Brian.
It wont be head gasket (symptoms also confirm this), also, you will loose coolant if it heats to the point the fans come on as there will be areas in the engine at greater than 100deg C so you get local boiling (as the cap is off and there is no pressure in the system).
Out of interest, why did you change the coolant (as its only circa 1 year old so should be good for another 2-3 years)?
Key question is, with the cap on and under normal use, do you lose coolant?
Mark
hi mark,changed coolant cause sure someone said to try as temp gauge causing some ups and downs , anyway started writing this nearly at end and pressed wrong button anyway here goes, spent a while a car today, the start was fine but temp gauge takes a good few minutes to rise when it does it goes to about 85 ish and with air con on heat comes through, after running for few minutes the temp gauge drops to 80 or just above and remains there while on move until slowing down for r/bout or traffic then heads up to 90+ fans kick in and then drops to normal 85/90 but when driving on drops to 80+ again while this happening the heat often stops and you get bit cooler air coming through and then history repeats every time slowing etc until you stop and it sits anywhere between 85/90 but occasionally either heads up or down.
now the coolant, no loss when running etc and when changed I made sure over period couple days to check level was where it should be but around same time temp gauge started being funny the coolant started to rise in tank by about a inch or so above max,yesterday I took some out with syringe thingy back down to max level ran for while but then back to about a inch above max so today I opened cap and then red valve and let out a bit which took expansion tank to almost bottom and then ran engine with blowers etc on hi till temp up for fans kicking in I burped the hoses a fair bit and no difference to level so I filled to max then put cap on and tick over for few minutes till fans kick in again which takes ages with this temp guage not sure where to be, anyway it may be me but before and I mean before these happenings when you loosened off tank cap when hot you did so very slowly for pressure but today even with everything hot cap came off with no hiss etc like no pressure. the level still sitting same at mo at max.
and just to add to the confusion the oil I have a leak somewhere to right side/front as wet behind pulleys and right side below black covers and just above heat shield. the oil level is weird also when checked it was in middle dipstick before but now its hard to get definite line it seems to be low but after running a while it the shows some above top level but again no definite mark there is a fair bit smoke coming out dipstick tube and when you open oil filler cap. I hope this makes sense to you thanks and can I just add since then fuel dropping to average 16 in town and run to Bedford and back on decent road 20.9