You can determine which sensor is setting off the alarm
with a meter. The switch in question will have a short across it's terminals.
What is the temp gauge reading when the engine
is warmed up? Up to 185 is normal. You said you have 100 kpa oil pressure when hot. If this is at idle, it might be OK. At cruising RPM
, that's definitely abnormal.
Don't take the thermostat out. It's the resort of all mechanics who have no understanding of how cooling
systems work. If the engine
you can change it.