Water hammer and boiler going out

[mattrobins99]

Hi all, we have a weird problem with our boiler/plumbing (not sure which) and I’m getting different opinions on what might be happening, so thought I’d run it past here before we start spending loads of money on boiler repairs that may not fix the problem. So here goes:

A few weeks back we started hearing a weird whining noise coming from the boiler and noticed that if we tried to run a bath or two taps/the shower at the same time, i.e. lots of hot water, the boiler would go out and making a banging noise for a while, I guess trying to relight itself and the water goes cold for a short time. So, we booked a boiler service assuming it was at fault; however, we’ve since noticed that the whining noise is now coming from the kitchen sink, far away from the boiler. For example if we flush the downstairs loo, the pipes around the kitchen sink whine and a little water dribbles out of the kitchen tap at the same time. All very bizarre.

So, the heating engineer serviced the boiler and I relayed the story but he is convinced the problem with the boiler is that the heat exchanger needs replacing. He pointed out that the water runs very hot, which it does tbh. He also said the noise was probably water hammer - I’ve done some googling and it seems likely this is the case, but I also get the impression this could be caused by high water pressure. It seems a coincidence that the boiler started playing up around the same time as the water hammer started. Oh and my father in law reckons it may be the thermostatic water valve at fault.

So the question I guess is whether we go ahead and replace the heat exchanger and see what happens or focus on the water pressure? Any advice would be gratefully received! Thanks in advance.

The boiler is a Worcester Bosch Greenstar 28i Junior boiler