Air bubbles in the LHM gives harsh ride?

[bernie]

Another pointer I discovered a long while ago: the facelift (mk2) Xantia HA2 system has bleed nipples on the HA blocks front and rear whilst the mk1 system does not.
On the advise of my local Citroen dealer I opened them up with a suitable pipe back to the tank. Result: air bubbles continueously came out, they would not stop

[JohnCKL]

(The hydractive pipe from the left strut has become unattached from its clamp on the inner body wing, AND I've discovered the two rubber insulated clamps along that pipe to the left of and in front of the battery are both MISSING the bolts that are supposed to secure them, thus allowing the pipe to chatter against the body. Evil or Very Mad )

Same problem I had, whenever I turned, there's always a sound, after getting the clamps from breakers and bolting down the pipes, stopped the clanking.

dishwasher rinse-aid, wouldn't that cause corrosion to the inner metals of the LHM system, esp if its water based? Its alkaline and should cause corrosion. There is some sort of anti-foaming agent used in the formulation for dishwasher and other applications. Those in the chemical business should get a hold of that and try it.

[Mandrake]

Another pointer I discovered a long while ago: the facelift (mk2) Xantia HA2 system has bleed nipples on the HA blocks front and rear whilst the mk1 system does not.
On the advise of my local Citroen dealer I opened them up with a suitable pipe back to the tank. Result: air bubbles continueously came out, they would not stop

Good point bernie,

On the Mk1 Xantia's you can't bleed the supply line for the electrovalve (which is relatively long) so if there have been problems with "airated" oil being fed to it, even after that problem is solved, it would probably take several hundred on/off actuations of the electrovalve to purge that line of air, as each activation takes such a tiny amount of oil. (Translation: things may slowly improve now over the next week )

Of course a leaky electrovalve would purge much faster...

It seems likely to me that large quantities of air in that supply line to the electrovalve would probably cause the valve to malfunction in unpredictable ways, and certainly wouldn't aid the cause of getting smooth a ride...

Regards,
Simon

[Mandrake]

(The hydractive pipe from the left strut has become unattached from its clamp on the inner body wing, AND I've discovered the two rubber insulated clamps along that pipe to the left of and in front of the battery are both MISSING the bolts that are supposed to secure them, thus allowing the pipe to chatter against the body. Evil or Very Mad )

Same problem I had, whenever I turned, there's always a sound, after getting the clamps from breakers and bolting down the pipes, stopped the clanking.

Do you mean the side wing clamp, or the rubber clamps or both ? On the sidewing clamps the original bolt is a self tapper and the one on the left was missing when I got the car, and I've just noticed the one on the right wing has "popped" out and disappeared in the last week as well...

Why they used a self tapper into a body panel to hold a pipe that needs be clamped pretty darn securely and is under a lot of strain I don't know.

What did you replace the bolt with ? I managed to get a nut and bolt in there with extreme difficulty some time ago (access holes are quite far from the bolt) but even with the clamp fully squeezed its no longer gripping on the metal flange on the pipe... I was thinking of slipping a bit of thin copper stripping in there as a gasket to build up the diameter ?

Any suggestions of a better type/size of bolt that can be easily fitted to the wing but be secure ? The hole is too streched for another self tapper, perhaps a spire nut and bolt combination ?

Regards,
Simon

[Mandrake]

Recently, I hydraflushed my Activa and cleaned the filters. they were incredibly dirty and near to being totally choked. The difference has been quite spectacular and I'm seeing all the same results as you Simon and Pedro For an Activa, the ride is really quite pleasant.

What is more, it seems to be holding. I have about 300 miles to run before I drain the Hydraflush and refill with Total LHM. It will be interesting to see if the effects last.

So maybe activas don't ride so badly after all ?

Bear in mind that the more volume of oil traveling around in the active (ride influencing) part of the suspension, the more potential for air to build up and interfere with the ride - Hydractive 2 has the two large pipes from the struts to the HA2 block at both ends of the car that a standard model doesnt have, the Activa has an additional 10mm pipe loop for the anti-roll rams that travels from the front to the back of the car! What happens if these pipes connected to the anti-roll rams get full of air bubbles too ? Can't be a good thing!

Keep us posted on the ride Jim.

Regards,
Simon

[Mandrake]

You didn't mention if the clicks got improvement... however on mine they did.

Thats because my accumulator cycle time has been pretty good most of the time, typically a minute or more, although lately I had been noticing that SOMETIMES the cycle time was quite short for a few cycles and then longer again.

I think you'll find that very short cycle times can't be directly caused by the air (I could be wrong though) - but maybe indirectly by affecting the leakage rate of some component in the system.

The most common cause of intermitant wildly varying cycle times on HA2 models is one or more electrovalves which have intermitant leakage - when they start playing up you'll find that every time they switch on and off the amount of leakage is random - sometimes they will leak a lot, sometimes a little, sometimes not at all, then next time they switch it will change again.

This happened to me with a faulty front electrovalve, it got so leaky at one point regulator cycle time was down to 8 seconds and you could hear a hissing coming from the valve!

After taking the valve apart after replacing it I found all that was wrong with it was a TINY imperfection/pit on the tapered needle that forms half of the needle valve.....

Regards,
Simon

[xantia_v6]

I agree with the general thrust of this thread, that air suspended in the LHM will cause degraded suspension, and that it is difficult to de-aerate the oil when the storage tank is small relative to the circulation rate.

But I have a problem accepting that it is normal for air to be entering the system. As I understand it, the entire hycraulic system is hermetically sealed, except for the top surface of the oil in the tank.

Any air that was in the system when it was filled would work itself out, due to the action of bubbles rising in the tank. So where can significant quantities of air get into the system?

It must be on the inlet side of the pump, as all of the other pipes and fittings (including the return pipes) are under positive pressure, because they should be full of oil and are below the tank.

We know that the feed pipe from the tank to the pump can get air leaks, but this is easily fixable. Maybe the (worn?) pump can suck in air around the shaft seal. Can the outlet pipe from the tank be sucking air due to the fluid level being low it its vicinity?

[Mandrake]

I agree with the general thrust of this thread, that air suspended in the LHM will cause degraded suspension, and that it is difficult to de-aerate the oil when the storage tank is small relative to the circulation rate.

The circulation rate isn't nearly as much as I thought it would be - when doing the above testing I ran it for a short time with the return pipe held over the filler hole - and at idling speed it was much less than you'd get from a standard water tap. (It's about 4cc per revolution of the pump counting steering and suspension outputs)

But I have a problem accepting that it is normal for air to be entering the system. As I understand it, the entire hycraulic system is hermetically sealed, except for the top surface of the oil in the tank.

It's not normal for air to be entering the system - thats the whole point of this problem...

Yes, when the car is nice and new in theory it should be hermetically sealed, including the return systems, but the return lines are mostly rubber and plastic, with lots of little elbow joints, press on joints, etc, which all perish with age.

Any air that was in the system when it was filled would work itself out, due to the action of bubbles rising in the tank.

Assuming that more bubbles werent getting in at a greater rate than what they can disperse

So where can significant quantities of air get into the system?

It must be on the inlet side of the pump, as all of the other pipes and fittings (including the return pipes) are under positive pressure, because they should be full of oil and are below the tank.

See my previous post on why this may not be so...

Oil has surface tension and small cracks where pipes join can easily allow air to be sucked in when there is a flow of oil to pull it in, but not leak outwards when the flow stops. (There is no pressure in many of the return lines, just the weight of the oil)

We know that the feed pipe from the tank to the pump can get air leaks, but this is easily fixable. Maybe the (worn?) pump can suck in air around the shaft seal. Can the outlet pipe from the tank be sucking air due to the fluid level being low it its vicinity?

You seem to be a bit late to the party because although what you're suggesting is perfectly logical, those of us that have had this problem have already been down this exact path. I've replaced the inlet hose to the pump AND the pump on my car.

Yes there was some improvement but the basic problem remained...

When you eliminate the probable, all that remains is the improbable.

As an update - this morning the stop light went out after 3 seconds and the car was up to height in 20 seconds, much faster than it has been for a long time. Ride was still good on the way to work...

Regards,
Simon

[bernie]

Another pointer I discovered a long while ago: the facelift (mk2) Xantia HA2 system has bleed nipples on the HA blocks front and rear whilst the mk1 system does not.
On the advise of my local Citroen dealer I opened them up with a suitable pipe back to the tank. Result: air bubbles continueously came out, they would not stop

Good point bernie,
Regards,
Simon

I bet the fitting of bleed nipples was a developement that overcame this problem on 4 year old VSX's

[bernie]

Here's what I've come up with

[JohnCKL]

Do you mean the side wing clamp, or the rubber clamps or both ? On the sidewing clamps the original bolt is a self tapper and the one on the left was missing when I got the car, and I've just noticed the one on the right wing has "popped" out and disappeared in the last week as well... Evil or Very Mad

The bolt "leg" was broken, can't mount into the side square hole. Got the whole set from breakers and mounted it. If the hole is too stretched, then the original bolt can't be fixed. Have to get around it with another setup. Removing the signal lights and some wiring harness can access the holes easier.

[pprado]

Thanks for everyone encouraging!

This thread is responsible for the experiences. Based on this one I had a talk with a friend here (who by the way knows about viscosity, superficial tension, etc) who explained that air on the system would REALLY make the ride worse.

Based on that I started my fight against bubbles...

Hey Bernie, what a nice idea! I'm only not sure if there is enough space on the end of the downpipe to fit that curve...

Tell us how it looks for you!

BTW, on my car I've got short clicks again yesterday what suggests I have some component leaking - and as it is intermittent it can be the HA valves.
Today it is long again. Almost no bubbles on the return pipe.

Hope we are on the right path 8)

[Mandrake]

Here's what I've come up with

Whats that pipe from ?

I presume you'll have to trim the ends a bit shorter than that or there will be no room for the oil to exit between the end of the pipe and the top of the housing ? I guess the length you want is so the pipe is just sticking above the oil level when the suspension is down ? (Maximum oil level in the tank)

A progress report on my car - the ride has deteriorated a bit, but is still relatively good, and seems to have stabalized. I still havn't fixed the unsecured Hydractive pipes yet, (poor weather) so that may contribute.

Stop light going out time is still short - about 3 seconds after the car stands for 8 hours, or 5 seconds after it stands over night. Before this experiment it was around 15 seconds.

I'm not convinced that my pipe through the top hole arrangement is completely preventing the bubbles recirculating - because its angling down, if the flow velocity is high enough (as it would be at higher engine revs) then it may be causing a column of circulating oil, so I like the idea of the U shaped tube a lot better.

Can anyone tell me what diameter and length the the return pipe of the tank top is that we are trying to slip the U-tube over ?

Regards,
Simon


Regards,
Simon

[bernie]

Thanks for everyone encouraging!



Hey Bernie, what a nice idea! I'm only not sure if there is enough space on the end of the downpipe to fit that curve...

Yes there is enough room

[bernie]

Whats that pipe from ?

I presume you'll have to trim the ends a bit shorter than that or there will be no room for the oil to exit between the end of the pipe and the top of the housing ? I guess the length you want is so the pipe is just sticking above the oil level when the suspension is down ? (Maximum oil level in the tank)

Regards,
Simon


Regards,
Simon

The pipe comes from a DIY air con unit I fitted in my bedroom. It's for the waste water from the evapourator.

Unfortunatly it's just too small ID. It fits over the spigot about 25mm because the spigot has compressedwith the split in it. I could not push it on anymore so have taped up the rest of the split.
The other end I shortened to just below the filter height as I did not want blow back up the incoming returns.
So far no leaks from the top of the tank and the foaming inside the tank has stopped.
The ride has inproved but I have not bleed the HA blocks yet