Hi there, Newbie to the forum after buying my partner a 2002 Ford Focus Ghia with a 1.6 Zetec lump with 78k on clock. Anyway, the car over heated a couple of weeks after buying it and all the coolant p*ssed out the header tank. Refilled and all was ok for a while. Anyway, I had the exact same problems as you - the feeds to the header tank were just pumping boiling water into the tank and within minitues it was boiling up and out the cap. Spoke to Ford, no use other than some 1.6 engines can be hard to bleed, and can get airlocked up. So I replaced the thermostat (normally wouldnt go for a Ford part, but the motorkraft ones where the same price trade so fitted one), replaced the CHT sensor and also checked the following: [*]water pump good, all vanes in place and its not spinning on shaft [*]has a new drive belt anyway so not that [*]back flushed the coolant system inc cyl head to make sure no blockages [*]flushed the heater matrix [*]checked the fans - kick in fine at speed 2, not speed 1 (????) [*]gas tested header tank for compression gasses - none [*]pressure tested system - held pressure ok [*]no engine codes found in ECU or OBD2 other than 9318 (batt level, which may be due to stop starting, fans being on, A/c and lights on - so will clear and re-check after a good run) Anyway, new stat in place, with the system full of as much coolant as possible (but not overfilled in header tank - idea to try and reduce liklihood of air locks when refilling), it still over heated after 10-12 mins of idleing - rad hoses not getting hot, as system boils over before stat kicks in. Back of cyl head near matrix and DIS system getting very hot. Worth noteing to anyone interested - the Haynes manual does state that when refilling the engine on 1.4 and 1.6 you must back fill the head from one of the junctions located at the back right hand side. So, gave up, left cap off tank in despair for a couple of days, and just left the car. Restarted, to take it to garage, and all was ok from there - that was 1 week ago now. So either, the system had an airleak which cleared over the 48 hours when left outside in the cold or, its entirly unrelated and will boil over again soon!! Two things that I cant understand which I hope someone can help with: 1) why the engine boiled over initially - if it is an air lock, how did it get there in the first place (nb - unless head gasket gone and blowing compression gasses into coolant system) 2) why does the rad fans (speed 2) some times come on when I turn the interior fans on to setting 1,2,3 or 4? These should be unrelated surely - maybe a red herring but I need to look into this more. Just wanted to share my findings with the aim that the collective thoughts may result in some good findings!