Just changed the radiator and thermostat on my xr3i.

Filled it full of water, then with the header tank cap off ran it for a couple of minutes to bleed itself. Havnt put antifreeze in yet as i was checking for leaks first.

Went for a quick run, pulled over to check the level, it was fine but seemed really hot for a short run!
Temp gauge is playing up, reads nothing then goes halfway then settles on a quater when i no its alot hotter then that so its hard too tell how hot it is.

Come home then let it tick over with cap off again as i thought it could have abit of air still left in it then all of a sudden header tank filled up an started overflowing!!
Turned it off quickly and it did it again! Is that just trapped air or is there a more serious problem?

It drives fine. I will say the other rad i had in had a crack in it and i was on a drive home about a month ago realised i had no heaters pulled over and there wasnt much water in it and as i had no temp gauge i didnt realise.
Don't no if this has anything to do with it?

Help please!!