I have had several problems with my cistern which is only 2 years old - each time I have had to call on DynoRod to fix them. However I now I have a new problem. About 10 mins after flushing the cistern starts making a noise like the rummble of a motorbike starting up (don't laugh) the silver flexible hose attached to the cistern vibrates, I then have to slightly depress the button to release a little bit of water wich makes a gurgling noise and then the rumble stops. Next time it is flushed again the same noise after 10 mins. Any ideas?