So I sat idling for a while (30 minutes, traffic queue) yesterday and I didn't notice the temp LEDs going north. They reached the 3rd from right before the rad cap decided to turn into a kettle (literally whistling) and vent 4 litres of water onto the road. No warning beeps, no water level warning - nothing. I turned the engine off and rolled it to the side of the road for 30 minutes, added some more water and she fired up and drove home just fine, no overheat, no extra rattles or knocks, oil reached 115 so was probably doing the bulk of my cooling. I'm hoping no damage.
When I got home I saw the drivers side rad fan was spinning slowly (quietly) so I know that works, and the passenger side one was not spinning but was free to do so - so I'm a bit baffled as to why it's vented its guts. I idled it in the drive for 10 minutes and couldn't get it to repeat the problem.
I'll check the usual (fan stats, both fan function etc), look for pinhole leaks with a UV dye, but is there anything commonly known on these that would catch me out?
Cheers