Brake Doseur Valve Replacement

blueboy2001 · Unread post by **blueboy2001** » 26 Feb 2003, 14:46

Having been quoted silly money to get this changed by a Citroen specialist, I am going to get one of the mechanics at work to do it. He's looked at it and said he'll do it, he's read through the procedure in the Haynes book and pointed out that nowhere does it mention depressuring the hydraulics for the procedure. I too thought this a bit odd, I'd imagine even with the engine off theres a fair bit of pressure in the brakes.
So, is it advised to depressurise the hydraulics to replace the valve? If so, is this done by dropping the car, loosening but not removing the screw on the regulator, then pumping the brakes a bit?
Is the valve connected directly to the brake pedal? Haynes doesn't mention this either.

alexx · Unread post by **alexx** » 26 Feb 2003, 15:44

You must lower the car to the lowest position, to depressurize rear suspension (it's pressure supply for rear brake circuit), and depressurize the system at the regulator, loosening the screw by about 1 turn. I think pumping the brakes several times after that is not necessary, but it wouldn't do any harm.
On BX, brake pedal directly acts to rubber cap on the dosieur valve. On Xantia, I think that a spring is in between.

Dave Burns · Unread post by **Dave Burns** » 27 Feb 2003, 00:21

As Alexx says the suspension must be lowered and the accumulator de-pressurised, whatever hydraulic pressure is in it is also available at the brake valve.
There is no permenant connection between the valve and the pedal.
Get some penetrating oil around the unions ASAP, may save some cursing.
Dave

blueboy2001 · Unread post by **blueboy2001** » 27 Feb 2003, 03:56

I thought as much - having spent the last few weeks reading various guides etc on hydraulic systems, it struck me as very odd that the Haynes manual makes mention of depressuring before tackling the job. The standard of Haynes books has dropped in the last 15 yrs IMO, I've got Mini ones from way back and they are far more detailed and explanatory than the current ones, with better photographs and diagrams even for very simple jobs.
The job is being done Tuesday, so I'll get it in the workshop tomorrow and get it oiled up!
Thanks for the advice.