I have been off the road since 19th March with a broken foot, left her running maybe 5 or 10 minutes and this happened for the first time ever,,,,,, went to check the fan belt was ok after typing that,,, the chuffing fan connector had come off??
Quote; “ Left running maybe 5 or 10 minutes and this happened for the first time ever”
Idling boiled in 10 minutes?
Water stat stuck closed, pump not turning or rad gunged up ( rad weld )?
My three ancient K11s used in 14 years have never run the rad fans & never overheated in normal driving even when stuck for ages in frequent M5 motorway traffic jam tailbacks.
Hard to say what temperature it got up to, but I don't think you'll have done much damage
I know that with the radiator cap off it will boil in about 10 minutes but water boils at higher temperatures with more pressure like with the lids on, but of course better not to have a rad fan than to not have fluid in or be ragging it at the time or something