I am looking for some advice on how to cure our very noisy central heating system which is driving myself and the whole of the family up the wall (excuse the pun)!!! The system is a open vented, gravity feed central heating system. It consists of a Glowworm gas fired boiler in the garage, wilo gold circulator pump (replacement for a Grunfos 15/50), Sunvic 3 way motorised valve, HW tank thermostat, sunvic programmer and sunvic programmable room stat. The circulator and motorised valve are in the airing cupboard upstair with the hot water tank. The noise starts when the heating (or hot water) switches on, the pump starts up and the system sounds loud, once the bolier has heated the water up there is a very large "whoosing" sound in the airing cupboard followed by what sounds like a rush of water through the pipework - if you hold the pipe that feeds up to the pump it instantly gets red hot after this noise has occurred. The note of the pump then changes and it gets louder. When the system is calling for heating there is a sound of running water in the pipework feeding the radiators and in the radiators themselves there is a bubbling noise that can be heard. I have bleed the radiators and no air escapes just water. As the system runs the whooshing noise continues and the whole system sounds like it is going to take off!!! No work has been carried out on the system for about 18 months when the pump and 3 way motorised valve and head where replaced requiring a full drain down. When the system was refilled I was careful to make sure I bleed the system to remove air. Last time I was in the loft by the f&e tank I noticed there was water coming from the expansion pipe looped over the top of the tank and also noticed a brown scum on the water in the f&e tank. Airing cupboard is located about our lounge so the noise is very noticable and drives everyone mad when trying to have a quiet night in front of the box. I have tried to slow the pump down from number 3 (the grundfos was always on 3 since we moved into the house 10 yrs ago) to number 2 and this has made a slight reduction to the noise from the pump but the other noises far outway this. Any advice or DIY tips would be appreciated.