Hi...You have probably solved this problem by now but I'll give an answer which will hopefully help others.
On both of the front calipers, the pistons need to be rotated upwards towards the top of the car, whilst applying compressing pressure at the same time. This translates to a left-hand thread for the o/s caliper and a right- hand thread for the n/s caliper. Don't forget to loosen the reservoir cap as you will be forcing fluid back through the system. If excessive pressure is required, I would be tempted to loosen the bleed nipple to relieve pressure because forcing fluid (and possible associated gunk) back through the ABS pump could be a bad idea. This may result in you having to bleed the system however.
If all goes well this is a simple procedure. Just remember the pistons go back by turning anti-clockwise on the drivers side, clockwise on the passenger side.
You can buy a special tool which will probably cost about £20 or you can try to use a screwdriver or similar. Let me tell you that the tools are worth buying - but check the thread.
Good luck
citroenadmirer, March 2010
