Workaround for bubbles in LHM return flow

[MatPL]

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.

I have these symptoms. In addition, a hissing sound from the steering valve.

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.

- My tires are always inflated a little less.
- I can't bleed the system because the air constantly appears on the pump supply line, which distributes the air everywhere. Rear brakes become airy after a week of driving.
- The oil level is always above the norm. I leave the car and release the pressure. Then pour it to the upper limit of the filter.
- I have dirty oil. I poured 30l ON through the system. Later hydraulincage. The oil is still dirty. I suspect that the air is used up too quickly.

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.

For me the problem is also on the first axis. I drive over the bump with a car slam and jerk. Even small meadows on the road cause the suspension to break out of smooth operation.

[white exec]

The notchy steering confirms excess air in the fluid.
Hissing when the steering is put on full lock (left or right) is normal.
The LHM should not be dirty. Is it clean now? Not sure what you meant by '30l ON'. What was that?
How long was the Hydraurincage in the system for? How long ago did you use it?

A couple of other questions...
- Do you have additional protective diodes fitted to the suspension Electrovalves?
- Have you fitted any suspension mode monitor LEDs, so you can see when suspension is Firm/Soft?
- Have you ever opened up the suspension EV solenoids to check the small springs?

After the car has been driven for a few km, could you dip a sample of LHM from the reservoir with a small clear container, and post a photo of it, to show any bubbles there?

[xantia_v6]

I remember that one person found that the plastic top of the LHM tank had a crack in the port for the suction hose, and that caused an air leak that was very difficult to find.

[MatPL]

Hissing when the steering is put on full lock (left or right) is normal.

I'm not talking about a full block, only a slight turn when driving on a roundabout.

The LHM should not be dirty. Is it clean now? Not sure what you meant by '30l ON'. What was that?
How long was the Hydraurincage in the system for? How long ago did you use it?

Unfortunately, it is not entirely clean. I flushed ON / DIESEL fuel. I gave a clean diesel to the pump. I caught my return to another tank. I picked up and left the car. After that I poured hydraurincage for about 3k km. Later change to LHM + Total. I used Hydraurincage in 2011. how I started fighting the badly working suspension.

A couple of other questions...
- Do you have additional protective diodes fitted to the suspension Electrovalves?
- Have you fitted any suspension mode monitor LEDs, so you can see when suspension is Firm/Soft?
- Have you ever opened up the suspension EV solenoids to check the small springs?

Yes, I have additional diodes installed but at the computer. I also have leds. The computer has not reported any error for 3 years! All sensors are working properly.
The solenoid valves have been dismantled and are sealed in hard and soft mode. I prepared HA blocks from Xantia and tomorrow I will try to mount a new Xantia block with a spring on the rear axle. I'm just not sure which hydraulic hose to disconnect from the system. The one that goes from the SC.MAC valve to the solenoid valve. And this free hole in SC.MAC. blind with a vent? Unfortunately, the Citroen documentation download does not work anymore.

I remember that one person found that the plastic top of the LHM tank had a crack in the port for the suction hose, and that caused an air leak that was very difficult to find.

I had another tank from XM and CX, and the problem was the same.

Today I made a partition in the tank. For now I will watch how it will behave.

[white exec]

You have been really thorough with this, including protection diodes and LEDs. Thanks for all that background info, which is important.

Steering should only hiss extremely quietly in normal use, although more loudly at full lock. Suggests air there.

LEDs: Do these remain on (=Soft) when the suspension crashes, or do they momentarily switch off?

Have asked Marc to look at the link to the Citroen working paper on the HA blocks. He should be able to do this quickly, but if you are stuck, send me a PM with your email address, and I'll email the document to you.

Can you post a photo of a dipped sample of aerated fluid from the reservoir?

[MatPL]

The diodes remain when it is soft. If the sensor catches an error, they continue to glow as it is soft. It does not light up only when starting the HA self test.
I'm going to buy a 24mm long cap to unscrew the solenoid valve and then to the garage to pull some oil from the tank.

[white exec]

That confirms the crash is not caused electrically (suspension stays in Soft mode), but is hydraulic.
Citroen paper on the way to you.

[xantia_v6]

Have asked Marc to look at the link to the Citroen working paper on the HA blocks.

I have amended the link to point to a copy on this server. https://frenchcarforum.co.uk/TechDocs/P ... lution.pdf

[MatPL]

That confirms the crash is not caused electrically (suspension stays in Soft mode), but is hydraulic.
Citroen paper on the way to you.

This is not an electrical problem. I changed to computers. I adapted the old H4 computer to the H5 version and it was the same. I checked the computers impulse and everyone had similar parameters. Old H4 had a more complete impulse. H5 less filled.

Zmieni?em link, aby wskazywa? kopi? na tym serwerze. https://frenchcarforum.co.uk/TechDocs/P ... lution.pdf

Thank you very much!


P. S.
Today, oil looks better! A lot less air blisters. Maybe this partition in the tank helps a bit in not spreading the air around the system.

[MatPL]

I changed the HA blocks. I did the front and back. By the way, , I gave new seals for EV solenoids because I had to disassemble them into parts. After all, the rear suspension works smoothly all the time! Almost like in CX. The front bends less than before, but in the front I had a block with Xantia chokes installed and probably that's why I hit the bottom bumpers sometimes. It is more stable. He still shakes on the holes and makes noise. Now just the front axle. I still need to change the front cylinders, because on the left side it makes a lot of noise and seems to be loose. I will drive and test so that I bleed as soon as possible.

[white exec]

Some real progress, there. You have been extremely busy to get all that done so quickly!

It is important to fit your original XM damping inserts (two for each HA block) into the new Xantia valves.
Xantia has a different damper front and back, and different to XM.
XM dampers are the same front and back.
The damper inserts have a small dotted stamped number stamped on them (next to the small hole in the steel).

You should have four with the the same number - they come from the XM, and are the ones to use.

The centre spheres should also have NO DAMPER INSERT in their necks, just a large (5mm) hole, because the damping is in the block, not the sphere. An incorrect sphere here would result in a very stiff ride.

You really do know how to crack through the work, and have some good XM knowledge there. All good stuff!

The fluid is looking very much better, too.

[MatPL]

There were other chokes in the block in my XMie. All plates full and 1.16-1.18mm hole. I drilled them 1.2mm. As you showed in the picture, I pulled out of the Xnatia block with a 1.1mm hole and I had one previously mounted on the front. So many years of checking these components gave me practice and I unscrew and tighten everything with my fingers
I have, of course, balls without 70bar glands. Corner I have factory 40bar and 0.6mm gland maybe because. Maybe there were other chokes in the blocks in 2.9V6?

[white exec]

Blocks = HA regulator valves
Chokes = dampers
Good fun, isn't it?

OK - XM has 1.25mm holes in both front and rear HA regulators (blocks).
This is a fairly large hole, as they go, so a waftier ride than some other models, probably due to the greater weight (inertia) of the car, which provides some damping of its own.

Xantia has 1.1mm at the rear, and 1.1 or 1.2mm at the front (depending on the model).

All the details are here, page 251?
viewtopic.php?p=590278#p590278
Hit the "2001" under XM S2, to download the Citroen booklet.

Front corners for V6 saloon listed as 450/40/0.7
Rear corners for V6 saloon listed as 400/30/0.6
Front HA 450/70/--
Rear HA 400/50/--

Note
We never could make any sense of the engraved/dotted numbers on the damper inserts. The numbers don't seem to correspond to drilling size. (I measure drilling size with a needle, coloured with felt pen, then pushed into the hole. This marks the colouring, and at this point I use a micrometer on the needle to measure the diameter.)
As well as the drilling, there is also the matter of the washers (or stack of them) used on the outside of the damper. These allow a large flow of fluid to by-pass the small hole, in the case of impact or rebound. We do not know anything about how these washers are selected. Likely a secret factory listing, with both hole and washers specific to individual type dampers.*
For this reason, it is important (we assume) to stick with the dampers originally fitted to the car.
*For non-Citroen (aftermarket) spheres, we can only guess whether the various manufacturers have any accurate specifications for the washer stack. Sure, the spheres will work, but how well in the case of impact and rebound?
Personally, I use genuine Citroen spheres, and fit them with Tecnosir (Valprex) regassing valves. This gives genuine spheres a long life, and can allow their pressures to be properly set, and prevented from dropping so low that the sphere is ruined. I now check sphere pressures roughly every 3 years.

[MatPL]

OK - XM has 1.25mm holes in both front and back HA regulators (blocks).
This is a fairly large hole, as they go, so a waftier ride than some other models, due to the greater weight (inertia) of the car (which provides some damping of its own).

I spread out a few HA Xm blocks and none even had 1.2mm. Your HA block had 1.25mm you measured it?

Front corners for V6 saloon listed as 450/40/0.7
Rear corners for V6 saloon listed as 400/30/0.6
Front HA 450/70/--
Rear HA 400/50/--

He agrees here. I measured the front corners with a drill and it came out about 0.6mm. Rear corners have an IFHS replacement and there is no dedicated ball up to 2.9V6 and I have 0.7mm on the back.

[white exec]

I spread out a few HA Xm blocks and none even had 1.2mm. Your HA block had 1.25mm you measured it?

I've measured a few sphere dampers, but not those that were in the XM when I fitted the new regulators.
I just took them out, and moved them across into the new units.

Book says 1.25, so just slight larger (less damping) than corresponding Xantia ones, which makes sense, as XM is a heavier car.