Sinking Speed?

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CitroXim
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Sinking Speed?

Post by CitroXim »

OK, I know I don't have a BX but I do have a very early Mk1 X***ia in my fleet which shares a similar, straightforward hydraulic system in that it is a non anti-sink so it sinks like a proper Citroen should.

Now, for a while, it has been sinking really quite quickly after a run and it would sink to its bump-stops after say 20 minutes.

Today I changed its LHM as the old stuff was three years old and rather yellow. I also cleaned the filters although after a Hydraflush three years ago, they were spotless.

Now it stays up far longer. After an hour it was not far off normal ride height.

Can anyone explain?
Last edited by CitroXim on Sat Apr 26, 2008 8:52 pm, edited 1 time in total.
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Tim Leech
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Post by Tim Leech »

I changed the accumulator on my car recently and now mines stays up for hours, before it went down quickly. I would fit a new accumulator or what they cost from GSF. I have a BX but fitted a Xantia/XM type.
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Post by citroen7 »

I think you have answered your own question Jim you have cleaned the filters and changed the lhm This is typical citroen give them a bit of tlc and they behave themselves :D
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Post by jeremy »

Its actually the LHM - I lost loads the other day when the return pipe from the bottom of the doseur broke up. The LHM hadn't been changed for some time but I doubt if very much was really old due to repairs over the years.

Much to my surprise I now have a car that rises very rapidly and takes many hours to sink (as opposed to about 20 minutes.)

I did look at the tank filter which seemed clean - so I left well alone.
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cauchoiskev
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Post by cauchoiskev »

I have also noticed this. New LHM is a cure for many evils.

I read somewhere that with age the molecules of the oil progressively break down into smaller ones, which allows them to leak more easily past the seals.
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kermit the frog
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Post by kermit the frog »

Hi Jeremy

The filter you can see easily is the return filter the pickup filter is behind that one and is round and conical in shape and usually very dirty.
The little metal clip on the large filter hooks into the pickup filter.
The pickup filter is the one that makes the most difference to how fast the system works.

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Post by AndersDK »

Further to this issue :

It is assumed that the brake doseur valve always is the deep sinner responsible for the rear sink. But not always. In fact rarely.

The proof is a test where you collect the leak-off flow from the rear cylinders : unplug the rearmost (car's) plastic hose then insert another one leading to a jar. (the front most plastic hose is just the bellow cavity vent hose with a dead end in the rear subframe tube)

It is quite scaring how much the rear cylinders leaks :shock:
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Post by jeremy »

Kermit - as cleaning the filters wouldn't have made any difference there wouldn't have been much point in doing them. In fact I was fed up with the job as I can assure you that taking a doseur off a turbo-diesel RHD car is no joke and I ended up with the engine supported on a crane so i could get a little more room at the back of it.

2 1/2 days to replace a split non-pressure pipe is daft - probably time to look for a more sensibly built car.
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kermit the frog
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Post by kermit the frog »

Hi Jeramy

Sorry if you thought i was being a bit OTT. :oops:

Just trying to help but if you have had a bad day i can understand
Still now you have done the pipe you probably wont have that to do again so the car is ok.
They may be a bit of an oddly engineered car but that's why we have still got them.
At least they are not loaded up to the eyeballs with electronics and airbags and heavyweight safety features that modern cars have.
We don't need park assist , anti collision radar do we.

WE HAVE BX'S NO PROBLEM! ^^ ^^ ^^bx> beers

Regards Kermit :) :)
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DLM
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Post by DLM »

I can assure you that taking a doseur off a turbo-diesel RHD car is no joke and I ended up with the engine supported on a crane so i could get a little more room at the back of it.
When Tom kindly replaced the doseur on my last car, he got access by removing the bonnet, loosening the top engine mounts, a bit of heave-ho and insertion of a 3" square baulk of timber between the intercooler and the bulkhead. He then tied an 8mm combination ring-spanner to his left wrist instead of his usual Swiss watch, and did the job in an hour or so. I was rather surprised to finish the job before lunch. Having said thatI know it would take me at least three times as long to do it myself.
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Post by jeremy »

Electronics don't ****ing leak!

By and large I like the hydraulics - and I bought it 9 years ago as a mechanical challenge. I never thought I'd still have it now - and yes I got it going correctly many years ago and by and large its been very reliable - the 2 major faults being its inability to exceed 30 MPH on a test drive (throttle pedal broken off) and random hydraulic warning light operation (incorrectly assembled FDV with the ball bearing valve the wrong side of its support plunger)

Its now done 206,000miles and still returns 47 MPG on medium runs and starts first time and doesn't really do anything it shouldn't. Perhaps its time for a change - I'm working on ancient Land Rovers at the moment but they really do wear out although bits are cheap and plentiful both new and second hand.

Nice Lotus Elan (1600 DOHC - 1966-1973) would be nice but I couldn't carry much junk in it like I can with the BX.
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Post by Vanny »

The effect of the new LHM renewing the performance of the suspension system is pretty simple. From its starting point in the bottle the LHM is a polymer chain style structure (think of it like spaghetti albeit it at a molecular level), give it a little give being forced under high pressure through very small holes in the spheres and valves and the chains break up (think like taking scissors to the spaghetti). Before you know it the viscosity increases as the chains are very much smaller, and hence can leak through gaps that perhaps they might not have to begin with.


I had a very long conversation about this with a technical advisor at Total (who knew a lot more about LHM than i will ever want to know) and basically they reckon efficiency is seriously ruined after about 6000miles. Don't think i'll be changing quite that often though!

Also the Total man says that used LHM should be disposed of at the tip with normal waste engine oil. As does the 'Oil Helpline' whose number is on the back of all oil containers. But dont bother trying to explain that to the man at the tip, we will have a fit! I normally mix in some used engine oil to save from grief these days.
Last edited by Vanny on Sun Apr 27, 2008 10:58 pm, edited 1 time in total.
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Post by mat_fenwick »

Vanny wrote:tarting point
What's that then? Sounds like fun anyway...
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Post by jeremy »

Vanny - its a pity you can't run the hydraulics on diesel - and burn it when its done its job. Fresh change every day!

LHM takes as long as 6000 miles to deteriorate? I'm surprised its that long - I'm expecting my car to go back to its old (and adequate but slow) ways any day now!
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Post by Vanny »

must admit that i find it dies off within 2 weeks (so what 2000miles at best), i wonder if the weather doesn't help. I bet you could run it on Diesel, though not for long!
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