Ongoing air probs

[jelboy]

I have an air issue with a system that I think I have cured but now have another prob..
I have a Worceser 28 Greenstar which has been installed 3 years. I have converted it to a sealed system recently which has cured 99% of all probs except when in heating mode only there is a constant rumble.. The pump is a fairly new 15/60 so I do think that is it.. Or could a pump go bad after a year?
Any clues would be helpful
Thx
Jelboy

 

[megawatt]

When you converted it to a sealed system did you install a bypass?

 

[jelboy]

Yes to by pass and it is a y plan system so the 3 way never closes anyway.. and all the downstairs rads don't have trv's so plenty of by passing available...!
Any more ideas, please?