Boiler overheating and making noises Vaillant VCGB 112/142EH?

Had a new 3 port valve changed as radiators were coming on at the same time as water even though only water was on. However recently the boiler has been making awful noises ... had serviced and noticed water was a lot hotter but still making noises. Gas man turned pressure from 7 to 4 and now still making noises but the water and radiators are no where near as hot .... he is stumped? Any help would be appreciated