Citroen XM Forum

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http://c6owners.org/plugins/forum/forum ... hp?11657.0.

Could have been a final straw in the kill-off of hydropneumatic models. Wonder how many claims for LDS tanks came Citroen's way?

More about same issue on C5, on FCF.

Makes you appreciate (a) how little cost-cutting was brought into play for the XM, and (b) just how valuable, and detailed, our understanding is of XM design and service requirements. Utterly invaluable.

It sounds like the sonic welding of the tank halves wasn't performed properly. I don't see why the reservoir is pressurised at all, other than temporarily, if a sphere membrane ruptures.

You need to read the threads to appreciate the detail, and the obvious rethinking that was involved.
A totally different pump arrangement to XM and Xantia, which seemingly wasn't self-priming. A real pig's ear, particularly tanks splitting during jacking and MoT testing.

I read the threads adn it appears that the caps originally didn't have vents in, or that are very small, thus hold pressure. In addition some tanks just split in normal use, indicating faulty manufacture. The tank only needs to be a reservoir, so doesn't need to be pressurised.

Dieselman wrote: The tank only needs to be a reservoir, so doesn't need to be pressurised.

I think there's a lot more to it than that, Will.
So why not a simple vented cap, instead of the not one but two designs of valved caps?
And Citroen's instruction to owners to only have fluid added or renewed by appointed dealers?

I suspect the caps are a leak free solution in the event of a roll-over.

Maybe. Wonder whether spilled LDS is a particular hazard.
A whole box of frogs in its wake, though.
Some very unamused owners out there.
Glad not to be one of them.

There appears to be no vent pipe, unlike previous LHM tanks.

Surely, all it needs is a vented cap with a pipe that loops back under the tank.

This issue is exactly tthe same as 2.5TD coolant header tanks rupturing.

Dieselman wrote:I suspect the caps are a leak free solution in the event of a roll-over.

It was a change in the eviroment laws "EU and UK" about restricting or stopping any leaks invent of an accident or over fill, it effected number of points on any car, like car battery's have now got to be sealed and have that jelly kind of acid and not the liquid acid. All this is comes as an added cost to the owner. these new jelly type battery's don't last no where near as long as an unseal liquid acid battery. Its becoming more and more a throw away instead of repairing

Iirc the system is unvented.

When you replace spheres or pipework or even a top up or flush the system needs a lexia to depressurise properly and then you need to apply a certain amount of pressure to the tank to get it to prime the pump and kick in.

It has advantages as in there are no return pipes on the struts, it all goes in and out via one pipe.

To be honest it was a stupid walk away from having a proper pump to try and make it cheaper long term but they still ended up needing a pas pump and then a vacum circuit for the brakes! They should've stuck to it powering the lot and been done with it.

Also reminds me of the Xantia v6/2.1td coolant tanks that split for fun and are now considers consumable items on fcf