Doseur Valve

davetd · Post by **davetd** » 29 Dec 2006, 12:50

Morning

Now I've cured one of my cars two annoying traits (the lurchy throttle) I thought I'd approach the other one in a different way.

The car sinks quite soon after the engine is turned off (it's not anti sink, and yes I've changed the accumulator, LHM, filters etc and reseated the non return valve in the regulator). The regulator clicks every 8 seconds.

I've noticed several things that become normal if I apply the brakes...

Holding down the brake pedal hard (I mean standing on it), the regulator starts cycling every 30 secs,

If I turn off the engine, after 30 secs the front suspension starts to creak and slowly drop. If I pump the brake a couple of times and hold it it stops the suspension dropping. On releasing the brake...you've got it...she starts to sink again.

Finally, if I traced the correct return pipe, the one from the brake valve when removed sprayed my garage wall with LHM with the engine idling and pedal released.

Chew that one over chaps

regards

davetd

Post by **Peter.N.** » 29 Dec 2006, 13:04

I think you have answered your own question! My XM looses pressure very quickly after stopping. I rolled it forward about 20 mins after parking it the other day and nearly hit a car on the other side of the road - no brakes, but then its been like this for the last 20k or so, and it still drives OK. I might have a look at it when the weather improves.

AndersDK · Post by **AndersDK** » 29 Dec 2006, 13:19

Have the same problem on my BX TD.
Its the doseur valve return hose that is leaking out badly the pressure.
I have no more than approx 3-5 secs tick interval with a new accumulator.

As I see it, the only solution is to replace the doseur valve. I stock a couple of overhauled units, so whenever I get the time ...

You can use a doseur valve from any Xantia model.

Post by **CitroJim** » 29 Dec 2006, 13:32

Good diagnosis Dave...

For reference mine (non-antisink) stays up for about 20 minutes before it starts to gracefully sink and takes a good 45 minutes to go right to the bumpstops.

The stop lamp goes off after about 5 or so seconds usually.

Strangely mine never "ticks" as such. It has a long hisssss whilst it builds pressure and then about every 20s or so it has a short hiss. Next time I swap the accumulator I'll try reseating the ballvalve to see if it stops hissing. It has been like this for all the time I've had it and does not seem to be a problem. The only problem is that all my family and friends know when I turn up with the hiss and squeakly rear brakes

I've had several goes at the brakes but I can't stop thenm squeaking for any longer than a day or so

davetd · Post by **davetd** » 29 Dec 2006, 15:27

Mine hisses or clicks, depends on her mood

The funny thing is it was always the front that sank first, for nearly a year. A couple of weeks ago it was the back that went first, leaving the front in the air like a BX. Now it seems to go down level

citronut · Post by **citronut** » 29 Dec 2006, 19:27

citrojim wrote:Good diagnosis Dave...

For reference mine (non-antisink) stays up for about 20 minutes before it starts to gracefully sink and takes a good 45 minutes to go right to the bumpstops.

The stop lamp goes off after about 5 or so seconds usually.

Strangely mine never "ticks" as such. It has a long hisssss whilst it builds pressure and then about every 20s or so it has a short hiss. Next time I swap the accumulator I'll try reseating the ballvalve to see if it stops hissing. It has been like this for all the time I've had it and does not seem to be a problem. The only problem is that all my family and friends know when I turn up with the hiss and squeakly rear brakes I've had several goes at the brakes but I can't stop thenm squeaking for any longer than a day or so

Jim
could your squeeking rear brakes be a build up of corrosion between the rear calippers and arms
regards malcolm

davetd · Post by **davetd** » 31 Dec 2006, 10:02

AndersDK wrote:Have the same problem on my BX TD.
Its the doseur valve return hose that is leaking out badly the pressure.
I have no more than approx 3-5 secs tick interval with a new accumulator.

As I see it, the only solution is to replace the doseur valve. I stock a couple of overhauled units, so whenever I get the time ...

You can use a doseur valve from any Xantia model.

Morning

Is this return hose fed by a return valve using a ball bearing?

If so could it be 'knocked about' and maybe corrected by removing the hose and sticking in something pointy?

Just an idea as I've been looking at the procedure for changing the doseur

Also does anyone have an exploded diagram of the doseur, just out of curiosity?

cheers

davetd

AndersDK · Post by **AndersDK** » 31 Dec 2006, 20:59

The doseur valve is a pressure tap for the brakes pressure. Works by 3 sliding precision pistons in a precision bore.
There are no seals involved in the function, and also no ball valve which can be reseated.

It is dramatically different from a standard brakes master cylinder.
Documentation found here :
http://www.rwbsmith.plus.com/citroen2/Brakes/doseur.pdf

(it is for a BX but the Xantia is the same)

Mandrake · Post by **Mandrake** » 31 Dec 2006, 21:53

AndersDK wrote:Documentation found here :
http://www.rwbsmith.plus.com/citroen2/Brakes/doseur.pdf

Broken link ?

Regards,
Simon

jeremy · Post by **jeremy** » 31 Dec 2006, 22:37

You should be able to find it from here:

http://www.rwbsmith.plus.com/citroen2

For some reason Anders link should have a capital 'B' for brakes - which must show he typed it rather than copy it!

davetd · Post by **davetd** » 01 Jan 2007, 12:18

So how is it allowing such a high pressure return on my car then?????

citronut · Post by **citronut** » 01 Jan 2007, 23:18

the rear suspension presure returns via the brake dozer valve
regards malcolm

davetd · Post by **davetd** » 02 Jan 2007, 18:44

When I changed my LHM and Accumulator in the summer the car behaved for about 3 days.

Could a hydroflushing possibly cure it. Is is likely to be something sticking open ?

cheers

davetd

AndersDK · Post by **AndersDK** » 03 Jan 2007, 20:51

Dave -

The doseur valve has been a known issue on most hydraulic Citroens ever produced. What exactly happens I dont know. Mostly it pays removing and overhauling (cleaning) the valve, by dismantling and cleaning all the internals.
There are 3 weak springs which keeps the slider pistons equally spaced.
These springs must be exactly same length, and will mostly gain by being expanded a wee bit by hand.
The rest is pretty much simply cleaning out gunk & debries left by the hydraulic system.
The rear brakes circuit involves 1 rubber & 1 tephlone circular seal. These seals are responsible for the rear sink - on NON anti-sink (standard) models - because of wear and then consequently an internal leak out the return hoses.

Overhauling the valve is a bit more complex than overhauling a standard brakes master cylinder. But certainly worth the effort.
All tech info is found in the pdf document from he webpage I submitted.

For some obscure reasons, it has shown that brand new valves off the shelf seems to leak from the first second in service. A bitter ( & costly !) experience for many owners.

jeremy · Post by **jeremy** » 03 Jan 2007, 22:37

I expect the reason the spares valves leak is something like the wide tolerance ones were sent for spares rather than being fitted to new cars which might result in a warranty claim!

If their poor performance was ever reported it would probably prove too difficult to find out who had made the error!

Strange how the Xantia TD's with the N/A connecting rods all seemed to turn up on an island - Mallorca wasn't it? It was many years in fact before they broke!