Xantia S1 rear brake fluid pressure

[bernie]

Hi all, long time since I posted.
Need your help again.
My brother's Xantia TD S1 1996. Rear brakes, both sides, absolutely no pressure when pedal is pushed.
Have not investigated the other than suspension works ok.
I believe the pressure comes from the so called anti sink (centre) sphere.
If the sphere has failed completely would this cause the rear brake failure?

Thanks
Regards
Bernie

[Deanxm]

The anti sink sphere holds a reserve of pressure for emergency braking when the car is not running only, do bear in mind that the rear brakes are fed from rear suspension fluid, if there is no weight in the boot then the brakes wont do a thing, when testing the rears you need to raise the car to full height via the lever in the cabin to raise the pressure in the rear suspension to give a good supply to the brakes, either that or get three people on the back seat

D

[Mandrake]

Hi Bernie, long time no see

When you say no pressure, can we assume that you're trying to bleed the brakes and nothing is coming out ?

If so how is the car supported when you're doing the bleeding ? If there isn't enough weight on the rear suspension when bleeding nothing will happen... I had a similar problem just the other day where even though I had the manual height lever right up and one rear wheel still on the ground I couldn't get any pressure at first.

I had a jack under the subframe on the side with the wheel off and had to lower it down quite low to put most of the weight on the opposite wheel before I could bleed them. This is usually a sign that the manual override linkage is out of adjustment and isn't fully overriding in the maximum height direction.

[bernie]

Ah Simon hello my friend, thought you were in Aussie land.

How are you?

I'm not bleeding at all. His Xantia has just failed the MOT on 'lack of fluid pressure on rear brakes'.
I had a quick look, both disc shiny clean with obvious pad contact indicating they have worked recently.
I jacked it up via the tow bar, with car running brakes applied, rear wheels spin easy.
As I said it's a long time since I worked on a Xantia so cannot remember it's foilbles.
I take it they will spin unless the rear suspension is loaded.
Does this point to the h/c being incorrectly adjusted or the mot tester incorrectly testing as the rear brake look like they work ie shiny

Bernie

[Deanxm]

Sound like the mot tester doesnt know citroens, i would just book it back in with some weight in the boot and all will be well.

D

[bernie]

Thanks D

[Xaccers]

Look down on the callipers from above, ensure they are parallel with the discs.
Corrosion builds up between the arms and the calliper pushing it out at an angle, eventually it can get so bad the pistons can't apply enough pressure on the disc.
If that's the case you need to carefully remove the callipers trying not to sheer their bolts, and then chip off the limescale like stuff.
You then may need new pads and discs depending on the wear.

If you need weight in the boot for the rear brakes to work well enough, then there is something wrong.