extra Baffle in tank?

[froggy]

Hi, I have just read in the August edition of "Citroenian", that a Xantia owner had used a piece of flexi pipe to make a second baffle in their LHM tank . He had aerated LHM being pumped into the system , thus he found it full of little bubbles (Ditto) .the thought was that the highly pressured , elastic bubbles of air were causing shock waves in the LHM. as the suspension strut strikes bumps, it amplifies the shocks making a bad ride quality. The flexi hose allows the hydraulic pump to draw less turbulent LHM from the tank. any thoughts anyone ? This mirrors my ride quality ! I have changed spheres , LHM, cleaned filters and so on.....! cheers Terry.

[Hell Razor5543]

This might be worth a look;

http://www.frenchcarforum.co.uk/forum/v ... minute+mod" onclick="window.open(this.href);return false;

[Mandrake]

That reminds me, I must do that mod to my new Xantia...

[Old-Guy]

I'll dare to stick my head above the parapet. Someone will be along shortly to take a pot-shot!

To my mind the $64,000 question is, "From whence cometh the 'air' in the LHM?" Either one or more spheres leaking nitrogen into the system, or air being sucked into the HP pump pipe. The latter seems to be a common problem for a combination of reasons:
1. The joint between the pick-up in the plastic reservoir-head and the flexible feed pipe to the pump is at the highest point - the point of greatest negative pressure - so the slightest leak here will cause air (many, many times less viscous than LHM) to get sucked in.
2. The pump has to suck LHM up out of the reservoir through a very fine filter that restricts the flow of the relatively viscous LHM thus adding a negative dynamic pressure to the negative static pressure. The addition will be very considerable when the filter is dirty and the PAS requires large volumes of LHM.
3. The 'rubber' pick-up pipe gets stretched and hardens with age so it's likely to leak after being disturbed.
4. The pick-up filter is easily missed and rarely cleaned (on all 4 Xantia estates that I've worked on, ALL had filthy pickup filters when I checked). I swear one hadn't been cleaned in 100,000+ miles!

By treating the symptoms not the disease, modifications to the reservoir/pick-up will ultimately prove to be a waste of time and energy.

Trying to fix a persistent air leak in the low-pressure side of the Green Lady's fuel system, I recently had a bright idea: degrease any suspect joint/pipe with brake-cleaner, then smear with Hylomar and immediately start engine. This worked a treat on my home-made blind stub on the injector leak-off chain.

If I had reason to think that all the spheres ought to be sound, my first modification would be to undo the hose-clip on the joint (at 1 above) pull the pipe gently away from the reservoir until it's starting to stick on the nipple of the plastic stub, degrease end of pipe and plastic stub (clean petrol would do), smear Hylomar into crack between stub and flexible pipe all the way round, push pipe in opposite direction until it binds, check that there's a seal of Hylomar all round the joint, the do up the hose clip (gently bif it's a jubilee clip). The only long-term solution is a new pipe.

[Mandrake]

I'll dare to stick my head above the parapet.

You are of course entitled to your own opinion Guy, and while I don't disagree with many of your points, you have oversimplified the situation. It is not as simple and clear cut as you seem to believe. The questions you pose have also already been discussed and debated in great detail in previous threads over many years.

I agree that the pipe from the tank to the pump inlet is usually the first suspect when air is getting into the system and causing a harsh ride. I think everyone can agree on that one for all the reasons you describe, including the fact that the joint above the tank is under a slight vacuum. There is also a small o-ring that seals that joint at the top of the tank, and if that leaks it would have the same effect. I also agree that a clogged filter would make any small air leak much more prominent.

Where we part ways is your assertion that only the inlet pipe can cause this issue. This is simply not true.

Case in point was my 1997 S1 Xantia that I owned in NZ - this was the car that probably started the whole air bubbles in the suspension debate. The suspension problems on that car were discussed and debated ad-nauseum nearly 10 years ago. Some of the threads were lost unfortunately but a couple remain on the forum.

I went over the suspension on that car with a fine tooth comb trying to solve its intermittent very harsh crashy ride. On a bad day the ride was simply awful. On a good day the ride was fantastically good. Everything you list (and more) was done. The car was driven for almost a year with a section of clear hose tapped into the RETURN line to the tank, as below:



This was done to troubleshoot the appearance of the bubbles to try to work out when and why they were occurring. There were large quantities of air bubbles on the RETURN line going back into the tank. Because of the design of the tank header the return and inlet are fairly close together with insufficient "de-aeration" ability for the high flow rates involved. A small amount of returning air bubbles will be caught inside the return filter and percolate to the top harmlessly but a large number of bubbles overwhelm the filter, pass through the filter and are immediately sucked back into the pump.

The inlet pipe from the tank to the pump was completely replaced with a new high quality custom fit pipe, and I was VERY careful to make sure it was sealing at both ends. It did not fix it.

The hydraulic pump had its seals renewed, this did not fix it. I swapped in another different hydraulic pump, this did not fix it. All accessible return line joints were checked. The car had also had a replaced electrovalve, new spheres (of course) both height correctors overhauled and lubed, LHM change, filters cleaned, etc. It even had the rear suspension arm bearings AND the front strut rams replaced. No stone was left unturned.

Still the intermittent harsh ride persisted, and still the large quantities of air bubbles returning to the tank persisted. The only thing that made any improvement to the situation was the U-tube that I inserted inside the return filter to direct the returning flow away from the inlet. In hindsight after performing the "10 minute mod" to my next Xantia, I believe the simple modification of cutting the return pipe in the header shorter is more effective than the U-tube.

So what is the source of the bubbles ? I believe it is the cumulative effect of lots of aged/hardened, very slightly leaky low pressure return lines. With enough of a poor seal that they can suck in air when the oil flows, but not have enough of a leak to leak LHM (with its much higher surface tension) when it's not flowing. The biggest candidates are probably the large rubber return hose from the pressure regulator to the tank AND the rubber return hose from the PAS rack. In hindsight I suspect the PAS rack hose might have been the main culprit on that car.

The point is though, the leaks may in reality be a number of small leaks combined which are nearly impossible to fix, short of replacing ALL rubber return lines, which clearly isn't practical. Another factor is that the tank design is poor such that the high flow rate causes aeration of the oil in the tank itself, no amount of leak fixing will solve that.

Redirecting the flow where it returns inside the tank to both (a) reduce the aeration happening inside the tank and (b) divert the incoming flow as far away from the inlet for the pump (bottom of the cone shaped filter) is a simple and practical solution to the problem.

On the Silver problem child V6 that simple fix was extremely effective - the intermittent harsh ride disappeared completely for months without a single re-occurrence, it only started getting harsh again when the inlet pipe started to leak. In just a few weeks the ride got so harsh and uncomfortable that I was sure the spheres were shot but after fixing the leaking pipe the ride was back to normal again.

There is absolutely no doubt that air bubbles being pumped into the suspension can cause harsh ride, unfortunately there isn't just one cause and one solution for the problem. The "10 minute mod" is something suggested if all other avenues have been ruled out and the problem remains - on those stubborn cars I suspect its a case of lots of small air leaks on the various return lines around the car.

[Old-Guy]

Simon, I don't disagree one whit with your analysis based on far greater experience.

I know the subject has been extensively debated and analysed over the last umpteen years (and I'm a relative newby), nonetheless I stick by my original comment the the first thing I'd look at was the joint in the inlet/pick-up pipe. I perhaps should also have said, "after cleaning the filters".

I didn't intend to imply that the pick-up pipe is the only suspect.

I know only too well that finding air leaks can be a nightmare: I'm once again hunting air ingress on the LP side of the Green Lady's fuel system. I've replaced all those for which standard fuel pipe can be used. Various major pipes are NFP and the current prime suspect (one-piece pipe from bulb to filter) is nothing like the 3-piece set shown on service.citroen for her VIN. The next easy swap-out is the priming bulb for a much younger one (which I'll test for air leaks first). If the local forecast for tomorrow is still dry, I'll try that.

[DickieG]

From personal experience take it from me you'll be chasing shadows and the only improvement you'll see will be the placebo effect, a member called "Bernie" looked into the bubbles from the return line and fitted a "U" bend to the return line of his black Exclusive estate with the intention of ensuring the bubbles were deposited above the pump inlet line. I later bought Bernie's car complete with the modification still in place, take it from me the car rode no better to any other Hydractive Xantia I owned at the time (I owned quite a number during that period so I could compare cars back to back), my gold VSX had by quite some distance the best ride of any Xantia I ever experienced.

If the problem existed and could be cured with a very simple and cheap modification to a pipe, something tells me Mr Citroen might well have carried out the modification himself.

[Mandrake]

From personal experience take it from me you'll be chasing shadows and the only improvement you'll see will be the placebo effect, a member called "Bernie" looked into the bubbles from the return line and fitted a "U" bend to the return line of his black Exclusive estate with the intention of ensuring the bubbles were deposited above the pump inlet line. I later bought Bernie's car complete with the modification still in place, take it from me the car rode no better to any other Hydractive Xantia I owned at the time (I owned quite a number during that period so I could compare cars back to back), my gold VSX had by quite some distance the best ride of any Xantia I ever experienced.

Sigh. This again ? If I didn't know better I would think you were trolling Mr DickieG...

What you're basically saying can be summarised as "it didn't make any difference for me, therefore its just a placebo and the problem itself doesn't even exist and is therefore all in your head" which I find quite insulting and condescending especially when this is the second or possibly third time around you've made this same assertion, almost word for word. (One need only look in the 10 minute mod thread to see your previous attempt to muddy the waters on this issue)

I can't speak for Bernie or his car but I know what I have seen first hand now with success on TWO different cars, soon to be a third. The first car was never completely cured but was vastly improved such that symptoms were minimal and infrequent, the 2nd car (Silver V6) was completely cured after more than a year of ongoing intermittent harsh ride.

Nobody has ever said that all Xantia's are afflicted, nobody has ever said that a modification such as this gives a better ride than a NORMAL properly functioning Xantia. There is no reason for you to expect a modified car to ride better than one that is already working properly, and to suggest that a failure for one modified car to ride better than all your other Xantia's means that it does nothing is simply ludicrous and nonsensical.

If the problem existed and could be cured with a very simple and cheap modification to a pipe, something tells me Mr Citroen might well have carried out the modification himself, sometimes when looking at theories you can discover problems that don't actually exist then look for reasons to justify hours of work which is where the placebo effect comes into play.

Really ? So Mr Citroen would never make a design mistake that only rears its head after a car is 10 years or so old and well out of warranty when they have no longer any liability or need to care ? Do I need to remind you of the design flaws that everyone knows about in the Xantia such as the strut tops ? They have not one, but two major failure modes that cause unreasonable and catastrophic failure - rusting of the inadequately rust protected mounting frame in salty countries like the UK, and rubber cracking/shear/separation failure in hot humid countries. Either way the result is a speared bonnet and collapsed suspension.

My own mums Xantia 1.9TD has this happen to it and it resulted in an otherwise perfectly good car being scrapped. Fortunately it happened to her during reversing and not at speed. Yet Citroen didn't care, no recall was ever done (arguably it should have been) and the revised strut designs were quietly slipstreamed into the replacement parts channel with no admission of liability. If they can make a mistake as big as designing a strut that was inherently prone to catastrophic failure its not a huge stretch to suggest that they could make a mistake in the design of the header unit in the hydraulic tank that only became apparent when pipes got old and leaky with age ? Compared to a failed strut top a harsher than normal ride on an old car is not going to set off any alarm bells in the Citroen legal liability department... Funny how the physical design of the hydraulic tank is completely redesigned in the C5 and bears little resemblance to the Xantia design...

Or how about the heater blower problem which ALL S1 Xantia's eventually succumb to ? (My first Xantia had already had the blower hotwired before it was 8 years old) At least they tacitly acknowledged that problem by adding a relay in the S2...

Face it - Citroen's are built to a price, just like most other cars. Some would argue even more so. They have flaws and design mistakes, and there are some things that can be modified to be improved with the benefit of hindsight.

Your suggestion that "looking at theories you can discover problems that don't actually exist" is pretty damn insulting to be honest. The harsh ride came first, then the attempt to track down what was causing it, not the other way around. I didn't come up with a theory and then go looking for a problem... If the car was riding properly in the first place I would never have spent so much time over multiple years trying to track down the cause.

I expended untold amounts of time and money (mostly time) ruling out all the "usual" suspects, as I have documented in great detail in other threads and mentioned a couple of posts ago. Only when the car would not respond to any of these did I start exploring more "out there" explanations for the problem, and only then did I start to get results and start to get some understanding of the underlying cause. I can't even remember whether it was me that first came up with the connection between air bubbles and ride harshness or not, but I certainly took the idea and followed it to its logical conclusion with some proper investigative work. (Did anyone else have a clear loop of return hose fitted on their tank for over a year to monitor the situation and try to prove a correlation between the quantity of air bubbles and the ride quality ? I don't think so...)

I know how a Citroen should ride DickieG, I've owned GS's and CX's, (my first car was a GS, it's kind of hard to forget your first car...) We've had 5 Xantia's in the family (3 of them owned by me personally and driven daily) and I've driven or ridden in a number of others such as David's, Steve's as well as a few back in NZ so I also have a fair idea how they should and can ride.

This problem of intermittent harsh ride despite all attempts to cure it did NOT exist on GS's and CX's, and from what I have heard from BX owners (I've never driven one) it didn't exist there either. This design flaw was introduced in the Xantia and removed in the C5. The design and layout of the hydraulic tank in the Xantia is flawed and I believe that is the root cause of the problem. As soon as the return lines start getting a bit old and perished, allowing excessive quantities of air bubble to be sucked into leaky return joints to return to the tank, instead of harmlessly diffusing to the surface they overwhelm the design and layout of the filters and header unit allowing the pump to suck the air back in.

Please accept the fact that you can't prove a negative, and that by failing to prove the validity of this "fix" on one car, (I would call it a workaround not a fix) you do not disprove that it can work on some cars. Certainly not to the point where you can start making claims that people who have had success with such modifications are simply deluding themselves and looking for problems that don't exist. I wouldn't dream of casting such aspersions based on a sample size of one and neither should you. Absence of proof is not proof of absence.

[DickieG]

Me troll? Do me a favour I have a different opinion so get over it. I don't go looking for problems where they don't exist, you should try this approach as it makes life sooo much easier

[CitroJim]

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