I have the old brass type, repainted black. We made thousands in the radiator factory I worked at in the '80's. I could probably do without it on the Plus8 but it is handy when changing coolant. It can be raised up to help airlock removal.
It is handy for checking the level but luckily(?) I reckon only having to top up with extremely little volumes of coolant.
Tempting fate perhaps but no coolant loss.
