Xantia brake cylinder (doseur valve)

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avidfan
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Xantia brake cylinder (doseur valve)

Post by avidfan »

Hello,
I'm new on here and I'm also new to Citroens so please excuse any faux pas I might make!

My friend has a Xantia, it's a '96 'n' reg 1.9 diesel, it has a leak from the brake cylinder type thing from the front where the pipe(s) go into it. Is there a repair kit for them or does the unit need replacing? If it can be repaired is it easy (I'm ok with a hammer lol) and do just the brakes need bleeding or the suspension too?

Thank you for your patience!
citronut
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Post by citronut »

hi and welcome

if you mean a front brake calipper it is easyer to fit a re/con or second hand unit,

and it is just the calipper you disconect which will need bleeding, with suspension presure up just open the bleed kniple and hold the brake pedel down till you get a solid flow of fluid, then shut the kniple off job done

non of the usual pumpping up down up down as with standerd brakes

regards malcolm
avidfan
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Post by avidfan »

citronut wrote:hi and welcome

if you mean a front brake calipper it is easyer to fit a re/con or second hand unit,

and it is just the calipper you disconect which will need bleeding, with suspension presure up just open the bleed kniple and hold the brake pedel down till you get a solid flow of fluid, then shut the kniple off job done

non of the usual pumpping up down up down as with standerd brakes

regards malcolm
Sorry, I should have explained further...it's under the bonnet where you'd normally find a master cylinder on a normal car lol. Iirc, there are 2 rubber pipes going into it and the lhm fluid is leaking from the top one I think.
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VertVega
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Post by VertVega »

You should clean it and spot the leak source which might be a) rubber hose b) brake protector cap c) other
They can be repaired.

Also try to search the FCF with the "magic words" doseur valve :D
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andmcit
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Post by andmcit »

Sounds like the brake doseur valve. If a pipe is leaking it can only really be
the fastener onto it's end isn't tight enough or more likely there is a split in
the pipe which may simply require shortening if near the end. The pressure
isn't as high as the thinner metal pipes but the volume will be so any split
will lose a lot of LHM fluid.

Incidentally, these brake doseur valves are more prone to leak from their
internal seals (o rings) and can be refurbished with a kit or renewed by
sourcing new/secondhand from eBay. Just be careful undoing the high
pressure metal pipes so as not to round or damage the hollow bolt
fasteners. The ensure the pressure is vented from the whole system the
car hight lever needs to be put on low and the engine run for a minute
or two to pump all the LHM fluid back to the main underbonnet reservoir.
Finally, a purge bleed of air and remaining pressure is done by loosening
by 3/4 of a turn of a 12mm nut on the front of the accumulator regulating
sphere that sits on the front of the gearbox with a sphere attached from it:
don't undo this bleed screw more than that as this will be unnecessary and
will lose a small sealing metal marble/ball.

As Malcolm says, cycling through from low suspension height to high and
back to low a few times will push any air through and out of the system
where it will be released from the venting screw mentioned above.

Take a look at Jims detailed sticky for working on hydraulics for the full
run down and safety precautions FIRST though - these cars will kill the
unwary by crushing you when collapsed to low with no pressure in the
system!!

Andrew
citronut
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Post by citronut »

as others have said determin which rubber pipe is split cut it back re/fit, job done no bleeding needed if this is were the leak is from, the rubber pipes are just on the return circuit, but some carry high volume but no presure as such,

if it were the dozer valve (master cylender) protector cap split you will a drivers foot well flooded with citro blood (LHM),

if air was/is present in the brake circuit the only way to remove it is bleed the brakes, the only air you will remove by rewleasing the bleed valve (12mm head) on the regulator (on front of gear box with sphere atatched), is from the suspension circuit not the brakes,

regards malcolm
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Post by CitroJim »

The leaking pipe is a leakage return pipe. All Citroen hydraulics (with the exception of the front struts) purposely leak small amounts of LHM for their own lubrication. This leakage is collected and returned to the reservoir. The kind of rubber used as terminations on the hard plastic leakage return pipes is very prone to splitting, especially where the pipe is stretched over a barb or nipple.

As the cars age, this is becoming more of a common problem and accounts for many causes of LHM leaks; luckily it's easy to put right.

Note that LHM can be very harmful to many types of rubber and will eat it is no time. If you need to replace pipes either use ones certified for LHM (usually made of Viton and having a green stripe) or use fuel hose that is certified for use with unleaded petrol (SAE J30 R6). Using soft plastic pipe is not a good idea as it will go brittle very quickly in the presence of LHM.
Jim

Runner, cyclist, time triallist, duathlete, Citroen AX fan and the CCC Citroenian 'From A to Z' Columnist...
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