How do i stop my boiler being noisy?

I have Baxi solo 50RS boiler which I have had trouble with for some time. My heating system was new when the house was built nearly 8 years ago, since then I have had 2 pumps 3 new three way valves a new water thermostat and a new heat exchanger for the boiler which I fitted myself. The heat exchanger was supplied free by Baxi as I was told this type of boiler had a manufacturing fault on the heat exchanger. It would now seem the heat exchanger has again failed as the boiler is making some terrible noises like a kettle but 10 times as loud.

Do you think this is the problem and if so is their any way of stopping it happening again?

Stephen Boardman
January 2004