Air bubbles in the LHM gives harsh ride?

steelcityuk · Post by **steelcityuk** » 11 Dec 2006, 08:13

Following on from my posts in a previous thread with regard to testing the Hydractive system, I've now replaced the LHM feed to the pump with clear pipe (I've also fitted a small piece of clear pipe to the main LHM return). If I shine a torch through the pipe I can see that the LHM is 'full' of tiny air bubbles. This can't be right, can it? I don't see how they are getting there unless the reservoir top is cracked or faulty in some other way. Electrically the Hydractive system seem to be doing what it should and when stationary the suspension is soft and easy to compress when in soft mode but is very firm when the Hydractive valves close after turning off the engine.

Any experience of this?

Steve.

Homer · Post by **Homer** » 11 Dec 2006, 08:34

Are the air bubbles on the feed or the return?

If it's the return then it may be nothing to worry about or may be an internal leak on a sphere.

If it is the feed then it suggests the feed pipe has a leak and is sucking air in.

Mandrake · Post by **Mandrake** » 11 Dec 2006, 08:36

steelcityuk wrote:Following on from my posts in a previous thread with regard to testing the Hydractive system, I've now replaced the LHM feed to the pump with clear pipe (I've also fitted a small piece of clear pipe to the main LHM return). If I shine a torch through the pipe I can see that the LHM is 'full' of tiny air bubbles.

Which pipe do you see the bubbles in ? The one going to the pump, or the return pipe ?

This can't be right, can it? I don't see how they are getting there unless the reservoir top is cracked or faulty in some other way.

I have the same problem - but only intermitantly. I also can't figure out how they get in either.... there is a bung with an o-ring on it in the inlet path that could leak:

http://homepages.igrin.co.nz/simon/imag ... t-plug.jpg

But I've replaced the o-ring on mine and it didn't help. The point at which the hose attaches to the leadoff pipes on the tank is another possibility, but I've checked that on mine too... the plastic riser inside the tank is also ok....

Electrically the Hydractive system seem to be doing what it should and when stationary the suspension is soft and easy to compress when in soft mode but is very firm when the Hydractive valves close after turning off the engine.

Ok well air bubbles wont have much effect on a bounce test like this - how stiff it is in the hard mode is determined by the outer (strut) spheres... and because the damping valves are tuned so stiffly (by Citroen standards) even when those spheres are good it can seem like its "too stiff".

Just pressing by hand can barely open the threshold (damper) valves of the hard mode, so the oil is just flowing through the very tiny bypass holes, and therefore feels very stiff - but when you hit a bump during driving the valves can open.

Unless you're really familar with how the suspension should feel (to a bounce test) with good spheres or you have a pressure tester to actually test the spheres, you could be chasing ghosts...

Regards,
Simon

steelcityuk · Post by **steelcityuk** » 11 Dec 2006, 11:45

Hi,

Just to clarify the situation - initially I fiited a liitle bit of clear pipe in the return pipe. This was showing tiny air bubbles so I went further and replaced the entire pump feed with a new piece of clear piping and used new 'jubilee' clips to ensure a tight fit.

I assumed that because the Hydractive ECU is working as it should (at least according to the LED I've fitted) and the suspension is soft or hard when it should be when stationary the the fault must be down to some other factor such as air in the LHM. All spheres changed this Autumn.

Any ideas as to what to check next? Could such tiny bubbles cause this problem?

Steve.

steelcityuk · Post by **steelcityuk** » 11 Dec 2006, 12:03

I'm a bit puzzled following the picture of the bung in LHM tank. I thought that the pickup pipe would be moulded straight down into the bottom of the tank and yet it doesn't seem that way. Is this a method of bleeding out any air bubbles? I may try taking a line from the pump through this bung hole and into the tank directly and see what effect that has.

Steve.

citronut · Post by **citronut** » 11 Dec 2006, 13:32

no as the tank is not desined to be air tight,also you might expect to see some air in the return and froth in the tank as there is a high volume of fluid returning to the tank all the time the engine is running
regards malcolm

bernie · Post by **bernie** » 11 Dec 2006, 13:47

Been there for a while now, Steve as Simon knows
Exactly the same symptoms as you.
So far I've replaced with new
both H/C's
both HA valves
all 8 spheres
Total LHM after rinse
pump

I've also tried s/h HA blocks and a s/h ECU.

Also bleeding the HA block nipples (Series 2 only) had no effect because the air was constantly coming out.

About a year ago I fitted clear pipes to and from the LHM tank and discoved the foamy bubbles coming OUT of the tank.
I glued and sealed the cap on the outlet, I removed the filters and also tried the pump inlet straight into the tank.
Same result in all cases, bubbles still going into the system.
I've come to the conclusion, after seeing inside the tank, that the LHM returns under so much force that it foams up. This foam is then sucked back into the system via the pump.
A possible solution would be a BIGGER tank allowing the LHM bubbles to settle.
I do feel that the air in the system is the problem.

jeremy · Post by **jeremy** » 11 Dec 2006, 14:00

Presumably the forcible return is from the power steering - so an intermediate settlement tank for it might help.

Presumably this system worked OK when the car was new - so what's different now?

steelcityuk · Post by **steelcityuk** » 11 Dec 2006, 14:12

I've just been for a look around the Xantia-L forum on Yahoo groups and it seems that I should have a dash light for the Hydractive system. I've never seen one on start up so that makes me think a bulb has gone seeing as the diagnostic LED says it's working as it should.

It sounds as if these air bubbles are a common thing. I know they are extremely small - you can't see them without a torch - but if they are making up 10-20% volume of the LHM then that's gonna be a problem isn't it? I also suppose that once air bubbles are in the liquid it would take quite a while for them to dissipate. Maybe they are being introduced by a leaking pump. I'm thinking this way because parts of the pump must be at low pressure and/or vacuum so a faulty seal here would suck in air and so on. I think a trip to the breakers is needed. Could this also be the reason for rapid regulator cycling?

Steve.

steelcityuk · Post by **steelcityuk** » 11 Dec 2006, 14:42

Having gone back over previous postings for harsh ride, it seems that the main link is the fluid. There's quite a few postings where owners have reported a much improved ride for a short while after replacing the LHM or after replacing parts followed by replacing 'lost' LHM. Is this the time it takes for the LHM to become aerated and so spoiling the ride?

If this is the case could it be proved by replacing all the LHM you can in one go then taking it for a test drive?

Has any owner taken their car to a dealer for fixing and got a result?

Steve.

bernie · Post by **bernie** » 11 Dec 2006, 15:07

jeremy wrote:Presumably the forcible return is from the power steering - so an intermediate settlement tank for it might help.

Presumably this system worked OK when the car was new - so what's different now?

That's the 64 million dollar question, Jeremy, what has changed?

bernie · Post by **bernie** » 11 Dec 2006, 15:12

steelcityuk wrote:I've just been for a look around the Xantia-L forum on Yahoo groups and it seems that I should have a dash light for the Hydractive system. I've never seen one on start up so that makes me think a bulb has gone seeing as the diagnostic LED says it's working as it should.

As it's an Exclusive the HA warning lamp will be on the switch to the right of the steering wheel

It sounds as if these air bubbles are a common thing. I know they are extremely small - you can't see them without a torch - but if they are making up 10-20% volume of the LHM then that's gonna be a problem isn't it? I also suppose that once air bubbles are in the liquid it would take quite a while for them to dissipate. Maybe they are being introduced by a leaking pump. I'm thinking this way because parts of the pump must be at low pressure and/or vacuum so a faulty seal here would suck in air and so on. I think a trip to the breakers is needed. Could this also be the reason for rapid regulator cycling?

I have already tried a new (recon) pump from GSF with no difference, if that saves a little effort and money

Steve.

jeremy · Post by **jeremy** » 11 Dec 2006, 15:16

Liquids are non-compressible - but liquid/air mix must be compressible. Wouldn't this give a softer, rather uncontrolled ride?

In fact the various valves may act as filters - passing air but not LHM.

If the system is cycling frequently - check the basics first - starting with the accumulator sphere - which usually can be tested by sitting in the boot after turning off the engine. (back should sink a long way - then rise again after 30 seconds - powered by the accumulator.) The cycling should also slow if the car is raised fully as the height correctors will be open and the suspension spheres will function as accumulators.

steelcityuk · Post by **steelcityuk** » 11 Dec 2006, 15:19

Hi Bernie,

I did notice that after I re-read your post. Sorry.

Could it be down to the brand of LHM? Are they all the same? Are other owners using Total LHM? I'm not could that be the problem or am I chasing ghosts?

Steve.

bernie · Post by **bernie** » 11 Dec 2006, 15:31

steelcityuk wrote:Hi Bernie,

I did notice that after I re-read your post. Sorry.

Could it be down to the brand of LHM? Are they all the same? Are other owners using Total LHM? I'm not could that be the problem or am I chasing ghosts?

Steve.

I have only used Total LHM just in case it was a problem

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Air bubbles in the LHM gives harsh ride?

Air bubbles in the LHM gives harsh ride?

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