Doseur valve rebuild

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Oscar
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Doseur valve rebuild

Post by Oscar »

Hi

I realise that I need to do the doseur valve rebuild. Does anyone have a spare that I could have so that the car isn't off the road for too long?

The write-up is awesome by the way, Cauchoiskev

Oscar
(Red BX 1.7TZD ("Well, it is a style icon" - Tom Sheppard)) "Was", Tom, "was"

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cauchoiskev
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Post by cauchoiskev »

Thanks Oscar,

But I'm afraid I made the mistake of forgetting that not all cars are LHD... so I'm afraid you are going to have to do the job from underneath.

As it happens, I have a spare doseur (3-piston). It has 300000km, although inside it looks as new as the one I had with 100000km. Sending from France is likely to be a bit expensive, but if no other UK based possibilities present themselves, it's yours for the price of the postage.

Kevin

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Post by tom »

I'd buy a new one. It isn't cheap and it isn't accessible but it is the very heart of your braking system.

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Jaba
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Post by Jaba »

Hi Oscar

I have just fitted a new one to my Hurricane so have a redundant spare.
You are welcome to it. It was working normally before replacement.
The Joy of BX with just one Citroën BX to my name now. Will I sing Bye Bye to my GTI or will it be Till death us do part.

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cauchoiskev
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Post by cauchoiskev »

tom wrote:I'd buy a new one. It isn't cheap.
Currently 246.46 Euro in France, c.f. a couple of quid for the joints. You pays your money...

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DLM
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Post by DLM »

Is yours early enough to have the pre-changover type of doseur, Oscar? I seem to remember the changeover date was 88/89. I do have an untried old-type doseur stripped from a 19RD a few years back if that's of any use. ON a TZD you don't have to attack from below, but I guess Tom may have advised how to make the working-space from above.

While you can fit the new-type doseur, my impression is that the newer type wear more quickly than the older type (though whether this is seal wear or metal-to-metal wear I wouldn't like to say). I've had more doseur-wear problems on recent BXs than older ones, through 2 pre-88s and about 6 post-88 cars, which I appreciate isn't a perfect statistical sample....
Occasionally constrained by geography. When not driving, can rely on ferry, two wheels and musclepower when a couple of miles as the crow flies would become a round-road-trip ten times the distance.

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AndersDK
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Post by AndersDK »

I've just had 3 doseurs rebuild : 1 of the early 2 piston type and 2 of the later 3 piston types.
I could not recognise any mechanical/bore/piston wear what so ever.
But despite one doseur came off a car which had been running approx 2400km with hydraflush, all 3 were scaringly mucky inside :shock:

It was closer to MUD than MUCK - even the hydraflush one :roll:

This is well and truly exactly as I remembered it approx 7years ago when I last did a couple of doseurs.

The only thing that seems to help is to replace the pressure rubber O-ring - which presses the tephlon ring seal against the rearmost piston - in the rear brakes circuit of the doseur valve.
You will damage the tephlone ring when you remove it, so it must be replaced as well, but I've not yet seen a worn out tephlone ring in the doseur valve. Its always because of too little pressure from the rubber O-ring, as it is pressed flat over its service life.

Its very important to press in some LHM in the doseur innards before refitting (bicycle pump or test setup). Also remember to bleed the brakes well after a doseur valve replacing. Any airlocks in the piston circuits will make the doseur leak like it is shot internally.
C U / Anders - '90red16riBreak - '91GrisDolment16meteor - Project'88red19trsBreak
dead cars : '89white 16RS - '89antrasitTRDturboEst - '90white19triBreak

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cauchoiskev
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Post by cauchoiskev »

AndersDK wrote: I've not yet seen a worn out tephlone ring in the doseur valve. Its always because of too little pressure from the rubber O-ring, as it is pressed flat over its service life.
I would agree with this. I did a 130000km 1990 one and a 300000km 1991 one and they both looked exactly the same on the inside. They were also leaking about the same amount of LHM.

In other words, doseur failure is time-related rather than mileage-related, and all existing BX doseurs have already reached or passed their serviceable lifetime.

Buy your joints now !