Workaround for bubbles in LHM return flow

[Mandrake]

Yes, I'd go along with that James...

I don't think my purser would though.

Hydraflush was pretty expensive and hard to get last time I checked ?

[Hell Razor5543]

True. According to GSF it is around £50;

http://www.gsfcarparts.com/catalogsearc ... hydraflush

But you might want to check out e-bay;

http://www.ebay.co.uk/itm/980PC0130-CIT ... SwLVZVxx2n

[Mandrake]

Does anyone remember how many litres a full LHM change takes ?

I don't see anything that says how many litres those bottles contain...

[Hell Razor5543]

I have used Hydraflush in the past, and the bottles have always held 5L. I know that when I used it on my BX, and both of my Xantias (6 spheres only) I had over a litre left each time.

(The e-bay image is large enough to make out 5L lower right).

[Mandrake]

Thanks. With all the other money I'm spending on the car just at the moment (including new tyres) I can't really justify Hydraflush that then needs to be replaced again next year.

I will order another 4 litres of LHM (I already have a litre) and do an LHM change though - probably at the same time as I do the o-ring in the hydraulic pump to minimise wastage.

[white exec]

Hydraurincage is definitely 5L. I last paid €30 here in Spain: was priced the same as LHM, but that may be a local thing. The Citroen main dealer had never heard of it, but did order it for me when I confronted him with a part number.

Simon, I think your recent theory about air ingress being worse at high pump speed is a plausible one.
In your case - where you have been plagued by repeated harsh running - I do have a question, though:
When it's harsh, are bubbles - of any size - visible (by dipping) in the reservoir fluid?

I do not currently have a harsh running or crashy problem, and haven't now for over 18 months, irrespective of how or where the car is driven. What I also do not have is any bubbles (of any size) in the reservoir, even after an long, hard, hot run. I guess this is how it ought to be. Unfortunately, I can't say whether there were any when things ran rough, because I didn't look for them. All I can say is that I never saw foaming in the reservoir.

[RichardW]

I will order another 4 litres of LHM (I already have a litre) and do an LHM change though - probably at the same time as I do the o-ring in the hydraulic pump to minimise wastage.

there's about 5l of LHM in my garage which is no good to me! It's of indeterminate age, but all new, it would certainly do as a 'flush' to put in for a few k miles. I had a litre of hydraflush too until a couple of weeks ago that could have been mixed in....

[Mandrake]

I will order another 4 litres of LHM (I already have a litre) and do an LHM change though - probably at the same time as I do the o-ring in the hydraulic pump to minimise wastage.

there's about 5l of LHM in my garage which is no good to me! It's of indeterminate age, but all new, it would certainly do as a 'flush' to put in for a few k miles. I had a litre of hydraflush too until a couple of weeks ago that could have been mixed in....

I haven't ordered anything yet, and wasn't planning to for a little bit yet...

If you have some that is new unused and in original bottles it should be fine - I don't think LHM would deteriorate on the shelf, certainly not over the few years since you had a Xantia.

If you were binning it anyway hold onto it and I'll grab it from you next time.

[Mandrake]

Simon, I think your recent theory about air ingress being worse at high pump speed is a plausible one.
In your case - where you have been plagued by repeated harsh running - I do have a question, though:
When it's harsh, are bubbles - of any size - visible (by dipping) in the reservoir fluid?

I haven't checked in quite a while but a couple of nights ago I got home from a 20 minute drive where the ride had started OK but got quite harsh by the time I came home. I took a photo just after I arrived home with the engine still running but had difficulty getting my phone to focus on the surface of the oil even with manual focusing, because it couldn't "see" the oil until the flash came on, so it kept focusing on the outside of the tank, but you can still see the bubbles:



Towards the top (the edge of the filter) you can see a few normal sized bubbles but the rest of the oil was absolutely full of loads of what we've now come to call "microbubbles"... bubbles that are about the size of a pinhead and presumably small enough to pass through the filters unhindered.

Some potentially very good news though - today I finally got around to replacing the leaking o-rings in the hydraulic pump - the top o-ring I changed in-situ a couple of months ago but the bottom one had started leaking more and more so I spent most of the afternoon taking the pump out and changing the two suspension/brake output piston seals and also the large seal on the power steering end cup.

I also had to replace the 50mm rubber joiner stub on the pump inlet hose, (unique to the V6 pump) as it was so hard and moulded to the shape of the spigot that it was impossible to remove it without it splitting on me. Luckily I had a piece of suitable hydraulic hose to replace it with. On reassembly I was extra careful with the clamping of the joiner stub to get the best possible seal, for example making sure that the bottom hose clamp was just past the bump on the spigot end rather than too far down.

I deliberately left the tank end of the inlet hose alone so as not to disturb the silicone I had previously added. I did have to remove the "mystery o-ring plug" though - turns out that its extremely useful for introducing a deliberate air lock so that when you disconnect the hose at the pump end it doesn't syphon the entire contents of your tank out all over the pump... I did not re-silicone the mystery o-ring plug, just pushed it back in, for now.

After everything was back together I primed the pump with the bleed screw open, (to my surprise it self primed easily even though the entire length of inlet hose was full of air after reassembly) let it idle for a few minutes until the bubbles on the oil surface calmed down, closed the bleed screw, lifted the car right up and down once then back to normal height and went for a drive.

WOW. The ride was absolutely fabulous. No trace of harshness at all, also it did not seem to deteriorate at all over the period of the test drive, even though I was doing things to provoke it like heavy acceleration (causing lots of rear height corrector action) and using sport mode, causing the engine to be revving fairly high.

The ride was even better than it was when I first applied the silicone at the tank end all those weeks ago, I would go so far as to say that the ride was pretty much perfect - no harshness and riding about as smoothly as I have ever seen on a Xantia. At speed it felt extremely smooth and stable with a nice waft but with no pitching or wallowing.

When I got home again I checked the oil with a torch while the engine was still running - absolutely zero trace of microbubbles, just calm and still oil even though the engine was running.

In case anyone thinks its only riding better because of the inevitable de-pressurisation followed by Citrerobics in the course of doing the work, in the last few weeks I have been de-pressurising the car over night 2-3 times a week because of the temporary improvement in ride it gave, but it would always start to deteriorate again the more I drove the car, especially when driven multiple times in the same day.

Will the ride remain this good ? I don't know, lets see...

If it remains good, what was it ? Was it just the rubber inlet hose leaking on the pump, and possibly leaking worse when the pump got hot with engine heat ? A leak there would tend to leak oil when the engine was stopped, but suck air in when the engine was running.

Or could the leaking bottom o-ring have been a contributor ? I'd need to study the internal diagram of the pump again to work out whether that o-ring is always subject to pressure or whether it's subject to vacuum on a part of the pumping cycle.

[CitroJim]

That's great news Simon, excellent!

Yes, I've had monsterous problems with those stub hoses in the past... Always leaks but only when stationary, never when in motion so by that inference it would have been drawing air...

Fingers crossed it all remains good....

[white exec]

Simon,

Great news, after a very methodical check - nothing less than we'd expect!

You've obviously swatted the air-ingress at the pump, but what is also interesting is that the microbubbles have also disappeared. With any air getting into the system, the filters have the job of reducing it to microbubbles (they can't do any better than this, a function of mesh size).

Looks, then, like
1. the presence of microbubbles is a good indicator that air is getting into the system
2. visible foam/large bubbles is a sign that the air ingress is so severe, the filtration cannot cope.

Additional confirmation of this is that, when the ride is good (eg yours today, and my XM ) there are no bubbles of any kind visible.

[MatPL]

Hello everyone. Have you found the problem of microbubble formation in LHM? I have this problem for about 10 years in XM HA2 2.9V6 2000. I change all hydraulic components, and the problem with air is still there. I have made 10 min mod, unfortunately, there is not much difference ... I recorded a few videos to show the problem. I have already replaced about 5 pumps (each sealed with new simmering), LHM tank with CX, and (without O-ring), a few Conjectors (adjusted to 143-166bar and internal tight - pressure drop within 3min is only 6bar). Where is the problem in the appearance of air? Thanks for the help. Mat.

[white exec]

Hi Mat, and welcome to the forum.

Your first video shows a lot of air in the pipe, but which pipe is this? The one from reservoir to pump?
The second two videos show very little air - again, which pipes were these?

Just for info, one of the important functions of the two nylon mesh filters in the reservoir is to break up air bubbles, and prevent them from being re-circulated into the system. It is important that the filters are not damaged, and are fitted properly.

If there is a lot of air in the fluid in the reservoir (dip a sample with a small clear container to check), it is important to check where this is coming from. There are pipes returning fluid to the reservoir (the big one is from the steering; the smaller hoses from other parts of the system), and you could check each one to see which is bringing air in.

If there is little/no air in the reservoir, the most common cause of air getting in is the suction hose from reservoir to HP pump. This should not be fitted with worm-type (Jubilee) clips, but properly circular ones, so there is no distortion of the hose when tightened. If necessary, cut back and remake the connections.

One member did report that the connection for this hose was leaking at the delivery spout on the reservoir, as it had a very small crack there.

You could also try allowing the pump to suck fluid from a known air-free container of LHM, to confirm whether the pump itself was a problem, although not likely after all your careful replacements.

Finally, what symptoms are you suffering?
Crashy suspension? Notchy steering?

[MatPL]

The first 2 videos are the hose supplying the LHM pump.
3 video is a return from the steering wheel and conjector.

In the first film, as I hit the tank, large bubbles appear going to the pump.

On the second video like enlarged video. When you release the movie you will see a lot of micro bubbles. This emulsion is drawn in by the pump and distributed throughout the entire hydraulic system.

3 film is a big oil return. Inside the mounted filter there are many more micro bubbles but they are not visible on the recording.

I have filters installed and they are clean. I put a sponge in the return filter to dampen / disperse the air and clean the oil.
I have already replaced the supply hose several times with different diameters. I have bands that tighten around the hose.
The air comes from the suction hose pump, pump or later from the conjector. When he releases oil sideways, I can see the air coming back.

The problem is that the suspension does not choose fast bumps. He jumps at them with a bang instead of absorbing them, and at the same time is very soft on the wavy road. The conjector's ticking is very loud and metallic. In the morning after starting the engine, the conjector ticks gently.
At a standstill and while driving, the suspension sways very much, because it is soft but not fast in picking unevenness. Like air-braked brakes, it works late.

[white exec]

You have done all the right things, and been very thorough.

A number of micro-bubbles in the fluid going round the system is acceptable, but large bubbles (0.5mm and bigger) are not.

Your last video (rear end bounce test) looks good, with height being corrected properly, so Soft mode looks to be working ok.

Is the steering at all 'notchy' (where you can feel small ripples/lumps as you turn the wheel) ? This is a pretty good indicator of serious air in the fluid.
___________

"The problem is that the suspension does not choose fast bumps. He jumps at them with a bang instead of absorbing them, and at the same time is very soft on the wavy road."

You've hit on H2's one real fault - not being able to deal with sudden changes in road height (eg a ridge across the road), where there back end of the car, in particular, 'crashes' over the step, instead of absorbing it. This can happen whenever such a ridge is taken at a brisk pace.

Reason for it is that the sudden jolt (suspension movement) can send a hydraulic pulse through the system, which momentarily puts the suspension regulators (centre sphere units) into Firm mode - hydraulically, not electrically - by flipping the small shuttle valve in the regulator. This isolates the centre sphere (which provides Softness) just when you really need it, and you're left riding on the corner/wheel spheres (=Firm ride). This unwanted firmness is much more noticeable at the back end, mainly because there is far less weight there.

So what to do?

- Avoid any tyre over-inflation, even by a a couple of psi / 0.15 bar.
- Make sure the system is really well bled (do at the brake calipers) by the correct procedure; rear brakes and rear suspension are inter-connected.
- Ensure LHM reservoir level is correct (check the level indicator is working, by lifting it out).
- Run the system on Total Hydraurincage for 1500-5000km to thoroughly clean it out and remove sediments.

- If this suspension crashiness is the only symptom your are left with, then consider replacing your suspension regulators with a pair of late-Xantia type units. These get over the hydraulic shock problem, and give a much more consistent ride, less prone to rear end crashes.
The details are here:
viewtopic.php?p=505370#p505370
The whole thread is worth reading from page 1 if you have time.