I needed to fault-find a possible flow issue, and after cocking up with the drill press, this was my next best option. Don’t worry though, there’s a new one coming on Monday.
After testing it in water which was at a rolling boil, this was the maximum aperture on the valve.
The spec sheet says it should be 9mm+ after 88°C, which this is not - and would you just look at that wonky spring!
You may be asking why I didn’t just pull the thermostat all together instead of hacking its guts out. It turns out that the rubber gasket which fits around the outer diameter of the thermostat doubles as the housing gasket, so I needed something in there to keep it all tight and tidy.
And then in true racecar fashion I fitted the bottom radiator hose clamp incorrectly and almost blew the engine on a spirited test drive. Stupid is as stupid does, and unfortunately my cars suffer immensely for it.