Citroen C5 - Changing LDS fluid

[GiveMeABreak]

That LDS did look a bit black to me, so changing 4 litres will be good for the system. Obviously if one is going to replace the LDS fluid, getting as much of the old stuff out is important and depressurising with Diagbox if you have this is an easier and much quicker way to do it and will get more fluid out.

Once you get your ride heights corrected, that will help with the ride quality - definitely seems to be a little high Vlad. As long as you have bled the system properly - that will also help with getting rid of any air in the system.

Good job.

[fikse]

Old tread, still valid and useful. Thank you GiveMeABreak for the fine instructions.
I just did this on my '06 C5 with success.
I want to add a tip: I suspected that the cap on the hydraulic tank was the same as the cap for the brake fluid tank. So I tested with the "One Man Bleeder tool"

Without any brake fluid of course, I connected this to a wheel (with 0,5 bar pressure) and into the hydraulic tank. It worked as supposed, and the bleeding prosess was done fast.
BTW I have used the same bleeder kit sucessfully to bleed a empty brake circuit via Lexia. A long process to bleed the brakes as I was alone to do the job, but it worked fine.

[HydroFreak]

I am about to change the spheres on the front of my C5 (Hydractive 3+) and I bought a vacuum bleeding kit with the capability of 0.5bar on the gauge.

The confusing thing I keep reading is some people seem to be thinking to add positive pressure to the system for bleeding purposes however 0.5bar means reducing pressure (vacuum tool) with respect to atmospheric pressure (1 bar). Makes sense to me if I can apply vacuum of 0.5bar in the air space of the LDS reservoir under the cap that it would draw any air bubbles from the system following factory steps.

Am I on the right track?

[bobins]

Indeed, 0.5bar is a reduced pressure, not increased pressure, and that's (0.5bar) what the workshop manual states - though for the pedants out there, 1bar is not quite atmospheric pressure
However....... the Facom 920 tool is a simple cooling system pressure testing kit, and the pressure gauge on it sits at '0' when at rest. When at rest it's open to atmosphere, so their scale is incorrect as it's showing a vacuum. My guess is both the workshop manual and the Facom tool graduations are a bit of a FUBAR and what they actually mean is 1.5bar.

Fackin' Facom Fubar

[HydroFreak]

Indeed, 0.5bar is a reduced pressure, not increased pressure, and that's (0.5bar) what the workshop manual states - though for the pedants out there, 1bar is not quite atmospheric pressure
However....... the Facom 920 tool is a simple cooling system pressure testing kit, and the pressure gauge on it sits at '0' when at rest. When at rest it's open to atmosphere, so their scale is incorrect as it's showing a vacuum. My guess is both the workshop manual and the Facom tool graduations are a bit of a FUBAR and what they actually mean is 1.5bar.

I don't know what the Facom tool is like but the Repco tool I have is correctly graduated, when you squeeze the hand trigger it generates vacuum and correctly shows 0.5bar as you 'suck' with the tool. I don't think there's any FUBAR in the workshop procedure. For example, if you push air into the reservoir at 1.5bar then you need to use bleed points elsewhere in the system to release trapped air bubbles. There is no mention of doing that in the instructions. Whereas if you apply exactly what they say, i.e. 0.5bar, to the reservoir then that will draw any air towards the low pressure air gap above the fluid in the reservoir and precludes the need to use any other bleed points in the system.

EDIT: you inspired me to double-check markings on my Repco tool and I guess you could say it's wrong in the sense that it uses negative scale, and the needle starts at zero. But I think that's quite forgivable given it's easier to understand vacuum as negative numbers relative to atmospheric pressure. So 0.5bar on the Repco is represented as -0.5bar, i.e. 0.5bar below 1bar (which is represented as ZERO). Vacuum for dummies I guess because it makes sense to me!

[bobins]

The Facom tool is the one in the photo I posted. It's a simple pressure tool, not a vacuum tool. It's used for pressurising the cooling system to test for leaks and/or bleed the system. I think the workshop manual reference to 0.5bar should be read as 0.5bar over atmospheric pressure as the hydraulic system needs a slight over-pressure to prime it after it's been drained.

[HydroFreak]

The Facom tool is the one in the photo I posted. It's a simple pressure tool, not a vacuum tool. It's used for pressurising the cooling system to test for leaks and/or bleed the system. I think the workshop manual reference to 0.5bar should be read as 0.5bar over atmospheric pressure as the hydraulic system needs a slight over-pressure to prime it after it's been drained.

Fair enough, so on that basis it must be a self-bleeding system. Never seen that before but I'm not exactly an expert on these cars!

[MattBLancs]

There's two versions of pressure= gauge and absolute.

In this application it would be normal to take these as gauge pressures, hence 0.5 bar above atmospheric (hence positive pressure)

[Jay-Bruce]

Bravo Matt - spoken like a true engineer