Proper powerflush will do the job, absolutely no need to change the boiler by the sound of it.No, not leaking - but engineer is saying (I think) that if it's sludged up (not completely, as heating/water is working) or limescaled then need to power flush entire system, or rpleace boiler, which to me sounds excessive.
The question I would ask myself: "If it takes me this long to come to a questionable solution, do I want this company to powerflush the system?"
Thanks for your kind reply. Apologies for troubling you further, but assuming the problem is correctly identified as sludge in the heat exchanger, isn't the best (and cost effective solution) just to focus the cleaning effort on the heat exchanger ?? Or is it a massive job to remove & refit heat exchanger, and so more expensive than power flushing the whole system (for £600) ?? Thanks & best wishes !! David