C5 LDS topping

cachaciero · Unread post by **cachaciero** » 24 Sep 2009, 23:39

mark_l wrote:Thanks, Steve!
The only point, that "makes me worry", is pressure in the LDS tank. When I opened it first time (after long period of the system running), the pressure was much more, then next 2-3 times next two days. I suspect, that the pressure will rise and may cause to enother leak.
Do You know where from air comes into the system?

I'm pretty sure that it comes in through the filler cap I believe that there is a non return valve in the cap which allows air in but not out and I suspect some kind of pressure release / safety valve to prevent the pressure rising above a certain value.

(My theory by observation I have not found documentation to substantiate this )

The requirement to pressurise the tank is really only required when the tank and the lines have been drained and is required to prime the delivery line to the pumps, I assume that if this is not done the pumps will not self prime.
I suspect that this is also why the tank runs pressurised to ensure that the pumps remain primed under all dynamic fluid levels. The maximum normal pressure in the tank appears to be obtained by removing the cap, put the suspension on high, fit the cap, and then put the suspension on low, this will suck air into the tank which will then be slightly pressurised at normal operating heights.

cachaciero

mark_l · Unread post by **mark_l** » 27 Sep 2009, 17:42

cachaciero, do you mean "filler cap"-the cap of oil reservoir?
On the drawing above it seems any device like non-return valve is included in the cap, but in Haynes book (Russian translation) nothing is shown.
In the same book they speak about 0.5 Bar pressurizing by using Citroen special tool. I did not find there exact procedure, confirming yours,-interesting, whether volume's difference between upper and lower LDS level may "build" 0.5 Bar pressure.
Anyway-in my case i was not need to prime the pumps-there was enough LDS in the reservoir.

citronel · Unread post by **citronel** » 27 Sep 2009, 20:26

LDS it is hygroscopic fluid so it is not a good idea to allow air contact with LDS.
LDS reservoir cap do not allow pressure escape or air entering inside 100%.

I can tell this from my experience when after I changed my LDS I put a little to much by mistake and at depressurization command from Lexia, LDS fluid started to escape at return pipe - rubber -, at fixing after reservoir was full and cap closed.

mark_l · Unread post by **mark_l** » 27 Sep 2009, 21:26

citronel wrote:LDS it is hygroscopic fluid so it is not a good idea to allow air contact with LDS..

It is new for me. May be it explains "extravagant" bottom of the tank, that may be simply trap for water?
Do they use nitrogen or dry air when replace or toping LDS?
From the other hand it is hard to believe, that LDS don't contact air 5 years or 200 KKm...

Does overflow include non-return valve?

cachaciero · Unread post by **cachaciero** » 27 Sep 2009, 23:17

mark_l wrote:
citronel wrote:LDS it is hygroscopic fluid so it is not a good idea to allow air contact with LDS..
It is new for me. May be it explains "extravagant" bottom of the tank, that may be simply trap for water?
Do they use nitrogen or dry air when replace or toping LDS?
From the other hand it is hard to believe, that LDS don't contact air 5 years or 200 KKm...
Does overflow include non-return valve?

Nitrogen? the manual makes no mention of using either nitrogen or dry air, the tool appears to be similar to a rad pressure tester. LDS is hygroscopic although how hygroscopic is not clear, there is an advisory on the bottle that the oil in a part used bottle should not be used after a few days (can't remember how many exactly but it wasn't a lot!)

There is no overflow, CITRONEL was talking about the fluid leaking from the rubber return pipe when he overpressurised his system.
As regards his assertion that air cannot get out or in; as I remember the cap appears to be more than a simple cap, must have another look tomorrow if I remember / can find time. However there is no doubt that the system does get pressurised after a little use and it sure as hell does not come from any of the spheres so if it doesn;t come by air drawn into the resevoir then I don't have a clue from where it is coming from.

Cachaciero

mark_l · Unread post by **mark_l** » 28 Sep 2009, 07:37

cachaciero wrote:However there is no doubt that the system does get pressurised after a little use and it sure as hell does not come from any of the spheres so if it doesn;t come by air drawn into the resevoir then I don't have a clue from where it is coming from.
Cachaciero

Maybe it comes as result of regular susrension's functioning?
When suspension rise up-LDS level-down, air-in. If air in tank is trapped after suspension goes down back -you receive pressure.
If air non-return & pressure release valves will be "disovered" in the system-it explains everything. 8)

cachaciero · Unread post by **cachaciero** » 28 Sep 2009, 12:37

Today I checked the filler cap for the LDS reservoir and as I remembered there IS a breathing arrangement in the cap, which can be seen as a small hole on the top of the cap and what appears to be some kind of valve internally. Unfortunately I couldn't check which way the air flows (while I could get my mouth around the cap the irregular molding would not allow a good seal:- ).
I am pretty sure that it is out to in, i.e lets air in which would tie up with the reservoir getting pressurised, I also believe that once the pressure exceeds ambient then the valve shuts off further admission of air, this would limit the absolute pressure in the reservoir to the difference between oil volume in the reservoir when system depressurised i.e max oil volume in the reservoir and max oil volume on suspension high i.e minimum oil volume in reservoir.
Any drop in air pressure in the reservoir caused by going between the extremes will be made good by air entering via the cap this would equate to a positive pressure at normal ride height.
I am pretty sure that the valve is only one way as this would explain CITRONELS experience with oil being forced out of the rubber return line when he overfilled the system, had the cap valve allowed air out it would also have allowed the oil out.
This all makes perfect sense to me with one exception, it is important that the resevoir be maintained at ambient pressure as a minimum to ensure that the pump has oil at its inlet, if their was a vacuum or reduction of pressure then there would be risk that the pump inlet could be starved.
The one thing that doesn't make sense? the hygroscopic qualities of the oil, as has been said it doesn't make sense to allow relatively wet air to sit on top of the oil because it will be absorbed into the oil. Only if it was the case that the oil will release the water content when hot but even that doesn't work because as already postulated there is no way for the water vapour to escape. I have to say that this does seem to be a case of lack of attention to detail on Citroens part, maybe a good reason to go back to LHM as has been suggested by one or two:-)

Cachaciero

Unread post by **myglaren** » 28 Sep 2009, 17:36

I imagine that the amount of 'wet' air would be minimal and as it is retained in a closed system once in there the contamination by water would be inconsequential. A small amount remaining in a 1L bottle would presumably adsorb proportionately more water from the relatively large volume of air in the container.
Fully agree with your pressurisation theory, partly as that was what I had considered to be the mechanism from hearing the pressurisation statement.

cachaciero · Unread post by **cachaciero** » 28 Sep 2009, 20:19

myglaren wrote:I imagine that the amount of 'wet' air would be minimal and as it is retained in a closed system once in there the contamination by water would be inconsequential. A small amount remaining in a 1L bottle would presumably adsorb proportionately more water from the relatively large volume of air in the container.
t.

I guess that would be true but of course every time the cap comes off the process is repeated so presumably the amount of water in the oil is proportional to the number of times the cap comes off

. Interestingly I note that new LDS is quite clear however the oil in my tank is slightly milky not sure if I want to read into that what the logic says I should, how much water is to much water anyway??

Personally I can't see the logic in using any hygroscopic oil in an automotive hydraulic application it's plain stupid to me, if I knew for sure that the seals would be o.k on LHM I would think very seriously about going back to it, it's cheap (relatively) and easily available.

Cachaciero

citronel · Unread post by **citronel** » 28 Sep 2009, 21:01

this is how LDS from my car was after 4 years... black:

and new LDS:

Unread post by **myglaren** » 28 Sep 2009, 21:15

I suspect mine looks more like the stuff in the water bottles than that Orengina you have there. Time for a flush, perhaps?
I had a gander at it yesterday, had the front of the car off to access the lights

& the washer pump that ultimately I just left alone.
It was very difficult to see the level and I could see no Max/Min indicators.
I have pictures.

On a camera.

Somewhere

Have you noticed any improvement in ride quality since changing the LDS?

cachaciero · Unread post by **cachaciero** » 28 Sep 2009, 23:47

myglaren wrote:I suspect mine looks more like the stuff in the water bottles than that Orengina you have there. Time for a flush, perhaps?
I had a gander at it yesterday, had the front of the car off to access the lights & the washer pump that ultimately I just left alone.
It was very difficult to see the level and I could see no Max/Min indicators.
I have pictures.

On a camera.

Somewhere

Have you noticed any improvement in ride quality since changing the LDS?

With system depressurised the oil should be up to the level of the bottom of the filler well if that makes sense take the cap of and you will see what I mean, Mine is up to the bottom of the well on low, makes it easier to check and I doubt the slight extra oil has a negative effect.

Cachaciero

citronel · Unread post by **citronel** » 29 Sep 2009, 08:02

I think the suspension it is more comfy now then before, but maybe this can be also an effect of depressurizations of suspension and air removed; if any was trapped inside.

Th strange part I think it is that this Hydractive 3 & 3+ don't have LDS filter anywhere in tank like previous system LHM... another effect of cost saving or it is so well engineered that don't need one.
I hope H3 will last 20 years... till my children will get this car as inheritance from me.

cachaciero · Unread post by **cachaciero** » 29 Sep 2009, 10:16

citronel wrote:I think the suspension it is more comfy now then before, but maybe this can be also an effect of depressurizations of suspension and air removed; if any was trapped inside.

Th strange part I think it is that this Hydractive 3 & 3+ don't have LDS filter anywhere in tank like previous system LHM... another effect of cost saving or it is so well engineered that don't need one.
I hope H3 will last 20 years... till my children will get this car as inheritance from me.

Re Filters see below, last line but one, not changeable me thinks

2 - Built-in hydroelectronic interface - BHI (integrated hydroelectronic
unit)
The built-in hydroelectronic interface which is a non removable single unit,
comprises the following components:
· an electric motor to drive the hydraulic pump,
· an axial 5 piston hydraulic pump,
· an anti-pulse accumulator and flow regulator,
· 4 electrovalves: 2 per axle, 1 for the inlet (to raise the vehicle) and 1 for
the exhaust (to lower the vehicle),
· an electronic suspension ECU,
· 2 anti-sinking valves,
· 6 filters for the hydraulic fluid: one upstream and one downstream of the
electrovalves,
· a pressure relief valve.

As regards air in the oil I am not convinced that the published way of bleeding this system with the Lexia will get all the air out and neither am I convinced that Citrobics will do it either.

My reasoning is thus: the pressure and return line to the cylinders is a common pipe and quite a long one particularly the rear run. When the system is depressurised there will still be oil in the pipe between the cylinder and the BHI, now if in this oil there is also an air bubble when the system is pressurised this bubble will get pumped back into the cylinder. Now you say well if you now put the system on low the oil will run back into the reservoir and carry the air bubble with it but will it? that can depend on a lot of things and I am not convinced that all the air is expelled so easily, the bubble breaks up some of the air being under pressure enters into suspension, the rest of it ends up in very small bubbles in suspension some of which gets back to the tank some doesn't.
My feeling is that bleeding the system on the bleed screws is probably the only way of ensuring that there is no air in the system after a major breakdown of the hydraulics.
It is also my feeling that normal action of the suspension is unlikely to get all the air out any time quick and that just a couple of cycles of Citrobics may also not get all the air out
It is my belief that it would not require much air in the system to make the suspension feel very harsh.

Caveats this has not been proven by myself yet but it is something that I shall be pursuing in my attempts to get my suspension a lot better than it is.

Cachaciero

citronel · Unread post by **citronel** » 29 Sep 2009, 10:49

thank you cachaciero for reminding me to read from time to time the documentation I have and... sometime I post.

Yes there are filters inside pomp and not in reservoir and have no idea if that filters need cleaning or replacing over time, at LDS replacing it is not mentioned anything about pump maintenance, I think NO.

And back to reservoir cap and air, reading that documentation I seen that pun have direct air intake pipe so from me this confirm that reservoir cap it is hermetic and don't allow air & LDS to enter/escape.