BMW Repair: overheating, bmw 330 diesel, head gasket

Question
Hi yes the fan is operating correctly. How does one check airflow through condenser & radiator. I have noticed that when hot the viscous fan & auxillary fan both operate & blow very hot air when you open the bonnet so hot that you cant even put your hand near it. Another thing I noticed was that after bleeding it again it was a little better in the sense that I dont have to put heating on too cool it down. It now fluctuates between half & three quarter mark on the guage with the a/c on full, before I had to put heating on to take guage back down to half way mark. Could it be airlock? Someone suggested water pump but it does not overheat without a/c also someone suggested possible lack of coolant flow through radiator. Please help.
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Followup To

Question -
Hi I have a BMW 330 diesel sport 2002 vin AW35834. Under normal driving conditions its fine but if I put the a/c to max and drive at cruising speed it tend to overheat. I have had the head gasket check, compression test and electrical diagnostic all was cleer. The thermostat and expansion bottle was recently replaced as expansion bottle cracked while driving.The viscous fan and auxillary fans were also replaced also the rad was checked for cold spots but was told its fine. Nobody seems to know what the problem is can you help?

Answer -
Having the fans(both) replaced makes me wonder if they are truely working.Does the aux fan run when you turn the a/c on?It should.Also check the air flow through the condensor and the radiator.

Answer
The coolant fow through the radiator could be the problem but mormally it would have to have mega miles and/or years on the vehicle.
Checking the air flow through the rad and the condensor can be pretty much visual,clean fins mainly,and the space between the condensor and the radiator.The correct coolant to water ratio is also important 50/50 max.It is a tendency to add just coolant to the system when it needs antifreeze,but when adding it should be mixed.