BMW 325i, M reg.
A year or more ago I changed the radiator (GSF or Euro Car Parts) and the coolant level sensor was a sloppy fit on the threads so left the blanking cap on. Recently discovered I was low on coolant. Topped up, bled, topped up until I'm pretty sure I've got no air locks but........
After a run top hose is too hot to touch for more than a second while the bottom hose is barely warm but temperature gauge never moves above the point it always has sat at.
First thought was thermostat stuck closed but wouldn't that send the temperature gauge high? I know it sounds lazy but reluctant to change the thermostat in this weather if I don't need to. Can I trust the temperature sensor?
Regards.