! not a wild goose chase because the old pipe when inspected was certainly hardened - especially at the LHM tank connection so it's a good thing it is changed. Quite why Citroen chose to route the pipe the way they did is unknown but it is actually very long.

The system is still bubble free after a full 36h rest after taking it out for a spin this evening to check. I had ordered a new Aux belt to fit as the previous one was tight but with the tensioner adjusted at full. I ordered a new one but they have supplied the wrong length and it's too short and cannot fit at all. Annoyng but thankfuly it's a fairly easy thing to replace.

The pump thing was a true mystery! You're right that no LHM ever did leak out from the pulley shaft or the flange so where was the air coming from?

Anyway, so long as it is now happy then I'm happy. Next is the handbrake cables - the RH cable decided to break when the car was up on ramps but thankfully supported by axle stands... otherwise you'd not be getting these exciting updates! I'd have been made a whole lot narrower

[Mandrake]

Anyway, recently it has been squeaking loudly after being parked up and I acquired a spare HP pump that had -I believe- a better pulley/ bearing assembly so instead of swapping out the full pump I opted to change the pulley over in situ. This isn't as bad as it sounds because unique to Xantia pumps is that the pulley and the flange its shaft attaches through is secured by 3 bolts that go through the HP pump body. It can be changed out. I swapped ot over and added a smear of gasket sealant to the mating face. Torqued up and bled the pump and ran the engine to then pressurise the system - result! the thing runs very quiet! BUT! there was a lot of air being pumped and returned to the LHM tank and this is not getting any better! It is always bad fram a cold start and is affecting how the PAS feels and will surely soon find its way into the brake circuit.

You shouldn't need gasket sealant on the mating face between the triangle bit and the main pump body - there is supposed to be a huge o-ring there in a recess! If it is missing, that would explain it sucking in air...

When I overhauled the pump on my Xantia 2.0i VSX about 10 years ago, (disassembly pictures were on here at one point but are gone now) partly in a quest to eliminate the air bubble issue, I replaced the original seal with a square section sphere seal - which is perfect for the job, as Citroen do not list a replacement part for this seal. (From memory it is originally a round section o-ring)

So are you saying there was no seal fitted in a recess on yours ?

[aerodynamica]

Hi Simon, no the seal you mention was in place and while the triangle flange is off it appeared to still stand proud of the surface so should make a good seal. It might be that the use of sealant did cause the air leak the first time although I did use marginal amount of sealant the second time that seems to be working well. I did attempt to replace the O ring with one from my collection of metric O rings but there wasn't any one that fitted.

I tested the LHM tank filter block here to see if there was any leak at the plastic plug (bottom, right here) that is in the moulding. The vise isn't clamping the plastic btw.
20180120_171959 by Graeme McNulty, on Flickr

From the top, filled the suction part with LHM to see if it leaked out from the plug over several hours, or indeed if it leaked out anywhere.
20180120_171951 by Graeme McNulty, on Flickr

It was completely fine.

[aerodynamica]

Anyway, it's still all very good - no bubbles at all after another day. I took Auld Katy to work today (usually cycle) 5.5 miles there and all good. The steering is actually nice and light and smooth.

All new LHM flushed through as well and the sinker is not currently sinking!

After several hours:
Ignore my colleague's BX, Auld Katy is still unsunk
20180124_101818 by Graeme McNulty, on Flickr
This was after 5hours, usually the front is on the stops after 1hour and the rear not long after!
20180124_101831 by Graeme McNulty, on Flickr

By the end of the day the front had sunk a bit but it is still impressive for a 25 year old system!