Abs And Brake Delay - CITROEN XM Internet Reference

The brakes

91 ABS and Brake delay.

Hmmm... far be it from me to put my spoke in where others obviously have more experienced spokes,
but I feel the need to add my experiences to the fray:
After work to the hydraulic system on my 24v, I experienced problems with the brakes. In my case, any
pressure on the brake pedal took approx 1.5sec to be transmitted to the brakes. This caused much
distress and near accidents, untill I took the car back and waited while the brakes were bled (from the
actual calipers). They were then fine.
Now, I haven't studied the XM braking system in any great detail but I assume that there is a single
hydraulic line going to the caliper, through which pressure is transmitted to the pads. I assume that if air
somehow manages to get into this part of the line, the only way to remove it would be by bleeding from
the brakes. I am eager to be corrected on this however.
Does this sound reasonable?
Regards
___________________________________________________________
Richard Williamson
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Right on all counts Richard.
Air in the hydraulic lines close to the brake callipers will cause an alarming but usually very brief braking
delay.
The air in the space needs to be compressed before the pads can start to pinch the discs. In a
conventional system 'pumping' the pedal does just this. On our system where we just release pre-
pressurised fluid into the calliper pipes the delay is an obvious result.
Your 'Brake malfunction diagnostic certificate' is in the post.
Harry
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It doesn't just sound reasonable - it is right.
The hydraulics for the suspension and steering will bleed themselves - they have return lines for the air
to come back to the reservoir - but the brakes cannot bleed themselves. They will need manually
bleeding. If the ABS is the problem, though, I can't see it'll help.
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91 ABS and Brake delay.
Citroen XM Internet Reference Version 1.0
3/3/99