BMW: Overheating, temperature dictates, upper radiator hose

Question
Overheating problems on my 1997 BMW 528i tourer automatic. I have had the radiator, thermostat and waterpump changed. The cylinder head has been inspected - ok. The heating system has been backflushed. When the engine is running on tickover, temp is ok. When running at higher revs it overheats. Is it anything mechanical and how do you bleed the system properly.

Answer
Tom,
I would suspect the fan clutch that screws into the water pump is not locking up as it should or the electric fan behind the grill is not turning on when the temperature dictates. Or as you suspect the engine has just not been bleed properly. To bleed the coolant open the plastic philips head screw on the thermostat housing next to the upper radiator hose and the similar screw next to the radiator cap. Fill the coolant until it errupts from the thermostat housing then tighten the screw back down-lightly as it is plastic. Then continue to fill until the same happens at the other screw then tighten is down. Then start the engine and rev it until the coolant level drops and top it off. Screw the cap back on and it should be bleed. This may need to be repeated after the engine has cooled. Be very minfule of the coolant with the engine running as it gets hot quickly and be prepared to clean the mess promptly.