p osted this topic yesterday but didnt really explain properly. combi boiler has been making a humming whirring sound for ages had some one look at it and said it was a combination of the fan and pump. i asked if it would pack up on me and they said no could just be age and just started making noise. bearing in mind system only 6 years old. anyhow past couple of days when the boiler is not on ie; no heating on, every now and again its making a slight grating noise then a ringing noise which starts quite loud then gradually stops over a period of 10 seconds or so. so my question is could the noise when the boiler of be the fan or pump still, or something else replies appreciated thanx forgot to say the humming whirring sound is only present when t he heating is on