Just done this on my 02 Mondeo. Check the centre of the piston, there should be a hexagonal socket. Use a hex bit on your ratchet, quicker & easier than pliers. No need for 'special tools'. Just make sure you wind it the right way, if the piston pops out it's a pain to get it back in. Had to take the piston assembly off & put it in a vice to get the pressure to wind it back in, then reconnect & bleed the brakes.
Wayne, November 2007
