If refering to the 200 series Rovers such as the 211,214,216 etc then the thermostat is in a housing beneayh the fuel inlet manifold, at the back of the engine at the crankshaft pulley end. access is limited so is sometimes easier reaching from underneath the car. it has rubber O ring seals.
The crankshaft sensor on a Rover 200 is located below and to the right of the generator and cylinder head temperature sensor. It is on the driver's side of the engine and above the oil filter.
NOOB
Located at the rear of the waterpump, under the inlet manifold
The thermostat is located on the front of the engine. Drain the water from the radiator. Remove the water hose. Remove the thermostat housing bolts. Reverse the process to install the new thermostat.
Follow the top hose from the radiator to the engine block. The thermostat is in the housing that the hose is connected to at this location
how do you replace a thermostat in a rover 25
Underneath by the radiator. White plastic bulb with three hoses on it.
It is located in a radiator hose, on a Petrol this is on the left side of the fan when looking at the engine.
Where the hose runs into the Engine behind the Distributor
Should be in a removable housing at the engine end of the upper radiator hose
where is the speed sensor on a rover 200
It is located at the bottom hose near the fan clutch on the right side if you facing the bonnet of the car