Anti-sink?

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Chrispy
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Anti-sink?

Post by Chrispy »

Just been reading through a few threads about anti sink and it appears my car should have it. Every time I start it up, the front end rises, then settles down, closely followed by the rear. Apparently it shouldn't do this? It drives fine once it's pumped itself up, it's just waiting that annoying few seconds whilst it does it.
I can't see any leaks anywhere (like drips on the driveway) so any ideas why it's sinking? Is there another sphere that needs doing somewhere? Are these easy to change?
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Kowalski
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Post by Kowalski »

They all sink, anti sink just means it takes a lot longer to sink.
Overnight there shouldn't be any drastic sinking, a little bit is fine but if its down to the bump stops you've got a problem. If the car doesn't sink, then when you start the engine it sinks, that can be a sign that the accumulator sphere needs replacing.
If its slow sinking overnight, there can be lots of causes. If the back sinks, most likely its the brake valve (doseur) leaking. Both ends can also sink if the height corrector, anti sink valve or hydraulic struts are leaking. A lot of ills (such as sinking) can be cured with hydraflushing.
Chrispy
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Post by Chrispy »

Hmm... Well mine you can actually watch the back sink after yo've gotten out and turned the engine off. Takes about 10 seconds after you turn the engine off then it suddenly drops by about 3 inches. It's not slammed to the floor, just 3 inches lower. The front doesn't do it I don't think, just the rear, although every time I start the car after about an hour or so, the front does pump itself up and settle. It's the rear though that sinks real fast after the engine's turned off.
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Post by xantiav6 »

When you get out of the car the suspension rises due to less wight to support (nothing personal), and sinking is just the suspension adjusting back to normal height. Try turning the engine off and stay in the car and you should not notice any sinking.
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Post by Chrispy »

Erm, no, you dont get what I mean. I turn the engine off, then get out, then a few seconds later (5, 6 seconds) the back end suddenly drops about 3-4 inches. If I leave the car for 8 hours and come back to it, it's like there's no air at all in the rear suspension as you set off, and the back is rock hard like BANG going over bumps, until it pumps itself up. Is this the anti sink sphere? It's not leaking fluid anywhere as far as I can see, and it's not a slow sink, but a fast one within the 1st 10 seconds of stopping the engine.
Chrispy
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Post by Chrispy »

Could this be my accumulator sphere? Anti sink sphere? Anyone? Been searching through the archives and there's no definitive answer to this.....
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AndersDK
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Post by AndersDK »

If your Xantia's got the a/s it would have an extra a/s acc sphere under the rear only (no extra on front).
This is recognised by the single small dia (3.5mm) pipe connected at the rear of the sphere.
You need to remove the pipe from sphere before attempting to remove the sphere itself.
I am in fact more inclined towards a linkage problem on the rear HC.
Anyways - have the car over a pit and get a floodlight on the situation.
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Post by RichardW »

Chrispy,
Mine does this too.... Not worked out why yet, but I suspect the rear height corrector linkage is partially seized, and the rear 'overshoots' when correcting itself after switch off. I've got some time planned on car maintenance in June, so hopefully I can sort it then.
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Post by Chrispy »

Yeah, I do have the anti sink sphere at the rear in the middle, attached to a block with a load of valves and pipes on it. It's wierd getting out after turning the engine off and the suspension dropping rather fast down a fair bit. The wheels aren't fully in the arches like when it's fully low, but the tops of the tyres are in line with the wheelarch. Then, when re-starting the car, the front end pumps up in like 2 steps, then back down a touch, then after about 8-9 seconds the rear does the same. If I drive off straight away, the rear has no damping whatsoever, it just crashes over bumps. Then, it pumps up and all is well.
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Post by AndersDK »

<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by Chrispy</i>

Yeah, I do have the anti sink sphere at the rear in the middle, attached to a block with a load of valves and pipes on it.<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">
The a/s sphere has a single small dia pipe attached ONLY.
If you got loads of pipes and an electrovalve you're looking at the Hydractive sphere - a completely different thingy.
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Post by Chrispy »

Right, just been having a play. Done some citerobics and when all the way up the stop light comes on. I'm assuming that means I need a LHM top up. Also, the clicking is every 6 seconds or so when at normal height. Does this mean my accumulator sphere is duff? Any diagnostic tips anyone? It's not hydractive or anything, just the normal 6 sphere jobby...
martyhopkirk

Post by martyhopkirk »

Ahh, mine does this.
Replacing spheres, citaerobics and fettling with anti sink control have shown no joy.
As the wife drives it most of the time I can live with it. It means that the Xant takes 10 - 20 seconds from start up to be ready to roll, wheras the BX takes decidedly less. Im not sure if the 1.9TD has only one valve on the pump for the HP suspension, wheras older cars have two - or I may be talking codswallop and getting confudled with the HDi (which is what I have).
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Post by Kowalski »

If its an HDI it'll have a dual output pump. That became standard after anti sink was introduced.
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Post by Chrispy »

So, what is the cause? How do we diagnose it? How often should the clicking be? Do we do it on full height or bottom?
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Post by Richard Gallagher »

Later models with anti sink have twin outlet pumps which pump LHM at a lower rate, therefore it takes longer for later cars to rise.
The fact that the pressure regulator is clicking in every 6 seconds would point to a flat accumulator sphere or an internal leak.
Personally I would think the fact that the car sinks so quickly when turned off points to a significant internal leak which allows a lot of LHM to return to the tank before the anti sink can switch in and stop the flow.
The other thing that points me in that direction is that after starting, the car starts to lift then drops, possibly due to the anti sink valve not opening before the required pressure is built up on one side of the valve which upon opening meets a much lower pressurised side to the system causing the drop.
Check the return flow of LHM at the tank end by pulling off the hoses with the engine running, the flow should be little more than a series of drips.
As a new sphere is only £20 from GSF it would be a good point to start on a repair if the leak test is does not prove conclusive.
When the car is raised/lowered by way of the height lever does it move smoothly or in a series of jerks?
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