Sorry that my first post is a problem, Having had this problem: http://www.audi-sport.net/vb/showthread.php?t=63927 And solving it by removing the grommets I've now found its caused a new, more worrying, effect: Water has obviously got into something because on an icey morning the brakes seize on when the pedal is pressed. Normal function returns when the temperature rises The servo activates fine - it just doesnt release properly. I'm wondering if there's a vent or non-return valve that could have been contaminated with water - theres no chance of it getting enough warmth and air circulation to dry out. Once the brakes are defrosted the function is normal. Does anyone have any suggestions on which component will have failed?