Doseur valve

A

ajpolden

Member
Fellow Frogger
Joined
Apr 19, 2004
Messages
295
Location
Launceston, Tasmania
Hi Guys
I have had an ongoing problem with the rear end of my car sinking quickly, also accompanied by a very frequent tick rate from the hydraulic pressure regulator. I found that the brake valve is returning fluid to the reservoir like it's going out of fashion. I hear this a common fault, rectified with a replacement brake controld valve, aka doseur. Is the ebay item in the following link one such part? The item description calls it something else.
http://cgi.ebay.com.au/ws/eBayISAPI.dll?ViewItem&item=4565543389&fromMakeTrack=true
I heard they can be repaired with new seals but it would yield a more permanent fix if the whole part was replaced.
Thanks :cheers:
Andrew.
 
Nah,

that looks like a pressure distribution block. They have called it a 'safety brake valve' as it will allow the brake circuit to always have priority.

seeya,
Shane L.
 
I'm with Shane, I don't think this is what you need.

The bit your after I think is the part that bolts to the firewall behind the brake pedal.
Might pay to confirm that on Andyspares site as they seem to have a bit of a fettish for swapping them over there.


Alan S
 
Brake valve problems

Shane and Alan are both right. I've had exactly the same problem on a GS and fixed it myself.

As far as I'm aware the brake distribution systems on a GS and BX work along the same principle, feel free to correct me if I'm wrong. I'd presume BXs probably have a separate brake accumulator (unlike most but not all GSs) but nothwithstanding. As I understand it the brake control valve (that's the one on the firewall, NOT the priority valve on EBAY) when open feeds front brakes at pressure up to main (or brake?) accumulator max, and feeds the rears at up to max rear suspension pressure. Therefore a supply pipe must interconnect the brake control valve with the rear suspension, to supply this pressure to the rear brakes. If the control valve develops significant internal (or external) leakage, this enables pressure to bleed off the rear suspension, making the car sink fast.

I worked this out on a GS that started dragging its arse shortly after parking it. I knew the accumulator and pump were good and changing both rear suspension cylinders made no difference, and there were no external fluid leaks elsewhere. Put a new control valve in, problem solved.

This is one of the few hydraulic faults that can be diagnosed easily without any special pressure gauges etc etc. Simply disconnect the brake return pipe to the reservoir and plumb a short length of clear hose to it, holding this vertical. Start the car up and get an assistant to operate the brakes. If the brake control valve is in good condition, the level of LHM in the clear tube should remain constant, or creep up very slowly. If LHM splashes all over your boots as soon as the brakes are activated, you've got a defective control valve... Take the filler cap off the reservoir before you try this test!

Incidentally, the valve on my GS was so stuffed that even without pushing the brake pedal there was considerable internal leakage.

I wouldn't be surprised if BX and GS control valves are the same Andrew. Does anybody know? If so, I've sent you as PM as I probably have a spare for you...

Cheers,
Brett
 
Yep that's the one. The bulb at the end of it is the brake valve the brake pedal presses against.

It might still pay to check if will fit your car before you bid ....

seeya,
Shane L.
 
From GSFs online shop, it appears there may be only one for the BX.

N43478 BRAKE DOSEUR VALVE BX BRAKE DOSEUR VALVE UK pounds 85.00


Alan S
 
That why i reckon it would suit. It looks shinier and newer than the one fitted to my car (obviously), the "bulb" at the is different, mine is cylindrical, although that probably means nothing. The mounting looks the same, but without closer and larger images it is hard to tell if the fittings would be the same.
I'll still wait to see how our arrangements pan out Brett.
Andrew.
 
It's different to a GS one too, so no go there Andrew, but any GS owner that needs one I can help out. :)
Brett
 
I have attached an image of the part on my car. As far as I can see it has four rigid lines, a return line, and a bleed nipple, all of which are on the ebay part as far as I can make out. There seems to be another but I don't have my Haynes manual with me to compare the hydraulic circuit with, can anybody check this? IIRC the Haynes book has some detailed information on this part.
Thanks :cheers:
Andrew.
 

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That is the correct part number for a BX - just checked the pr-net site and it has that number plus an exploded view of it and complete parts list.
 

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ozziediver said:
That is the correct part number for a BX - just checked the pr-net site and it has that number plus an exploded view of it and complete parts list.
Click to expand...


I had a similar problem with my CX....but it was the front end suddenly dropping down to suspension bottom. It could do this while traveling down the street, or down the driveway. :(
In my case it was the 'Safety valve'...this is the small hydraulic component near the rear or the passenger side firewall, close to the gearbox.
It's almost inaccessible, in true Citroen style. :joker:
It has a wire that goes to the pressure warning light on the dashboard. That's the one that blinks a few times then goes out once the engine is running, and the system is up to pressure.
Replacing the unit was not easy, but it certainly fixed the suspension trouble. :D :D
Cheers...George 1/8th. :cheers: :cool:
 
I've just given it more thought. I noticed that holding my foot on the brake with the engine off stops the car from sinking at the rear. Once I release the brake, that car sinks very quickly. If the pressure in the rear suspension curcuit is being used to power the rear brakes, wouldn't the rear lower when and while the brakes are applied, rather than after? Or does the brake valve stop this somehow?
Any more thoughts people?
:cheers:
 
Holding your foot on the brake will always stop the back from dopping... In order to drop the wheel must be able to turn ... If the brakes are on the wheel can't turn so the back can't drop. If the back is slightly high after braking harshly the back can drop the the bumpstops when you release the pedal. This is because the height corrector has bleed all the pressure away from the rear suspension in order to try and lower the car and make it level (only the brakes are holding it up).

seeya,
Shane L.
 
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