10 minute Xantia mod....what a difference!

[cc101]

Hi all, as promised I've taken a few videos, I'll just post one now and another tomorrow or monday.

Mandrake the car car feels fine on the motorway.

In the video I put everything back as it should, I fitted a bit of pipe to the main return so it is the same lenght before I cut it.

The bubbles don't look that big on the video but they are!


http://static.photobucket.com/player.sw ... d21c0b.mp4" onclick="window.open(this.href);return false;

[Mandrake]

Just got a chance to watch your video - I normally read the forum on an iPad which can't play your video and kept forgetting to check it on a laptop...

Was that video taken before the modification ? (EDIT: just noticed you said you re-instated a pipe to emulate the section you cut off for the purposes of the video) I can clearly see the bubbles on the video and that's about equal to or perhaps worse than the quantity of bubbles I was seeing in my clear loop in the return line going into the tank when testing my previous Xantia which had a lot of trouble with intermittent crashy ride...(the one where I fitted the U pipe)

Here's the diagnostic loop I had in the return line: (and also the mystery o-ring)





The interesting thing is that if you get a lot of bubbles going into the tank via the return line (or due to frothing in the tank) they keep recirculating to the pump and back again as when the pressure regulator is in cut-out mode (which is most of the time) there is a loop between pump, pressure regulator and back to the tank, so once a large quantity of bubbles get in they go around and around in circles... Also the power steering forms a similar loop with continuous flow.

Preventing the bubbles from being drawn into the pump inlet eventually cuts down the rate at which bubbles return to the tank via the return circuit as a lot of the bubbles you see are the same bubbles going around in a loop with a few new extra bubbles each time around. The longer it runs in cut-out mode the more bubbles build up in this loop of oil going between tank, pump, pressure regulator and back to tank, then when the pressure regulator cuts-in to supply the suspension (for example to lift the rear suspension in response to acceleration related squat) this heavily aerated oil is then drawn into the main high pressure circuit where it finds its way into the suspension and brakes...

[Mandrake]

Waiting with anticipation for the rest of the photos

I'm quite keen to perform this modification this weekend as it looks very straight forward and I have plenty of hose clamps of every size to replace the original factory crimp style clamps on the pipes on the tank...

[cc101]

Pictures have not come out that well. A brief run down on what I did: 1. Cut main regulator return pipe to about an inch, angled cut. 2. Removed both plastic return pipes inside D shaped filter. 3. Put filter back on.

I decided to double bank the O-Ring on top of the filter housing aswell (mysterious O-Ring).

Ride still good!

Chris.

[Mandrake]

Thanks Chris. So no deterioration in ride quality at all ? As I'm sure you know most fixes like citrorobics or lubricating the front struts often don't last long before the ride starts getting crashy again, days or weeks, sometimes even hours!

Its been my opinion for a long time that whilst the occasional (maybe once yearly) lubrication of the front struts is beneficial, and is necessary if the front suspension creaks or jumps, that the rest of the improvement in ride is simply the temporary bleeding of air bubbles that is inevitable when lifting the suspension right up then down again while lubricating the struts...

If the weather is good tomorrow and I finish my other job on the car (testing and replacing earth terminals for the engine ECU) then I'm going to attempt the modification on mine Only trouble is I can't find my box of jubilee clips so it looks like another trip to halfords will be needed as all the hose clips on my tank are the original crimp types that I don't have a refitting tool for...

I'll try to take some before and after photos of the modification on my car for the benefit of anyone else thinking of trying it.

[Mandrake]

Sorry Mike, I got another job done on the car today but ran out of time to do the tank modification as well, dismal weather forcast and other commitments tomorrow mean I probably won't get a chance until next weekend. I did go and pick up a set of suitable hose clips for all the pipes on the top of the tank though, so I have everything I need.

[xantos]

I have done the modification and must say that the car is much more softer, even though the electrovalves are not working properly.
Before that the car was stiff even with the electrovalves functioning.

Also cleaned the LHM filters and height regulators.

[cc101]

Great stuff, good to hear that such a simple mod can make a difference!

Chris.

[taffy]

I cant wait to do this!

[Dommo]

Hi Chris,

Very interesting! Give it time though, in my experience this sort of intermittent harsh ride often returns after a period of time...let us know in a week or two whether the ride is still crash free.

I assume you were reading threads like this one ?

http://www.frenchcarforum.co.uk/forum/v ... =3&t=20909" onclick="window.open(this.href);return false;

Somewhere around 6 years ago I posted pictures of my own bodge for this problem on my previous Xantia, I thought it was in the above thread but couldn't find it so it must have been in another thread. As you know the original pipe that you cut has a slot that travels all the way down the side, rather than cutting mine short I clamped a pipe over it that captured the flow and redirected it to the surface as follows:





The idea was for the incoming oil containing unwanted bubbles to be dispersed at the surface of the oil where they could de-aerate easily rather than directing the air bubbles forcibly down into the bottom of the tank right next to the pump inlet.

Yes there are two filters between the return and the pump and the bubbles should travel (slowly!) to the surface, but it seems that if there is sufficient quantity of bubbles coming back in the return line the oil surface tension at the filter is overwhelmed allowing some air to pass through the filters and get sucked into the pump inlet line.

My bodge was relatively successful, the very intermittent harsh ride of that car mostly but not completely went away, and consistently remained improved for years afterwards, the change was big enough that I left it in the car right up until it was sold - the new owner will get a surprise when they go to change the LHM!

If your simpler mod of simply cutting the return pipe short works just as well or better I'm tempted to do it on my current Xantia... please keep us informed of how long lasting the improvement is.

Do you have the measurement of how long you cut the pipe ? And did you deliberately cut it on an angle ? I wonder what the optimal length is, given the average surface level of the oil at normal ride height... is yours above the surface of the oil or just below it ?

PS one other thought, by taking the top of the tank right off and putting it back you might have also inadvertently fixed an air leak on either the pump pickup or main return pipes where they attach at the top...

Mandrake, does this bodge work as well as I'd imagine it does? Might have to find something that will do the job, would garden hose work or is it affected by mineral oil? Any other suggestions?

[Xaccers]

Garden hose is affected by LHM, it goes hard.
Silicone on the other hand is fine

[Mandrake]

Mandrake, does this bodge work as well as I'd imagine it does? Might have to find something that will do the job, would garden hose work or is it affected by mineral oil? Any other suggestions?

I doubt whether garden hose is mineral oil safe, I used a corrugated plastic tube, and I don't remember what it came off. Garden hose is a lot smaller diameter than the stem in the tank anyway.

Yes it did work and made quite an improvement, however I never intended the U tube to be a permanent fix, just a quick bodge to act as a proof of concept.

My original idea ironically was to cut the tube short, more or less identical to what Chris has done, however at the time I had not convinced myself that redirecting the flow away from the bottom of the tank would necessarily solve the problem, (nobody else on the forum had tried it before me as far as I know) so I wanted something that was easy to revert to original, hence the idea of attaching a redirection tube instead of cutting the original tube short in case things didn't work out.

It worked well enough that I just left it in place and never got around to trying cutting it short like Chris's mod. To be honest I think cutting the existing pipe short is probably just as good, possibly even better than the U tube approach, and a lot easier and neater as its 2 minutes work with a hacksaw! (It was a real squeeze getting that extra pipe inside the filter) We also have positive feedback from more than one person as to the effectiveness of this simpler approach.

If you can wait another week I'm hopefully going to get the time to do Chris's mod this weekend then I can report back on how the results compare to my U-tube. (bearing in mind the U-tube was on a different car, and every car is a bit different in its suspension characteristics...)

[Mandrake]

An interesting thing happened today.

I haven't done the mod yet, but the car has not been driven since Saturday so has been parked (facing downhill) without even starting the engine for 4 days, and the suspension had gone down quite a bit - not to the bump stops by any means but it was looking quite low.

I went for a drive and much to my surprise the ride was exceptionally smooth and totally crash free! Although the ride quality does vary a bit normally from day to day I can't remember the last time it was crash free, if ever...

The roads from where we're staying out to the main road are riddled with broken surfaces and potholes and normally it bangs and crashes its way over that admittedly very poor surface. You feel a harsh vibration from the front wing areas when the front wheels hit the broken surfaces or drop into a pothole.

Today there was no harsh vibration from the front wing areas, no crashiness in fact even when going across very broken surfaces I could hardly feel them, the only noise was a gentle "pitter patter" noise from the tyres themselves, no noise at all from the suspension or body and just an unbelievably good ride.

What's more this amazingly good ride continued for at least 10 miles before it gradually started to get a little bit crashy again.

Before anyone jumps out and says "aha, its your Hydractive system working in soft mode properly when it was sticking in hard mode before" nope, its not that - because I put the car in sport mode as well, and the ride in sport mode over broken surfaces was also crash free, and in fact it was better over broken surfaces in sport mode than it normally is in normal/comfort mode. So it's not a hard/soft mode issue.

The fact that the ride was incredibly good and crash free today tells me that there is nothing mechanical wrong with the suspension and that its highly likely that it is air bubbles, as an unexpectedly good ride after being laid up for a few days (which helps bleed the suspension) that then deteriorates again after driving a while is text book symptoms of air bubble ingress.

It makes me even more eager to get the modification done if it will result in a ride this good all the time - it really was amazingly good!

[Mandrake]

As anticipated, the ride has become somewhat crashy again just one day after it mysteriously went smooth and crash free...

I plan to do the modification tomorrow so I'll report back on whether its successful and take a few pictures.

[Mandrake]

Well I've done the modification and taken loads of pictures and will post those along with a write up in a few days however I haven't been able to evaluate the results yet as in the process of doing the job the joiner pipe from the tank to the pump split in half and I've only got a temporary repair with a piece of garden hose in place:

http://www.frenchcarforum.co.uk/forum/v ... =3&t=45169" onclick="window.open(this.href);return false;

I couldn't tell what was going on at first as the system wasn't even able to pump up to enough pressure to put the STOP light out, yet the pump was primed and oil was circulating back to the tank and the pump was ticking as it normally does under load, but it just kept on ticking and ticking and the regulator never reached cut out...the tank was a frothy mess so I knew there must be an air leak somewhere, and finally found a split underneath the pipe when I removed it.

The ride is certainly different but it felt a bit like the hard/soft mode wasn't switching properly, sticking in hard mode at least at the front. In the process of trying to lift the car up (very slowly!) before I found the problem I must have pumped truck loads of air into the suspension, I did Citreorobics a few times and it was still bubbling back to the tank each time the car went down like the froth on a pint

So I'll withhold judgement until I get this pipe replaced and thoroughly bleed the system...