Hiya folks will describe this best I can, For a while now when starting engine from cold I can hear water swishing about which I suspect as heater matrix but goes away when warmed up, Expansion bottle rises and falls as engine heats and cools, heater blows hot air ok, never over heated, car drives fine and no white smoke ect. Now worrying bit, when warmed up and looking in expansion bottle at battery there is bubbling every couple of seconds, when the engine cools down the water level in tank at turbo drops down i reckon about 2-3cm from top and top radiator hose feels like its empty when u squash it i.e water in tank at turbo hardly moves. Started it this morning with the tank cap off and noticed loads of bubbles in the coolant as it started to expand then after driving it back home I found the top rad hose burning hot to touch yet the bottom hose was stone cold, so i though maybe thermostat stuck but the heater works fine which implies there is a coolant flow also there is no signs whatsoever of emulsified oil. It was in for timing belt/pulley replacement about 8 months ago so hoping a air lock could be causing these problems but I have tried to prime the system but doesnt seem to help, maybe a full coolent flush and clean help? I guess the next step will be to get a hydrocarbon test done on the coolent. Guess I am hoping someone here will say nah its not head gasket its this ..... lol