Anti-sink sphere just died ?

[Mandrake]

Hi All,

As I mentioned in another thread we just bled the rear brakes on my Dad's Xantia due to it lifting up at the rear during braking, and sure enough there was air in them.

But what amazed me was the *amount* of air - more than I've ever seen bleeding the rear brakes on any Citroen before. A huge amount from both left and right. From one side the oil collected in a container was still frothing like a beer when it was sitting in the container.

Whats more, 90% of the air was right at the brake end of the lines and came out immediately, whereas normally you'll get a few small bubbles from further up the pipe.

The rear brakes were bled approx 6 months ago, the rear suspension spheres are ok (and less than a year old) the accumulator sphere is ok, and I don't think the pump is sucking in any air either (no bubbling in the tank) so I'm wondering - has the anti-sink sphere finally punctured and dropped its guts

It is of unknown age and is the only sphere not tested or replaced yet, there is a good chance it is the original, on an 11 year old car...

No apparent change in the sinking characterstics either. Any comments on where all the air could have come from ?

Regards,
Simon

[AndersDK]

You did the Citaerobics extensively before bleeding the brakes ?

Any air in the rear brakes system can only originate from the rear suspension - and of course the rear a/s when fitted. Air taken in by the pump can not be exclusively directed to the rear brakes. It would certainly give massive symptoms on front brakes too, i.e. the wellknown delay in the brakes function.

As the brakes lines are dead ends in the system - you can not have air accumulate or build-up - because there is no route the LHM can be expelled by the air. Only the ever so small volume shift over time from pistons moving out a bit more when pads and discs wear down - will allow for LHM (and gas/air) to move out towards the calipers. (symptom of the delayed rear brakes action)

A leaking a/s sphere would therefore mostly expell the gas rearwards into the suspension. (Symptom rear of car shooting up during braking)

I'd say your gas/air problem is a mix of a couple of things. Neglect of bleeding and/or Citaerobics after sphere change and brakes service is a very good candidate. Then of course an 11y old a/s sphere is a notorious suspect.