Had new radiator fitted a few weeks ago due to transmission fluid leaking into the rad, it has been ok since and done a head gasket gas test with the blue liquid and that seemed to be fine however today the car has overheated badly, temperature gauge shot straight up to red and warning alarm sounded, opened the bonnet and steam was coming out, the radiator overflow bottle was full but water was not particularly hot. I left it 10 minutes and restarted the car just to get it home, the temperature gauge dropped back down to half and it seemed ok. Have got it home and it seemsok but just checked and the coolant overflow bottle is bubbling- I think the head gasket has blown? Any ideas?
Thanks, Dave