Workaround for bubbles in LHM return flow

[MatPL]

I'm more wondering about the 2.5 plate in your picture. I had them on the front axle in the HA block with a smaller opening than in the XM 1.1mm and the car was very very soft. If in XM it should be 1.25 and these 2.5 plates it must be like a water bed.

[white exec]

Have just measured the dampers which were originally in my new-type Xantia valves, and all four (2 front, 2 rear) are 1.1mm. The car they came from wasn't a V6 (which has 1.2mm at the front, for the V6 manual), so that makes sense, and matches the data in the booklet.

In Soft mode, our 2.5 is extremely comfortable, especially at speed, but certainly not "water bed". I have laid hands on an XM with "Comfort" spheres fitted, and you only needed to push down on the front end (stationary, engine running) with a couple of fingers to bob it down. Folks who drove it found it quite boat-like. Peter.N. here apparently once tried Accumulator (undamped) spheres on the corners of an XM, and reported being it guaranteed to produce travel sickness.

All I can say is that the 1.25mm HA dampers are standard across all versions of the XM, and we don't get reports of poor performance of Soft mode (where the centre dampers are used). This is also the case for owners who have fitted the revised-type blocks, and who will almost certainly have retained the original dampers.

Mike (xantia_v6) also fitted the revised-type blocks to his XM V6, not long after I did our 2.5.
______________

Worth remembering that "softness" of ride is also affected by
- sphere volume (larger spheres = more pliant ride)
- gas pressure (the higher the pressure, the softer the ride - more gas = a bigger 'spring')
- the damper washers (affect how the car reacts to sudden or severe bumps and rebounds)
as well as the damper orifice.

[white exec]

Discovered a new way of measuring the diameter of the damper drillings... Couldn't find an appropriate mini drill bit, and all my needles were too small, so - reached for a pointed hard-wood cocktail stick (toothpick).

Pushed firmly and squarely into the damper hole and rotated, it forms a step, the diameter of which can be easily read on micrometer or digital caliper. The wood is hard enough not to be elastic, and it gave an accurate reading, which I later checked on a needle, when I eventually found it!

[MatPL]

All I can say is that the 1.25mm HA dampers are standard across all versions of the XM, and we don't get reports of poor performance of Soft mode (where the centre dampers are used). This is also the case for owners who have fitted the revised-type blocks, and who will almost certainly have retained the original dampers.

Mike (xantia_v6) also fitted the revised-type blocks to his XM V6, not long after I did our 2.5.

I wonder if Xantia V6 also had in its block XM dampers of 2.5 plates and a dimension of 1.25mm.

Discovered a new way of measuring the diameter of the damper drillings... Couldn't find an appropriate mini drill bit, and all my needles were too small, so - reached for a pointed hard-wood cocktail stick (toothpick).

Pushed firmly and squarely into the damper hole and rotated, it forms a step, the diameter of which can be easily read on micrometer or digital caliper. The wood is hard enough not to be elastic, and it gave an accurate reading, which I later checked on a needle, when I eventually found it!

A great idea for a quick measurement!

[MatPL]

I found all the chokes from the HA block that I have. 5 pcs XM and 3 pcs Xantia. I measured accurately and XM has 1.15mm chokes in the block with the designation D4. It has 3 plates and I had some older HA block bought with 2.5 plates but also D4.
Xantia 3 HA blocks. They all have 1.1mm and 2.5 plates. Mark 26.
Maybe there is a mistake in the book and it was supposed to be 1.15 instead of 1.25mm? The rear HA block that I used was originally from the factory as it came out and there were 3 plates with a hole of 1.15mm.

[white exec]

Don't think a misprint. This is the full workshop manual page:

[MatPL]

I don't know why this doesn't match with the documentation. I still have a question.
In the front, when you connected the new HA block, you had to put the SC.MAC cable under the side entrance as it was in the diagram? For me, the HA block was already attached to this side entrance and I didn't move anything there. That's good?

[white exec]

From memory, the 3 ports clustered together at one end of the valve are all internally connected together, so it doesn't matter which one you connect to. Apparently, connections to these can vary from Xantia model to model, depending on ease of manufacture. Can't remember now which port I actually used on the XM here.

On the orifice measurement, I do find that measuring accurately to 0.1mm or less can need several measurements, especially with a digital vernier. Micrometer is more consistent. Some tiny drill bits not perfectly round, either.

The dotted numbers are sometimes difficult to read; D4 is probably 04, and 5 and 6 can be a struggle.

[MatPL]

From memory, the 3 ports clustered together at one end of the valve are all internally connected together, so it doesn't matter which one you connect to. Apparently, connections to these can vary from Xantia model to model, depending on ease of manufacture. Can't remember now which port I actually used on the XM here.

On the orifice measurement, I do find that measuring accurately to 0.1mm or less can need several measurements, especially with a digital vernier. Micrometer is more consistent. Some tiny drill bits not perfectly round, either.

The dotted numbers are sometimes difficult to read; D4 is probably 04, and 5 and 6 can be a struggle.

Yes they are connected, that's why I left the cable as it was, but I preferred to ask
I had several drill bits of the same size and their size is confirmed by an exact caliper up to 0.02mm. Unfortunately, I do not have a micrometer, but I think that the caliper should determine this enough with these differences.
D4 is probably 04 as you write

[MatPL]

Suspension still has trouble picking holes on the road and is nervous / unstable to drive. Due to the fact that they are bleed in HA Blocks, I tried to bleed the suspension today. I drained the foam only from the front HA block! I poured 0.8 L LHM from the rear suspension and the pipe is full of air, which did not try to move like larger air bubbles. I have no ideas where the problem is. Soon I will have a new Citroen pump. I will try to match the V6 engine and start testing again.

[MatPL]

Suspension still has trouble picking holes on the road and is nervous / unstable to drive. Due to the fact that they are bleed in HA Blocks, I tried to bleed the suspension today. I drained the foam only from the front HA block! I poured 0.8 L LHM from the rear suspension and the pipe is full of air, which did not try to move like larger air bubbles. I have no ideas where the problem is. Soon I will have a new Citroen pump. I will try to match the V6 engine and start testing again.

[white exec]

Not sure where the air is getting into your system, but if fluid in the reservoir is more-or-less air free, and aerated fluid is not being passed to the pump, and the pump is ok, then you should be ok. On the reservoir side of the pump there is suction, so any ingress of air will not show up as a fluid leak (only air getting sucked in). On the output side of the pump, the pressure is really high (<175 bar), so any leak would be really obvious.

Not sure why you are bleeding at the F & R HA blocks. It is not the correct place to bleed the system. (The bleed screws in the new HA blocks are there just to blank off, not to bleed.)

Correct bleeding procedure for an XM is as follows:

Note:
- No need to bleed at the ABS unit, as the late type Teves ABS unit (which you have) is self-bleeding.
You do need to have the brake pedal lightly depressed - use a weight, or a length of wood between seat front and the pedal. Doing this makes bleeding a one-person job.
- Throw in an extra 1-litre of LHM into the reservoir before starting the procedure.
- The RR caliper bleed screw will bleed most of the system on the car; expect to draw off up to 1.5 litres of fluid here, before it runs clear. Much less at the other three.
- Check the fluid level (gold metallic disc should be between the two red lines) with the suspension on Highest, and engine running, after it's all done.
- Do not re-use any bled-off fluid; always use fresh.

[MatPL]

I did not mean bleeding the system, but checking what the oil inside the system looks like, because driving is far from ideal. Bleed the brakes after replacing the blocks in the same way you gave. I already had 5 pumps and each was sealed. I checked the expenditure of each of them and meets the conditions of Citroen at a minimum level. Approximately 1.1ml suspension and 3.5ml support per revolution.

[white exec]

OK.
All parts of the suspension system are under positive pressure, so any leak anywhere would show as just that - a leak of fluid.
The ONLY exception to this is the suction pipework between reservoir and pump, and the input side of the pump itself, and the "pick up" plastic tubing down into the reservoir fluid. It is these items that are usually the cause of aerated fluid.
I thought from your earlier photos that the reservoir fluid was just about air-free now, so that points again to suction pipework or pump.

One other cause of aerated fluid is a gradual leak of nitrogen gas from one of the spheres into the system, but this is normally all over and complete when the sphere finally empties itself, and doesn't continue for days/weeks.

Not sure whether you've checked the pump by taking its output through some clear pipe (and back into the reservoir) to see whether it is pumping out air. If there is air being pumped out, make a new good tight tube connection from a container of non-aerated fluid, so the pump is just sucking up from a container and circulating it back there.

[MatPL]

The ONLY exception to this is the suction pipework between reservoir and pump, and the input side of the pump itself, and the "pick up" plastic tubing down into the reservoir fluid. It is these items that are usually the cause of aerated fluid.
I thought from your earlier photos that the reservoir fluid was just about air-free now, so that points again to suction pipework or pump.

The entrance to the pump was sealed with liquid metal to be sure. The suction pipe was replaced yesterday again with new matched clamps. I replaced the upper forging in the tank with different ones and additionally with CX connections, this plastic in the tank should not be a problem, because it was the same on everyone. Unless 3 tanks that have the same problem. I had a hose directly in the tank and the ride did not change at all.

One other cause of aerated fluid is a gradual leak of nitrogen gas from one of the spheres into the system, but this is normally all over and complete when the sphere finally empties itself, and doesn't continue for days/weeks.

The air leak from the sphere rather falls off, because it has been going on for several good years

Not sure whether you've checked the pump by taking its output through some clear pipe (and back into the reservoir) to see whether it is pumping out air. If there is air being pumped out, make a new good tight tube connection from a container of non-aerated fluid, so the pump is just sucking up from a container and circulating it back there.

I will try to think about switching the main pressure to some tank before it reaches the conjector. From what I've seen in the transparent return hose, the air only appears as the conjector begins to pump into the tank. When it pumps for suspension, no air can be seen in the pipe.
For now, I ordered new connections from the tank from Xantia. Maybe they will fit into the Xm tank. That would exclude this oil extraction tube and hose connection. I will have a new pump soon. Then the cable itself or some unknown problem in the installation will remain ...