air in brake lines. It can sometimes be very difficult to get it out - if you are going to DIY I would get a 1 man bleeding kit from halfords or auto shop it is just a bottle with a tube and 1 way valve but is indespensable. Keep topping up brake fluid resevoir while pumping brake SLOWLY esp when lifting foot back up to avoid drawing air back in. do it until you have used a whole container of new brake fluid,then close that valve and check pedal,if spongy move onto next brake until brake is firm,u will use a few bottles of fluid but there is no other way (u can prob re-use the fluid in the bleed kit if its clean) leave a message if that works
david
May 2011