Doseur : that sinking feeling ?

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cauchoiskev
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Doseur : that sinking feeling ?

Post by cauchoiskev » Sun Jun 17, 2007 9:54 am

Back-end drop, particularly under braking, is usually caused by a leaky brake doseur. I had changed mine for a lower-mileage one from the breakers a couple of years ago, which solved the problem for a while, but now it is back. After two hours the back end is on the stops. This is only aesthetically annoying, but as it gets worse, the brakes will eventually fail. I had read several times that the doseur could not be fixed, as the leakage came from worn pistons. There was only one opinion to the contrary, which was from AndersDK on the old CitroenZ forum, who claimed the doseur could normally be refurbished by replacing a few joints, 11 12 and 13 on this diagram :

Image

The rubber end cap 3 can also be replaced.

Having seen the price of a new doseur, I decided to try Anders' method. It took me a while to understand how worn joints could cause a leakage return, but finally this is how I think it happens :

Image

So, off to Citroën to get the bits :

Image

The man at the counter seemed a bit worried : " We never open those things, mate " . Aye, right, it's a lot more interesting to sell new ones ! Good news, though, joints number 12 and 13 are still available and reasonably cheap. The end-cap 3 is also available. Joint 11 however is no longer available, so if your doseur is leaking from there, you'll need to find another source.

And so to work. Here's the doseur, access not too bad in an N/A diesel :

Image

Haynes says to put the front of the car on axle stands. At least on this car and the 14s, this is pointless as the whole job can be done from the top. First, put the car in low position and release the pressure. Then unscrew and pull out the top three hydraulic pipes (this is the more recent 3-piston doseur). The bottom one is a bit of a pig, so disconnect the speedo cable in the engine compartment (red arrow in the photo of the engine bay), and undo the two 11mm nuts behind the brake pedal first to give you a bit of leeway :

Image

Then you can pull the doseur, tilt it and get at the bottom pipes. Start dismantling it at the pedal end. Lever off the ring, pull off the end-cap, then there's a circlip to take out and here are the bits which sould come out :

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At the other end, it's easier to shove the metal plug back a bit to get the circlip out. :

Image

Then out comes this lot, with a bit of poking from the other side :

Image

The teflon and O-rings (one on top of the other) have to be pried out with a little hook :

Image

Don't bother touching the end seal O-ring unless you have a replacement for it.

All in all, you've now got this :

Image

The photo shows the bung plug still in place, you can take it out for washing no problem, as there is no adjustment. So, wash everything in petrol, dry with compressed air, then start putting in the new joints, O-ring first, then the teflon one on top in the same groove. Take care, as it looks fragile and apt to kinking. To get it in, you need to form a " heart " shape, according to the Citroen document here : http://www.rwbsmith.plus.com/citroen2/Brakes/doseur.pdf . The best I managed was this, it worked :

Image

After that, it's proverbial « reverse-order » time, with a lick of LHM on the moving parts .

Here's a close up of the " right way round " for the middle piston in case you have any doubts :

Image

To get the doseur back on the car, put on the bottom pipe and return first, then fix it with the nuts at the brake pedal before putting on the remaining pipes and return (can anybody explain why there are two separate returns which come from the same bore ???). Screw the speedo cable back on again, pressurise the system, start the motor and check for the dreaded external leaks, particularly at the motor-end where the old joint had to be re-used.

VERY IMPORTANT : carefully purge all four brakes before driving. If you have an old two-piston doseur, you have to purge it as well.

After all this I did a quick brake test back and forth, A-OK, before whipping off the brake return at the reservoir. SH!T ! No difference, it was dribbling out exactly as before. Fluorescent green despair !

However, two minutes later I had another look : nothing ! Not even a drop ! RESULT ! It would seem that just after braking there remains some pressure in the return which makes it dribble for a minute or so.

Next morning, the car was still up, in fact the front end was marginally lower than the back.

Conclusion : if you plan on keeping your BX for some time, and feel up to this ( fairly easy ) job even some time in the distant future, buy those joints now. The rubber end-cap is less of an issue, the one on my 300000km doseur still looked new. Joint number 11, which was apparently available in March, can no longer be obtained. It stands to reason that this is going to happen to the other bits sooner rather than later. It's only a couple of quid for the pair of joints, and I am certainly going to get another pair " just in case ". Of course, none of this will work if the pistons themselves are worn, but if the LHM has been kept clean through the life of the car, that's unlikely before very very high mileages.

Hope this can help keep a few more ^^bx> on the road...
Last edited by cauchoiskev on Sun Jun 17, 2007 3:39 pm, edited 1 time in total.

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Post by Stewart (oily!) » Sun Jun 17, 2007 12:20 pm

Nice article, good pictures too.
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Post by Mr B » Sun Jun 17, 2007 2:12 pm

Excellent work. 8)
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Post by Doz » Mon Jun 18, 2007 9:27 am

Can we have it sticky please?
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Post by sleepy0905 » Tue Jul 03, 2007 11:06 pm

done these before they are very easy to do as they dont wear mechanically infact i still have one on the bench but i cannot remember if i overhauled it or not the seal no11 dont worry about as it doesnt do any movement so as long as you are carefull with the dismantling you can reuse the seal with no problems.

Oh yes if anyone wants the valve i have here you can have it and i will bring it to the national.
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!

Post by simonbx17 » Wed Jul 11, 2007 7:29 pm

hi sleepy, just read this article i think my doseur valve is leaking is your valve still availiable?

thanks
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Post by sleepy0905 » Wed Jul 11, 2007 7:36 pm

it is i will pm you with details.
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great

Post by simonbx17 » Wed Jul 11, 2007 7:38 pm

great i will be at the national so pick up not problem. :)
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Post by AndersDK » Sat Oct 06, 2007 6:45 pm

Thanks mate 8)
Thats some nice result from a rough write up I did several years ago -

The seal ref 11 in the exploded view is still available for the later 3 piston doseur valve. Its a 42mm dia ring 1.6mm thickness. It wont fit the earlier type which have a smaller diameter (appearantly ?)
The seal BTW is the same for BX/Xan 1+2/XM 1+2.
Anyways any industrial Viton seal (for mineral oils) approx the same dia/thickness will do the job.

95638813 O-ring seal
approx £2 ex vat
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Post by cauchoiskev » Tue Oct 09, 2007 5:28 pm

Many thanks, Anders, for showing the way...

However, a word of warning to anybody attempting this job : I have bought two o-rings since doing my doseur (part n° 79 03 065 984), and they were both the wrong size :shock: (too small).

These parts come from the factory, so there is a fair chance it could also happen to anybody else, so verify before opening/taking off your doseur.

The correct size is 16.4x19-1.3.

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Post by Kitch » Sun Feb 03, 2008 11:14 pm

My car used to sink very quickly, and coupled to the fact the PAS didn't work the now departed Tom suggested that my doseur could be causing my PAS to fail.
My car now no longer sinks quickly since I found a small leak and fixed it. In fact it stays up for days, but the brakes seem quite dead in feel....most BX's seem like they could put you through the screen, but mine doesn't. Still stops well, just with a bit more effort?

I'm taking the engine out over the next couple of days, and replacing heaps of stuff in a hope to fix all the little niggles. Question is, do I do the doseur? Because in a valver, from what I can see, you have no chance of getting to it with the engine in! I too found that a kit wasn't available, but when trying to find the individual parts I was asked if its two way or three way? Is that based on whether it has ABS or not? Or the build year? (ORGA no says its an early 1990 car).

Its not leaking, but the engine is already half out and I'm on limited time to get this sorted. If there is no possible way it could affect my steering, I'll probably just leave it, but with a brand new rack, pinion and ram I want the steering working. If it doesn't after all this I'll be suicidal! :(

Advice gratefully recieved!!

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Post by cauchoiskev » Mon Feb 04, 2008 7:52 pm

The switch-over to 3-piston doseurs was in 1988, so yours will certainly be a 3-piston job. However, the joints are common to both doseurs.

When you say it is not leaking, do you mean internal or external leaks ? How high is your mileage ? I would say, over 100k and it's not worth it. And if you really have no leaks, don't touch it, they fail progressively so you have a good while before you.

BTW there is a test to check whether an internal leak is from the joints or from the pistons : look at the leakage at normal height, motor running, then drop to bottom height and check again. If it's the joints, the leak will stop or reduce considerably at the lower height.

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Post by Kitch » Mon Feb 04, 2008 8:04 pm

No its not leaking at all. It's done around 100k miles, but after a phone call to the extremely helpful guy at Pleidies (sp?) I've decided to leave it. He basically said he's never seen a doseur cause the PAS to fail, but that it is possible in an extreme case. He also said that if that were the case, I'd be able to watch my back end sink within seconds after switching it off :lol:

He's also said he's not so sure it's the pinion either, so I'll wait and keep fingers crossed. Thanks for help though :)

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Post by TB2 » Mon Jul 21, 2008 10:00 am

I'm not sure yet as I was only able to drive my BX very little since I got it, but I think I'm also experiencing this problem. I just called Citroen Switzerland and asked them for those parts, and this is the reply I got:

95 638 813 - seal 1.60chf
95 495 759 - seal 4.40chf
79 030 659 84 - seal N/A
95 640 067 - cap 15.90chf

On the picture from the initial post, Join 11 (Part number 95 638 813) is missing, but Anders said that it is still available for 3-piston doseur valves (which I think I have because it's a 1989 model). That would mean that I would miss part 79 030 659 84 which is not available here. Which one is that? Because on the picture it is a bigger one - though from joints 11, 12 and 13, number 11 would be the biggest. So I'm rather confused about which part number relates do which part on the diagram. Because if part 79 030 659 84 is vital to this, I won't order the others.

Image

Thanks for your advice!

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Re: Doseur : that sinking feeling ?

Post by AndersDK » Mon Jul 21, 2008 4:00 pm

Image

No 11 is the end cap (large) O-ring seal 95.638.813
no 12 is the tephlone seal 95.495.759 - 14,7X14,9-2
no 13 is the rubber compressor O-ring 79.03.065.984 - 16,4X19-1,3
no 3 is the rubber actuator knob 95.640.067

All parts are vital.
But you may with good luck be able to Re-use the old part no 11. This is the large O-ring that seals the end cup in the valve body.

All part s are still available at your local Citroen dealer, despite my previous comment on this :roll:
Last edited by AndersDK on Fri May 22, 2009 4:47 pm, edited 1 time in total.
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