Hello and Welcome to justanswer..
My name is MIKE - Im happy to help you with this...
The first thing that needs doing here is is to ensure that the expansion tank cap is in good condition - and renew it if in doubt. It has a pressure release valve in it which you cant do anything with if suspect -so it just has to be replaced. To be honest - I would do this right away given the situation -
IF then you still have problems - the next thing to do is to have the system "pressure bled" -- This is done with special equipment that most good garages have and it ensures that there is no air trapped in the system at all... this ruling that out. If that then cures it, you know thats it done.
If not - if you still have the same issues - then I suggest have the sensor for the fans renewed as that then would be seemingly faulty. At any rate , that then would be the next best / cost effective move - as the other suspects then are your head gaskets again - showing early signs of failure.
I dont really think from what you have said, that that is the case - It could be of course
but I have outlined the correct and cost effective way of working forward through this one for you. Im assuming it has been checked for any head gasket issues already.. so thats the way forward on this one now for you...
Let me know if you need anything more on this at all -
>> >> Meantime -- Please click on the OK rating to Excellent ratings service for me now, Thank you for that... and you can get back to me anytime if you need / wish..
Best Rgds, MIKE.
Please note, you are rating the content of my "answer" - my help to you - not the "system" which can experience delays etc which are not under my personal control -or delays caused by "time -off" which we all have on occasion - Thank you.