Its all the one system and all thats been done is bleeding to remove any air. What do you mean by back flushing? I thought that was the same as bleeding the system.
No mate, normal flushing and back flushing is not the same as bleeding.
Bleeding is a procedure where you follow the previous instructions posted to remove air from the system.
Flushing is a procedure where you disconnect the appropriate hoses and force water through the system ie Block, Radiator, Heater Matrix, Hoses, Pipes to remove any potential gunge which may be blocking or restricting the coolant flow. Usually the pressure from a normal garden hose will suffice.
Once you have flushed and back flushed and the coolant flow is as it should be then further bleeding will be required.