Workaround for bubbles in LHM return flow

[MatPL]

No problem. Send e-mail address.

[ksanturion10]

Found it, thanks

[MatPL]

Found it, thanks

Same document? I will add some interesting photos so that you can compare them with your document.

[ksanturion10]

Hi,
yes exactly the same. Actually, two files I found only with different sizes of the pages. Really good source, just what I was searching for

Will check for bubbles and get back.

Nice that you are posting the pages here

[ksanturion10]

OK, went for a 35 km journey around the city. Couldn't check at start up, because the cap onto the LHM tank was hardened from the cold, but after 30 km I've stopped to see a relative of mine, and after an hour started again with fairly warm engine, the cap was OK for removal, so started looking inside the tank for bubbles. At first glimpse there was nothing, but when I went closer I saw the micro bubbles into the flow coming from the steel mesh filter. The bubbles, I told you I saw before the overhaul of the pump and the intake hose, were clearly visible and significantly bigger. Now even with high RPM at stationary vehicle there are only micro bubbles and a little bit more fast flow through the mesh filter (it needs cleaning though).
It is possible the bubbles coming into the tank to be actually more bigger initially and then get microfied through the mesh filter, but still don't believe they could go into the HP circuits so easily, and if they actually could get there, the count of micro bubbles per cm^3 of LHM is so small, so I do not believe they can influence the compressability of the fluid anywhere around the suspension. Haven't seen any leakage around the pump and the pipes connected to it
With such extensive information at hand, I would check again very carefully around the height correctors and their linkage, as they are really crucial for the propper functioning of the suspension. After all, the Hydractive system is again plain Hydro-Pneumatic system, but with an electronic control

drBR
Martin

[MatPL]

It is possible the bubbles coming into the tank to be actually more bigger initially and then get microfied through the mesh filter, but still don't believe they could go into the HP circuits so easily, and if they actually could get there, the count of micro bubbles per cm^3 of LHM is so small, so I do not believe they can influence the compressability of the fluid anywhere around the suspension

Did you shine a flashlight with a narrow beam of light on the tank? Without light, I cannot see air in the oil, only sometimes large bubbles, which, as you write, should not get into the pump, because they have a large displacement and easily rise up. Small amount of microbubbles per cm3 I will agree, but go back to page 12 there is a video of the pump feed hose. This is idle work, and as I increase the engine RPM the number of microbubbles increases. They cannot be seen without the backlight of the cable. The front height adjuster has a slight leak around the diaphragm sealing ring. I'm already preparing a new one.

[white exec]

I suppose it's possible that microbubbles that get recirculated into the system could amalgamate in slow-moving parts of the system to form larger bubbles (or even air pockets), which could affect ride quality.

Slow-moving parts of the system would include spheres, brake calipers (which are actually 'dead legs'), and maybe height correctors. It's only the steering that works with a high flow rate in normal use.

My preferred method of assessing what sort of bubbles are in the reservoir is to dip a sample of the fluid with a small transparent container.

[MatPL]

My preferred method of assessing what sort of bubbles are in the reservoir is to dip a sample of the fluid with a small transparent container.

I made 2 attempts.
1 photo after driving 10km in the city, I let the engine run at idle for about 10 minutes (then the conjector turns on every 5 minutes or less) and after this time I took a sample from the tank as in the first photo.

2 photo after driving about 3km with different engine revolutions and turning the steering wheel (conjector turns on every 20 seconds).

[ksanturion10]

It is possible the bubbles coming into the tank to be actually more bigger initially and then get microfied through the mesh filter, but still don't believe they could go into the HP circuits so easily, and if they actually could get there, the count of micro bubbles per cm^3 of LHM is so small, so I do not believe they can influence the compressability of the fluid anywhere around the suspension

Did you shine a flashlight with a narrow beam of light on the tank? Without light, I cannot see air in the oil, only sometimes large bubbles, which, as you write, should not get into the pump, because they have a large displacement and easily rise up. Small amount of microbubbles per cm3 I will agree, but go back to page 12 there is a video of the pump feed hose. This is idle work, and as I increase the engine RPM the number of microbubbles increases. They cannot be seen without the backlight of the cable. The front height adjuster has a slight leak around the diaphragm sealing ring. I'm already preparing a new one.

It was dark, so yes, I used a light. From my practical experience, and from some old posts into this forum, large bubbles at the mesh in the tank are pointing to some sort of a fault somewhere into the hydraulic circuits. Hence the leak you found now .
I think it is exaggerated to call them micro bubbles, to me this is something around 10-th to 50-th of the millimeter in diameter ( ), and second, I think we are only seeing a count per cm^2, so what floats onto the surface layer of the LHM in the tank (or onto the walls of your transparent syringes). If true, that amount per cm^2 can not influence anything in the HP cirquits, and I think we are forgetting something really important - the leakage returns at the height correctors, I don't see any reason, why those bubbles couldn't be expelled from there.
So, you see my point, those bubbles are something, that has been taken into account with the development of the system, and for me it is certain that they can not influence it at a such degree, as to harden the suspension or make it less responsive. I don't want to state my tick time at the conjecteur, as it is hilarious, compared to your 5 minutes at idle , and still I get only miniature and very few bubbles into the tank, and even at higher RPM/encreased flow.
Don't get it too complicated, they won't give us the Nobel prize

[MatPL]

Leakage is too much to say. I had already at the end of summer. So I put on 2 height correctors. The ring has 2 slightly different diameters. I have noticed this recently and at the moment the rear is dry. I got the oil from the bottom of the tank near the filters, not from the surface of the oil. If this air in the oil has no influence on the HP suspension and power steering, why after 1 km traveled the suspension starts to make noise and roughly dampen and the power steering works louder (you can hear the oil flow). Conjector greatly shortens switching on sometimes to 13 seconds? But how the suspension works for a long time at idle speed, sometimes it shows more than 7 minutes between switching the conjector. In the morning, when I leave the parking lot right after lifting, the ride is smooth, and the power steering does not make any sounds and works very lightly / smoothly. For about 1km ... I don't want a Nobel Prize but I would like a properly functioning suspension all the time, not 1km

[ksanturion10]

These are old cars, old worn hydraulic pistons, rubber piston rings and etc. Something has to be replaced, that's all.
For example, yesterday before going onto my trip, the car started roughly, because of the cold, and the STOP and hydraulic lamp illuminated constantly until I decided to turn the wheel left to right briefly and the lamps imediately went off. In general they illuminate at start for not more, than 4-5 seconds. So I guess something was stuck, and imediately it gave an effect over the hydraulic pressure. I have the same simptoms like you are describing, but I know now for several months, where is the culprit in my case, and no, it is not the minute quantities of air, which are showing at the tank . Just don't have the right place to rectify the problem, and the weather is not very favorable right now
Maybe something, that will be at help for you. You say "right after lifting" - for several months I stopped lowering the car, when left over night, so no excesive pumping at start any more. After all, those anti-sink valves are there for a reason . And apart from the "real deal" problem I found, the suspension seems to work better now.

[MatPL]

My CX is older like most Xantia and XM and drives very well, why can't 21 year old Xm? Chris doesn't complain about comfort in his XM I don't leave the suspension everyday. In the morning after starting the engine, the rear suspension drops a bit and is leveling out. Something needs to be replaced, but what if everything I could in the car was replaced several times and nothing brought the desired result. Unless I forgot something during the 11 years of driving this Xm? The biggest improvement was filtering all the oil returning from the conjector and the steering gear to the tank on a regular basis through a sponge

[ksanturion10]

Eh, because of the optimisation ofcource . Mine is doing the same with the rear. You have to admit, that the linkage of the XM is more complicated, than onto the Xantia, and as you probably know the corrector has only +/- 1,5 mm of movement through the entire range, so precise calibration is needed here. I think you have misconfigured height corrector linkages, maybe worn parts of it, and to be honest, I'm not really sure, that you have all the needed info at those pages. Maybe Chris knows more about the calibration, and that is why he enjoys smooth, non-complainable ride

[MatPL]

I have recently installed a brand new height corrector on the rear axle and it has not changed anything I have a lot of elements listed and I am sure most of them, but there are also those that I consider suspicious as a power steering rotary valve ...

[ksanturion10]

I have the bad filling, that there are not many people, who are in the possesion of the true know-how, when it comes to the tunning of these devices. It seems, that we will have to employ the old, lenghty method of trial and error. To me, the XM seems overly complicated in comparison with the Xantia, or at least to the non-Hydractive ones.