Hi I have an 08plate Fiesta zetec automatic.  She has a habit of over heating.  She has always had a good heater on her but recently she has started to overheat and boil over but the temperature dial does not go up form halfway.  She's had her fan changed as it had stopped work, we have also changes the water pump, the cam belt, thermostat and the water bottle has been changed.  Her radiator has been flushed and cleaned twice.  But despite all of this she is still over heating.  When driving I can hear water sloshing around the front bulkhead and occasionally a rumbling fan noise.  There is no water in the engine as the oil is still clean.  Can anyone think of anything I have missed.

Water sloshing behind the bulkhead means there is still air in the system so coolant won't circulate effectively.

It may just not have been bled properly after the previous work.  Or there may be a small leak somewhere.  Or the headgasket may have failed.

If you can get a CO2 sniff test done on the coolant that rules out the headgasket.

Next test would be a coolant pressure test to see if the system loses pressure over an hour or more.

If the headgasket is fine and the pressure doesn't drop then it just needs bleeding properly.