What is this noise from the boiler?!

[Sam4]

I have a myson apollo fanfare boiler. There are 2 strange noises that concern me...

1. When the CH and HW is off the boiler seems to come alive every 4 minutes. It is not firing up like when the CH or HW comes on but rumbles away for about 30 seconds and then turns off but then comes on again every 4 minutes. Could this be anything to do with the pump?

2. The latest noise sounds like water dribbling into the HW tank - its very loud and its only just started doing it. Could this be air trapped in the system?

Any advice appreciated! Cheers

 

[gavinda]

on the random firing...sounds like a sticking 2 port valve maybe..and the trickling noise... pump running when the valves are stilll shut and pushing through the bypass.