Citroen C5 Mk II Suspension Will not rise

[white exec]

Is the tank is not vented to atmosphere? Would have to be to allow varying fluid level...
If your proposed air pressure is 25psi above the fluid, then the fluid itself will be exerting 25psi on the tank walls: basic physics.

Still unsure about my questions above.

[myglaren]

No, it isn't vented.

[white exec]

Air-tight, or just no vent? How does it cope with suspension being changed from lowest to highest?

[lexi]

Air-tight, or just no vent? How does it cope with suspension being changed from lowest to highest?

It's a weird thing. Although they are pressurised, they are supposed to be vented
This is why if you put excess pressure on the tank with fluid, it either comes out of rear rams or the return pipe connections. If the car is jacked up on low, those symptoms can arise. Always jack car while on high. If car is raised on support ramp with wheels dangling, the LDS cap must be removed, or tank can split.
There have been mods to latest models with micro breathers on caps. The tank splitting is quite common.

[white exec]

What a pig's ear. Why on earth get this so wrong? It's not as though fluid reservoirs were something new...
I'd be tempted to drill a small hole in an early cap. Glad the XM isn't plagued with that.

[howardaskew]

white exec,

I would be careful about drilling the cap. I think the system needs some pressure. If you overfill when UP and then bring DOWN something has to accomodate the fluid. I doubt the system will go pop when all is in order.
If the cap had a pressure relief valve built in with a clear pipe to a clear overflow reservoir (with a warning float fitted) then that would be the ideal.

I have decided to heed the warnings and use a very small child's bicycle tyre as the pressure source.

I am looking to open a bleed valve to see if anything passes when the pump is running.

Gently does it.

Howard

[myglaren]

There is always a hiss when removing the cap.
I haven't had the need to pressurise mine as I have only added LDS once - ages ago and previous C5. This one is slightly overfilled but has not been a problem.
Filled on max height then lowered with the cap on tight it will pressurise a bit.
I think the pre-pressurisation is to help purge the pump after it has been drained.

[white exec]

It's a weird thing. Although they are pressurised, they are supposed to be vented
This is why if you put excess pressure on the tank with fluid, it either comes out of rear rams or the return pipe connections. If the car is jacked up on low, those symptoms can arise. Always jack car while on high. If car is raised on support ramp with wheels dangling, the LDS cap must be removed, or tank can split.
There have been mods to latest models with micro breathers on caps. The tank splitting is quite common.

As you can see, I don't run a C5, so am looking at this purely from a technical point of view.
If what Lexi says above is accurate, someone didn't think the design of this through properly, which is very hard to believe, given the history of the system.
I take it there is no level indicator (window or float).
What are the handbook instructions for topping up or replenishing?
What does Citroen technical literature say about the "new" reservoir design (for whichever MY it first appeared)?
Tank splitting cannot be accepted as commonplace, surely - but it starts to look obvious why this occurs.

[white exec]

Puzzled by the tank venting/not venting issue, found this previous thread:
http://www.frenchcarforum.co.uk/forum/v ... =3&t=28183.

Wonder whether the rather crudely pressurised C5 reservoir might be compensating for the pump's inability to prime, a problem not seen on earlier Citroens.

Also reports about LDS systems having been accidentally topped with LHM, leading to pump/suspension non-operation:
http://www.frenchcarforum.co.uk/forum/v ... 3&start=15
and similar reports on CCC.

The problems (and lack of complete understanding) carry over to C6:
http://c6owners.org/plugins/forum/forum ... p?11657.20

[myglaren]

Kinda difficult to have a vented, pressurised system.
As said, I haven't had any problems with it (but probably will now )

[howardaskew]

Latest update.

Good news. Thanks to Lexia.

I noticed looking at the Suspension/standard parameters/height correction page that the original height of the rear was 17 points

Trying to get the pump to run after a good while I noticed that my daughters bicycle tyre was flat . Looking at the rear height was 36 points.

So that told me that the system could rise.

Using a lot of patience with my Diag Lexia 7.76, I raised the rear by using the raise rear command. Two or 3 times and then checking the height correction.

I managed to raise the rear to 150 points.

I then lowered to 115 points which is the correct setting for driving. It struggled to rise without the Lexia.

I can see the settings change from 115 to 153 and then 175 points as I try to raise the car. The Lexia will not raise the car above the set point.

I had removed the pressure from the Eazibleed (The Haynes manual pictures an Eazibleed for this task) and had fitted the cap back at atmospheric pressure.

I noticed that I could no longer see any fluid in the Reservoir filler well so I refilled with another litre of LDS making 4.5 litres in total. Makes me sceptical of the 4.7 litres and 5.4 litres in total mentioned in the Haynes manual.

Note: I have not bled the system from any bleed screws.

The pump does not sound like my Mk1 C5 it sounds rougher and slower if that makes sense. I will look to replace the pump when I can source the correct unit from Ebay or a vehicle dismantlers.

I thank those who contributed to this thread.

In Summary I found the following useful.

1) Open ring spanner 11mm (Premier Brand) See photos, opens joints without fear of damaging nut head.

2) Lexia 3 (obtained from Ebay for around £108)

3) Eazibleed unit for pressurising system.

4) Measuring tape.

Many thanks

Howard

[white exec]

Howard,

That's encouraging news - well done - persistence pays off.

Not sure about C5, but XM always rises at the back first, with front following on afterwards - probably just all that engine weight.

It is easy to get the fluid level in the reservoir not high enough: presumably there is a recommended filling procedure for C5 (for XM it is to do it with suspension on highest setting, and read the level indicator . . . not helpful in your case, I know . . . which might be a bit difficult for you, if you can't fully elevate the car) and it will be important to follow this. Low fluid level will create all sorts of problems, including aeration and pump and suspension impairment.

It presumably will do no harm to temporarily overfill the reservoir, by a litre or two, provided this is returned to something like normal after the problems are solved.

Sorry if your post has become somewhat hijacked by a (revived) discussion about the LDS reservoir, and its cap. It's obvious that the design workings of this are still not fully understood. Live and learn

Chris

[Gibbo2286]

Kinda difficult to have a vented, pressurised system.
As said, I haven't had any problems with it (but probably will now )

It's not difficult, the supply tank is just that and works like the gas tank, it doesn't need to be pressurised it gravity feeds to the high pressure pump and I'm sure it must be vented to allow for the low pressure ups and downs of the fluid level in the normal course of use.

The need to pressurise the tank after the system has been drained is simply to quickly prime the high pressure pump.

[Stickyfinger]

According to the Citroen tech at Avalon (my local dealer) the tank is not vented.
This is why you get a "hisss" when you undo the cap and also why you should undo the cap when you jack up the car (when in high setting) as that can cause it to split.

[white exec]

It has been suggested that the valved (previously closed) tank cap is simply an anti-spill measure, in case the vehicle rolled.
Maybe.
Still puzzled, as Gibbo suggests above, how the system was supposed to operate satisfactorily with a sealed cap, and no apparent venting.