DS Ups & Downs

[pottsy]

I wondered at the time whether it might be a factory mod to slow the flow, but the flow was not happening at all in this pipe. Presumably it had in the past, but maybe all my fiddling dislodged it enough to block the flow completely.

I've obtained enough pipe and fittings to repair this one now, and I plan to leave the wire out on the basis that I don't reckon it really should be there.

All the linkages seem to be doing exactly what they should do, and the HC was checking out fine. I did as you suggested in that I disconnected the HC from the linkage and operated it manually. It would pump the struts up fine, but not release the pressure to let them come down again. (Note that I had lumps of wood under the jacking points ready to catch the beast should rapid dropping occur. I value my squashy appendages!)

This test first led me to suspect the pipe was blocked, and gradually undoing the pipe fitting at the HC proved it to me as the pressure was able to be drained from there into a bucket.

If the rain eases up enough I'll be able to prove things one way or another today.

Incidentally, has anyone had success with reclaiming LHM that's been drained this way? The container I drained it into was clean, but the fluid probably picked up a bit of dirt off the chassis on the way into the bucket. I reckon if I filter it through (say) coffee filter paper or maybe paper towel then it should be good. (Leaving the last centimetre or so in the bucket with all the larger lumps) Maybe not good enough for the purists, but this stuff is too expensive to just throw away without having a go I reckon.

Thanks for the responses so far, I really appreciate the input to the cogitative processes.

 

[UFO]

I cautiously say that you should be able to recover the LHM using this method. Ensure there is no water in it too.

Not an ideal solution, but I bet you wouldn't be the first or last to do it.

 

[Puppeteer]

Pottsy,
Do not replace the pipe with the wire in it!!
It is there to provide a hydraulic anti roll bar. If you can get hold of a copy of J P Chassin's book 'Why Citroen', on page 39 there is a lucid discussion of the role of that wire. It says, in part "Citroen has jammed a calibrated wire in that pipe. It keeps the vehicle from tilting faster than 4/10th of a second. Should you remove the wire, the rate will become 1/10th of a second and the car will flip over, should you attempt the old trick of making a U turn at 60mph on four lanes."
The hydraulic anti sway bar is of course in addition to the mechanical one.
I would add that I did try to scan the relevant page, but obviously unsuccessfully.
It is a bold person indeed who would try to improve on the original Lefebvre design for DS/ID hydraulics!
Hope this helps explain it.
Cheers
Richard

 

[chris]

Hang on,

Are you guys all talking about the same pipe? Because the return line off the height corrector has nothing to do with roll stiffness, in fact the height corrector shouldn't even be doing anything on corners

The high-pressure side of that circuit, between height corrector and spheres, might have some cross-flow, but that's not what Pottsy is talking about, I think :doh:, and that will all be steel lines whereas the return lines are rubber...

Chris

 

[pottsy]

As I mentioned earlier, I had a suspicion that it might be a factory item. On judicious re-thinking I had assumed that, if it was factory, it was to slow the response under heavy acceleration, ie, nose lifts up high, HC compensates for too high state, nose drops and comes down on lowered front suspension, bump stops come into play, HC adds pressure to compensate for too low state, life returns to normal after heart returns to normal position.

I hadn't thought of it in the context of hard cornering, but it makes sense, like most things that Citroen do.

I will avoid violent cornering manoeuvres until I can replace the assembly with another one.

Knowing all that, however, still doesn't explain why or how the damn thing got blocked in the first place. I couldn't suck or blow air through it at all, even with 100psi of compressor! I can only assume that playing with the spheres, which were higher pressure than nominal DS ones may have forced the wire further up and against the end hole.

Chris. The hose we're talking about is a steel one, and yes, it's the return pipe to the tank. I imagine that the limiting of return has a very similar effect to a mechanical link in that it slows down the "down" response of the HC. In fact the holding of the pressure in the front circuit as a result of this blockage was an extreme case of what this is designed to do in fact!

Hindsight is such clear vision!

The flexible plastic pipe is the "drain", also to the tank, for any internal leakage that takes place inside the HC.

Despite all this, I am still in love with hydro-pneumatic!

Damn clever those Froggie chaps, what?

 

[chris]

Despite all this, I am still in love with hydro-pneumatic!

Damn clever those Froggie chaps, what?

Indeed. From fiddling with the GS I had assumed the height corrector itself had a bit of resistance built in to avoid the kangaroo problem you refered to, but I guess the D is both heavier and more floaty.

You must have been getting a bit desperate, to be drilling holes in steel hoses! :roflmao: :roflmao:

Chris L

 

[pottsy]

Chris

Not desparate, just bemused at the time. The sequence of events was: (1) decide that there was a blockage in the return path. (2) determine that it was in the pipe by undoing the union into the HC and observing the pressure being released. (3) removing the pipe and trying to blow and/or suck through it, unsuccessfully. (4) Poke a bit of wire in and find it came up against an obstruction, so (5) try to remove the ostruction with a small drill.

Once I got to 5 was when things went a bit awry. Murphy's law determined that the drill I used was in fact very sharp, and it slewed sideways and came out the side of the pipe! It was at this stage that I cut the pipe, knowing I had to braze a new bit on anyway, and discovered the wire in both halves.

Note that this is a low pressure return pipe, so that brazing should, in my opinion, be plenty strong enough for the job.

I plan to replace the whole assembly with another very soon. In the meantime I'm enjoying a DS that doesn't behave as though the front circuit was full of viagra!

If I have done it right, the photos below should show the wire after removal, and the repaired assembly.