I agree with this kid. if it is not tight then that might be the cause of the problem. Also, if the little hose connector bolt is knackered then that might be the cause. If there is an olive at that end of the hose, that might have gone. Or the seal could have broken. To be honest, your best bet is to ring up some sort of bike shop that is pretty big otherwise you might be out of luck. Going back a while now, i had to get a new magura olive and most of the little shops i rang up didnt even know what magura was so choose your shop wisely. I hope this helped