Test 1 complete: Thermostat removed and tested in a pan of water brought to the boil.

Good news: no sign of the inside seal breaking up, which is good because it might have meant bits of rubber getting into water ways in the engine or radiator.

Less Good News: No sign of the thermostat starting to open at 100C, and it should at least have shown a bit of a sign of moving if it's supposed to be fully open by 105C. Still, at least it does give a clear indication of a fault and I've got a new one due for delivery today.

[Linked Image]

Tim H.
1986 4/4 VVTi Sport, 2002 LR Defender, 2022 Mini Cooper SE