Xantia sinks after replacing spheres

[CitroJim]

Is it not more likely to be the anti-sink valves or a leak in one of the rams?

I'd go along with this if it was just one end of the car sinking but I feel both yours, rpaco and VertVega, are sinking fully at both ends. Unless you have duff anti-sink valves at both ends and/or leaky cylinders at both ends, this just can't logically happen and the chances of two being faulty would be nigh-on impossible.

The anti-sink works like this: Under normal running, the main system pressure holds the anti-sink valves open. When the engine is switched off and main system pressure falls to a value below that contained in the corner spheres, the pressure in the corner spheres snaps the valves closed so that there can be no further leakage from the suspension cylinders via the height correctors. It follows that a duff main accumulator would cause main system pressure to fall very quickly and therefore the anti-sink valves would therefore close very quickly. The efficiency of the anti-sink valves can be tested very easily. Have a couple of passengers in the back. Stop the engine and ask the passengers to get out quickly. The rear should rise and then, after 30 seconds or so, fall back to normal ride height. This shows the there is still sufficient main system pressure to keep the anti-sink valves open to allow a height correction. Repeat but ask the passengers to stay in the car for say, five minutes before alighting to allow main system pressure to fall off. If the height rises and stays high when they do alight, this shows the anti-sink is working as it should as the valve is closed and the height corrector isolated. Repeat for the front although you need a good heavy passenger for this test.

If that test passes then the only thing that can cause a sink overnight is a tiny leak somewhere between the corner spheres and the anti-sink valve. It only takes a very tiny leak.

The other thing that will cause it is a flat/punctured corner sphere (or spheres) which causes the pressure held by the anti-sink valve to leak away slowly.

Another rare cause is that the main accumulator is so good and the system so leak-free that the main system pressure falls very slowly and does not allow the anti-sink valves to close in a timely manner.

Yet another rare cause is very dirty LHM that has left deposits on the surfaces of the anti-sink valves and causing them not to shut off positively. A good Hydraflush should fix it.

[rpaco]

I did hydraflush it before changing spheres.

Have found rear nearside sphere joint had a small leak. So have taken sphere off, re cleaned surfaces and seal and put back. Have now got leak down to microscopic level approx 2000th of a cc per day ie 0.5mm³ or less, is it ok to leave this or will it get worse?

Car still sinks overnight, but now only slightly about an 20-30mm rear and front the same.

Notice that in old days when putting fuel in car from fairly empty tank, about half way to full it used to sink slowly then sigh and rise up by 100mm. It doesn't do this now.

[Old-Guy]

This may seem totally irrelevant but - did you bleed the brakes thoroughly (especially the rears) when you fitted the new spheres?

My reasoning is that the hydraulic system serves brakes and suspension. If you open the system by replacing spheres, particularly the the rear 'anti-sink' accumulator, air inevitably gets into the system. 'Citarobics' will soon purge this out of the suspension lines, but the brake lines are 'dead-ends' - hence the need to bleed.

[CitroJim]

That's a good and valid point Guy.

There is an issue here in that if the car does not rise when filling up with petrol (akin to the sit in the boot test) then that shows there is a big old leak somewhere, maybe internal.

This is often indicative of a worn accumulator but if it has been changed, then a leak somewhere is the culprit.

[rpaco]

That's a good and valid point Guy.

There is an issue here in that if the car does not rise when filling up with petrol (akin to the sit in the boot test) then that shows there is a big old leak somewhere, maybe internal.

This is often indicative of a worn accumulator but if it has been changed, then a leak somewhere is the culprit.

Re tried sitting on boot edge- no rise!

No the accumulator is unchanged and immovable by man born of woman. The anti sink on the rear was changed plus the four corners.
Any air from the sphere change will surely be purged by the return from the cylinder.
No I did not bleed the brakes, but will do so tomorrow, but dont see how this affects sinking. Any air in the brakes would produce a long pedal which I do not have.

[CitroJim]

You've got to get that accumulator replaced rpaco. As DickieG said, find someone with a Pleiades tool and a large hammer and the job'll be a good 'un.

The tip about taking the whole pressure regulator off and mounting it in a vice is an excellent last resort.

Whereabouts are you? If anywhere near me then problem solved!

[rpaco]

You've got to get that accumulator replaced rpaco. As DickieG said, find someone with a Pleiades tool and a large hammer and the job'll be a good 'un.


The tip about taking the whole pressure regulator off and mounting it in a vice is an excellent last resort.

Whereabouts are you? If anywhere near me then problem solved!

I'm in south Lincs, Coningsby where the BoB flight lives together with a lot of Typhoons.

If I take the whole regulator assy off, how easy is that? Presumably I will need a new pipe seal if so what size?(or more than one?)
If I disconnect a pipe at the regulator will it not siphon all the LHM out of the reservoir? I don't think regulator removal is in Haynes.
However if I did take it off then maybe I could fix the drip on the endplate, I read in another thread there is an O ring to be replaced.

Do I have to take the radiator out first (1 or 2 or all three, have aircon and intercooler rads as well as engine)

I Need the car on Monday and Wednesday to transport daughter to Osteopath and physio and the Interlagos GP is on this weekend, I am a slow worker and always find it is more complicated than expected and there is no access so cant really start until Thursday. Have about half a litre of LHM left. But am told to bleed brakes so may use that up.

Doubt Pleiades tool will help since approx 4 foot leverage and club hammer have failed also hammer and chisel and electric hammer, so taking off the assy may be best then I can use blowtorch on bracket. (Is LHM flammable?)
[/i]

[admiral51]

Have you tried to do the Acc sphere up
May seem daft but if the thread is rusted just a few mm of tightening may just break the tension on it to enable you to then undo the sphere.I always give my spheres a little tap (with a gentle adjusting implement ) clockwise before i try and undo them ..never had a sphere fail to come undone yet

Colin

[rpaco]

Have you tried to do the Acc sphere up
May seem daft but if the thread is rusted just a few mm of tightening may just break the tension on it to enable you to then undo the sphere.I always give my spheres a little tap (with a gentle adjusting implement ) clockwise before i try and undo them ..never had a sphere fail to come undone yet

Colin

Oh yes I have. "Every which way but loose"

[CitroJim]

The regulator is not hard to remove. Disconnect the inlet and outlet metal pipes, the rubber return pipe and remove the two 11mm bolts and off it will come with a bit of jiggling. Having a sphere hanging off will not help make it easy though as the whole assembly will be surprisingly heavy. Keep very careful note of how all the pipe clamps are arranged as this is critical to pipe life.

You'll need new seals for the metal pipes, one rubber and one metal or two rubber depending on the regulator type you have.

The leak from the end will not be helping matters but unfortunately it is not an easy job to rectify. You'll need a press to push the end plate down so the C clip can be extracted as there is a massive spring behind. Also, if dismantled, the regulator strictly need recalibrating before being put back into service.

Your very best bet, given that the accumulator is so well stuck, is to go and see Pleiades in Sawtry, Cambs, just off the A1M. Not a million miles from you. They could both sort out the stuck accumulator and overhaul your pressure regulator at the same time.

[admiral51]

Oh yes I have. "Every which way but loose"

Ah a little out of my depth now then

Reckon Plaedies it is then if Martin cant sort it ..............

Colin