Boiler issue with radiators only getting luke warm Help and information on all topics relating to your central heating, air conditioning and ventilation issues.

[Buggsy01]

My daughter just moved into a house with a 7/8 year old Baxi Duotec combi boiler. I changed all radiators, fitted trvs, renewed some piping, fully bled all radiators, then balanced the system. The boiler was noisy and all radiators were only getting lukewarm. If the trvs are fully open on any 2/3 radiators and the rest closed, they get very hot but all wont get hot together. Called Baxi out via a repair plan and they changed the diverter valve but the return wasnt getting hot, then said that the heat exchanger was furred up and the system needed a flush by a heating engineer (quotes £800 ish) or the boiler isn't covered - this isn't covered on the insurance. Ran the boiler for 2 sessions of 5 hours and it's much quieter but all radiators still only get lukewarm. One thing that I have noticed is that when the boiler is on (pump running) the system pressure drops about 0.5 bar. Turning the boiler off and the pressure rises to normal. Could this be a pump issue ie not having enough flow or pressure to satisfy the whole system at once.