Workaround for bubbles in LHM return flow

pprado · Post by **pprado** » 17 Jul 2007, 04:17

As AndersDK asked, starting a new thread. I chose to put a more specific subject so we don´t end discussing too much topics about the suspension in one place again...

For those who did not follow the previous thread: We found that the tiny bubbles on the system get recirculated back to the reservoir - and as the output of the return flow on the reservoir is too near from the pump input, the pump sucks then again. That ends up by amplifying the bubble problem. There is some discussion whether the bubbles are generated by frothing on the reservoir fluid surface, or in the return paths.

The idea is to allow the return to flow in the air, over the surface on the reservoir. That way it will at least leave the bubbles on the surface and not near the pump outlet - thus the pump will suck only LHM.

Up to now we have mine (U-tube without return), Simon´s (bypass to the filler cap, temporary to test) and Bernie´s (in-filter U-tube).

On my experience, I saw the click time go from seconds to minuteS, some of the harshness is gone (but I have not done all spheres/cleanings/etc), steering is lighter, car takes at most 4 seconds to turn off the STOP light.

Simon´s Xan already had a good click time that improved; slightly lighter steering; general harshness gone; STOP light up going out in no more than 3 seconds.

Bernie said the ride was improved when he tried his V1 set; he did not told how is V2 yet.

Feel free to edit and correct... just tried to summ up.
Original thread:
http://www.frenchcarforum.co.uk/forum/v ... sc&start=0

Mandrake · Post by **Mandrake** » 17 Jul 2007, 11:33

Yes, I too eagerly await bernies V2 results. So, where are they ?

Regards,
Simon

AndersDK · Post by **AndersDK** » 17 Jul 2007, 15:16

Reader service notification.

Readers who wants the full & exhaustive (!) background story on this issue may take it from here :
http://www.frenchcarforum.co.uk/forum/v ... hp?t=20909
Please do not submit further postings to that thread.

Warning : exhaustive long thread 8)

Post by **CitroJim** » 17 Jul 2007, 20:28

I did a bout of citarobics on my Activa this evening (a job that has been waiting longer than usual due to me not being in the pinkest of health recently but well on the road to recovery now). Out of interest (and because I've never conciously done it before) I watched the LHM in the reservior.

Sitting static at normal height with the engine idling I saw no bubbles at all. From normal to high the top of the reservoir filled with a load of tiny bubbles and the LHM took on a beer-like appearance with a nice head on it. Going from high to low the character of the bubbles changed to those you'd get from washing-up liquid or bubble-bath although no quite so big.

Back to normal from low and the bubbles slowly cleared to leave a nice smooth surface to the LHM with just a few vestigal bubbles around the edge.

I'm still running Hydraflush at the moment so my bubbles my not be typical.

I also noted that I have a weep of LHM from the front Hydractive electrovalve return. In a week it has wept enough to wet the solenoid so it looks like I have considerable and excess leakage past the valve. Due to its somewhat inaccessible position in the Activa I've not yet had a chance to check the pipe or the joint. Irrelevant perhaps to the bubbling issue but them perhaps not. Simon, your thoughts?

jorgy · Post by **jorgy** » 23 Jul 2007, 11:51

It's amazing how much of the "crashiness" goes away when temperature is well past 20C, I've confirmed it again and again. Wonder what on earth is happening to hydraulics. Is it all 4 strut cylinders sliding easier due to metals expanding? Is it LHM becoming less bublly? Is it LHM becoming so much thinner that it passes bettter through otherwise blocked parts of the hydractive blocks? God knows!

George

Mandrake · Post by **Mandrake** » 23 Jul 2007, 12:19

jorgy wrote:It's amazing how much of the "crashiness" goes away when temperature is well past 20C, I've confirmed it again and again. Wonder what on earth is happening to hydraulics. Is it all 4 strut cylinders sliding easier due to metals expanding? Is it LHM becoming less bublly? Is it LHM becoming so much thinner that it passes bettter through otherwise blocked parts of the hydractive blocks? God knows!

George

So you're saying the ride is worse when its cold ?

For me it was the opposite.

Good ride on cold days, poor ride on hot days...

Regards,
Simon

jorgy · Post by **jorgy** » 23 Jul 2007, 13:01

Yes, hot=better. Hmmm...that's not encouraging...

G

bernie · Post by **bernie** » 01 Aug 2007, 13:42

Just got back from a long holiday in Italy
NO rain and 35 to 40c every day 8)

I have a couple of things to say.
My holiday transport was an air suspension coach which has the same floaty Citroen feel and thumps when it hit potholes etc. , all very normal.
Since I've fitted V2 and blead/bleed?? the ha valves the ride has improved and is the same as the coach.
Also prior to my hols, I had a test drive in a new Alfa 147 150TD. Engine and steering were fine but the ride, give me the Xantia HA any day.

My conclusions are that the Xantia system is still good compared to others. I believe we may be chasing our own tails

in trying to improve the ride etc.
Whilst the ride may not be perfect for every road surface, it is after all a compromise.
As I say I believe the ride has improved and I am now satisfied with the ride.

jorgy · Post by **jorgy** » 01 Aug 2007, 15:24

Hi Bernie
sounds like u had a good dose of heat for the winter to come! August 1st today and u can already feel it's coming (at least in Scotland)

As for the ghost chasing: I am definitely sure that I have driven my XM on a total of 2 (two) days over the past 3 years, where the ride was so amazingly unbelievable that instead of going...home, I drove the car all day around without reason, just to feel it ironing every pothole on the road. No thumps at all in any surface whatsoever. Both times it was after an LHM change. Both times it lasted a day. I know it's not remotely as good currently. I whish one day I find the problem and get it to be like those 2 days again. The thing is that, as u observe, a non-working hydractive is already better than a standard car. But u have to have felt it when it's working properly: it's just unbelievable, to the point it makes u feel awkward because it plays with your own learned senses of what to expect to follow when your eyes see a bump, a pothole etc. So, I'd say, *you* would only know if it's "as it should". But what if u have not experienced this state? I' affraid basically the only way to find out is to meet and drive each others cars. Or meet whoever u can near you and see how his car drives.

The news from my side is that I noticed the ride got more "compliant" the last time I drove the car, nearer to what it should be. The difference could be felt even on long indulations on the motorway. This was accompanied by the steering (diravi) being perfected: it now self-returns to the exact center position with an ease I've not seen before; it used to return good in general but you could see it struggling in some moments or it would loose it's centering power just a few degrees before the centre position; this would be typical of worn valves in a high mileage system, but it now centres like a new car I guess. I'm at 1300mls on hydraflush now. Wondering if it's slowly doing something or if the hot weather helped again, but I had not felt the susp so compliant since last Christmas (when other events happened, long story). As the weather looks to be cooling down from now on, I'll soon know the role of the temp.

I also now have bought a new front cylinder and a new rear one, which I'll be fitting when I decide to finish the flushing, around end of August probably.

The car is now in garage for gearbox repair and new exhaust after cat to rear. Then MOT, then I'll be able to budget for more new critical parts -still have to discover what's leacking as to make my regulator click at 13secs; from car history I'm sure it's one of the components connectd to the rear susp-

regards
George

Mandrake · Post by **Mandrake** » 01 Aug 2007, 23:47

bernie wrote:Also prior to my hols, I had a test drive in a new Alfa 147 150TD. Engine and steering were fine but the ride, give me the Xantia HA any day.

My conclusions are that the Xantia system is still good compared to others. I believe we may be chasing our own tails in trying to improve the ride etc.
Whilst the ride may not be perfect for every road surface, it is after all a compromise.
As I say I believe the ride has improved and I am now satisfied with the ride.

Hi Bernie

You have a good point - the overall quality of the ride is so good compared to most cars that the flaws in the ride seem that much more obvious - in particular I find "harsh" bumps like potholes and manhole covers are very obvious compared to the "average" ride quality over most surfaces, such that it seems like there is a problem with the ride.

However get into another car and the bumps that you thought were harsh are no better, and the average ride quality is so much worse.

I think its more a case of certain KINDS of bumps/surfaces simply can't be absorbed smoothly by any suspension system, and the smoother the overall ride is the more you get used to a smooth ride and the more these few annoying types of bumps stand out and seem bad...

Regards,
Simon

Mandrake · Post by **Mandrake** » 02 Aug 2007, 00:01

jorgy wrote:As for the ghost chasing: I am definitely sure that I have driven my XM on a total of 2 (two) days over the past 3 years, where the ride was so amazingly unbelievable that instead of going...home, I drove the car all day around without reason, just to feel it ironing every pothole on the road. No thumps at all in any surface whatsoever. Both times it was after an LHM change. Both times it lasted a day. I know it's not remotely as good currently. I whish one day I find the problem and get it to be like those 2 days again. The thing is that, as u observe, a non-working hydractive is already better than a standard car. But u have to have felt it when it's working properly: it's just unbelievable, to the point it makes u feel awkward because it plays with your own learned senses of what to expect to follow when your eyes see a bump, a pothole etc. So, I'd say, *you* would only know if it's "as it should". But what if u have not experienced this state? I' affraid basically the only way to find out is to meet and drive each others cars. Or meet whoever u can near you and see how his car drives.

I am SO with you there! I have also experienced the super magic carpet ride many times now, where the ride is just SO good compared to normal, that you just want to keep driving and try driving over all the familiar pieces of road you drive over because its just so damn good, and the car is so enjoyable to drive in that state.

After you have experienced that ride, you are disapointed by the "normal" ride that you usually get.

And thinking back, it has been after various work has been done on the suspension, and in all cases it involved either the LHM being changed, or the suspension being fully depressurized, or Citrerobics being done.

One thing that sticks in my mind too, is that quite often, the best result was when the car was depressurized with the front of the car up on wheel ramps - with the car on about a 20 degree angle. I would depressurize the car, do some work, repressurize it, and go for a drive, and the ride would be fanastic, for a while anyway. Why ? I don't know...perhaps the angle affects the flow of bubbles from the return to the inlet in the tank ?

The news from my side is that I noticed the ride got more "compliant" the last time I drove the car, nearer to what it should be. The difference could be felt even on long indulations on the motorway. This was accompanied by the steering (diravi) being perfected: it now self-returns to the exact center position with an ease I've not seen before; it used to return good in general but you could see it struggling in some moments or it would loose it's centering power just a few degrees before the centre position; this would be typical of worn valves in a high mileage system, but it now centres like a new car I guess. I'm at 1300mls on hydraflush now. Wondering if it's slowly doing something or if the hot weather helped again, but I had not felt the susp so compliant since last Christmas (when other events happened, long story). As the weather looks to be cooling down from now on, I'll soon know the role of the temp.

So you've done a mod similar to bernies have you ?

I'm still yet to obtain a suitable piece of concertina plastic tube. I still have the pipe going through the top of the tank, but I have noticed the ride has deteriorated somewhat in the last week. It is still a LOT better on average than before, but has the occasional day where the ride is not as good as it should be.

This is probably not surprising when I have the pipe just going straight in the top of the tank, bypassing the return filter altogether. I think one thing that may be happening in this situation is that when the engine revs are low and the flow rate returning is low, everything is fine, but when the engine is reving harder, the flow rate increates, and probably starts becoming turbulent in the tank, and bubbles may be circulating in the tank and still getting into the intake.

I can't wait until I can get the time to find a suitable piece of tube and fit it inside the filter...

Regards,
Simon

pprado · Post by **pprado** » 02 Aug 2007, 00:08

I´ve had REALLY good ride in few situations after I bought the car...
One of them was when the brake valve started coloring my carpet :-/

Done on warranty... when I went to get the car, the ride was so amazing I completely forgot the problem with the brakes!

What´s the procedure the dealers need to do? Maybe they always bleed the brakes when they do any maintenance?

Hey Simon, try moving the tube so it gets nearer a wall... I think that can help

Mandrake · Post by **Mandrake** » 02 Aug 2007, 01:47

pprado wrote:I´ve had REALLY good ride in few situations after I bought the car...
One of them was when the brake valve started coloring my carpet :-/

Done on warranty... when I went to get the car, the ride was so amazing I completely forgot the problem with the brakes!

What´s the procedure the dealers need to do? Maybe they always bleed the brakes when they do any maintenance?

Well if they replaced the brake doseur valve that would require a full depressurization of the hydraulic system - both suspension, and pressure regulator, as it is connected to both the main supply pressure for front brakes, and the rear suspension for rear brakes.

They probably bled the brakes afterwards too, although I doubt that would have any effect on the ride.

So my guess is it was the full depressurization that gave the temporary good ride - I have had the same effect many times before.

Hey Simon, try moving the tube so it gets nearer a wall... I think that can help

The way its attached I can't really move it...I think I'll just find the appropriate piece of plastic tubing and change it over.

Regards,
Simon

jorgy · Post by **jorgy** » 02 Aug 2007, 01:57

Hi all

Simon, no I haven't touched the LHM tank, only differences I can think of are 1/ambient temp, 2/miles on hydraflush clock up. I first want to correct the fault that makes my clicking being 13secs (totally unacceptable). I (want to) believe this will be related to the crashiness.

Pedro, interesting u have had a new brake valve as a worn one is a prime suspect for "foaming" the LHM, so it seems it's not related...Hmmmm...what if it happens that our systems are contaminated with something that makes the LHM work not-well soon after u put it in? That's another possibility along with the "bubbles". Because it is strange that this harshness problem seems to affect a number of cars but not others -and it doens't seem related to age, mileage-. Something specific must be happening in our cars. Personally I don't know my car's history...has somebody maybe used brake fluid sometime? I ll never know.

I know I m not being any original, but all shows the "after-hydraulic-work" effect on our hydraulic cars...Mind u, for a year or so I used to think of the scenario that it was air in the LHM that *makes* the super-softness effect. This was because, just after putting all new spheres, ride was lovely (this was 1 of the days). The next morning I went first thing and bled the brakes to complete the work -I had already spent a year chassing the pressure range that the p.reg. is supposed to produce and had measured and corrected it to 145-170 bar, so that I can be sure the middle spheres open well-. So very happy I completed the bleeding and took the car for a drive, and the ride was not-so-soft again...misery!! I then thought: "perhaps my brake valve has a leack> the leack will make again the middle spheres not open up properly, due to system pressure being not strong enough> when doing hydraulic work, air gets into the system and self-bleeds, except brakes> perhaps air trapped in the brake valve has blocked the LHM's way to the leacking point> now I've bled the air from the brakes, the via to the leacking point is again open and system pressure is again not sufficient". Anyway, this was the scenario I was reflecting on for about a year. It's a shame I had not taken the car for a ride before I bleed the brakes that morning, I'd have known immediately if it had anything to do with...

But I'm optimistic by end of September I'll find the problem. I'll have changed/tuned so many parts of the system by then.

regards
George

jorgy · Post by **jorgy** » 02 Aug 2007, 12:39

Hi all

someone here said that there's a bleeding nipple on the hydractive blocks of the HII cars. As much as I look on one, I can't see a bleeding nipple. Any ideas??

George

ps. looking at the document "RegulateurHydractive.pdf" at

http://fr.groups.yahoo.com/group/activa ... uspension/