HOW COOLANT CIRCULATES AROUND THE ENGINE
How the 200 / ZR cooling system works, The water pump first pushes coolant..into engine block which then flows into the cylinder head getting hotter as it circulates, hot coolant then exits from coolant elbow, front right hand side of the cylinder head along top hose then into radiator to be cooled, then out of the bottom hose up along the coolant rail to the thermostat, back to water pump, constantly repeating the cooling process.
In convential systems, the thermostat is most usually located on the..outlet from the engine, the unusual location on the K Series being at the rear allows engine to reach its temperature much more quickly and evenly with short periods of opening and closing.
Cold coolant coming in by stages allows the engine to retain its heat while it gradually reaches its normal operating temperature, and so avoids stressing the casting through a sudden heat shock, the cooling system, under normal driving will heat up very fast. This could have its problems not allowing heated coolant to flow around fast enough.
The lack of a constant coolant flow in an engine that is working hard from cold, could in some case's be a possible contributing factor in head gasket failure HGF overheating in the cylinder head. A good reason to keep my engine speed at a maximum of 2500 rpm or even lower until its fully warmed up, which in these cars is fast and very good.
The 200 / ZR will achieve this very quickly indeed, usually within the first mile or even less, a well maintained cooling system may have warm air just slightly evident at the face level air vents in as little as 0.2 tenths of a mile, the first signs of a warm up process and should remain constant throughout the year, including all extreme cold temperatures.
A coolant circulation check is to feel the radiator top hose it will be hot, and radiators bottom hose should be warm after coolant has been cooled prior to it going back into the engine to continue on its constant re-circulating cooling process, air entering the vehicles front meshed grills during foreward motion is sufficient for normal driving cooling purposes.
Cabin heater, or heater matrix, is basically just a smaller version of the cars radiator, is filled with hot coolant supplied via the smaller of the two elbow joints coolant hose, which then feeds hot air into the cabin as and when required, and is located in an enclosed area between the centre console and engine bulkhead, the matrix heater does not require any form of air cooling properties, as this is not really necessary.
The electric fan will activate to give additional faster cooling during any prolonged periods of engine idling, Its worth taking note, the temp gauge needle which on these models are usually showing a tad below half shortly after commencing a drive..will not always mean that the engines actual operating temperature has yet been fully reached.
When the cabin heater control knob is rotated fully to the cold position, the heater control valve located on the bulkhead will close, so as not to allow any amount of the engines hot coolant to circulate within the heater matrix, so now only cold, or cool air comes into the cabin.
Rover 200/MG-ZR Technical and Information Pages (c) 2004-2018.