Hi all. Ive had to replace the pump isolator valves as they were leaking. All done and working but struggling to get air out. Rads are all good but when the boiler starts and stops there is odd sounds but mainly coming from inside the HW tank, sounds like water falling so im guessing air in the coil. There is what i think is an air valve near the 3 way valve but i dont get air or water from it. will attach image when i work out how. Any help appreciated.