Although you say that there is no oil in the coolant, or coolant in the oil, it still sounds like Head/Head gasket problem. Engines generally don't like being overheated.
Look for bubbles in the coolant. Radiator cap off (engine cold or removed very carefully), engine idling, once engine is up to normal operating temperature, ie thermostat open, look into radiator cap hole for bubbles going past (a torch may help). Geeves descibes another (probably better method) eslewhere on this site. Have a search for it.
Water pump. Whip the belts off and have a feel of the pump. They dont particularly fail as they are quite simple. It would have to have lost some of its impellor blades, be very rusty or have stopped turning to stop circulating water.
Whining sound may also be the turbo (especially if your vehicle has over approx 180,000 ks on it).
You may need to do a compression test.
Short term you can remove your thermostat to remove it from the equation.
Also sometimes after overheating sediment is dislodged from within the cooling channels/galleries that can block, or partially block, the radiator.
Aso you should probably have posted this in a more relevant/new topic. If I knew how to move it I would. Geeves may come along and do it.