Been 12 months since we moved in here and inherited an right old system. Normal loft space expansion tanks etc with 25 rads of varying quality from okish to downright useless, replaced one as it had a pinhole, and a few others waiting in the wings for the same treatment. Anyway I digress, basically have just replaced the CH F/E tank. On firing up the system, a right old Camray boiler, seemed ok except very few of the rads got warm. Boiler kept cutting in and out as if reaching temperature setting. Noticed 2 things firstly the vent pipe into the new tank had disgorged a lot of brown water and that the Honeywell Automatic Air Vent EA122, next to the boiler was venting steam, not really sure what is going on here as all I have done is swap one tank for another. Any ideas?