Popping noise

[Roger Lock]

I have a Grant Vortex Pro 26/46 Boiler serial number 669556060722786 Reilo Burner Burner Model Rdb2.2. It was installed just over 2 years ago. About 6 months ago I noticed a 'popping' noise when the boiler started up and/or cut in as a result of being called upon by the thermostats. The noise has become louder and louder. Unfortunately when it became too noisy and I contacted Grant they told me the warranty had run out. I have had 4 people try to sort out the problem including the installer and the chap who commisioned it but they are unable to solve the problem. Has anyone else experienced a similar problem and if so what if anything have you done about it. The system was completely drained when the boiler was installed and clean water runs through the system

 

[Exedon]

First if your boiler was installed/commissioned by a Grant registered installer and was serviced at correct intervals the vortex pro has a 10 year warranty .
What flue system is on your boiler? clear pictures would be useful.