520i e34 overheating

[dwaynos]

hi,
my 520i is overheating and i dont know the cause. It over heats as if it were the headgasket it takes average time to get the the middle then stays there for a few minuetes and then quickly goes to red then stalls. I have checked the water pump and it seems ok. i dont think it is the headgasket because it has no other symptoms to say. the filler cap is not white and neither is the dipstick. i dont think there is oil in the cooant but i cannot check anymore because i drained it. Im not sure about the thermostat but im sure u will be able to help me on that one. the only thing i can think of apart from the thermostat is the coolant circuit needs bleeding, what do u think.
ALL THIS HAPPENS WHILST IDLEING

thanks in advance

[whiskychaser]

hi,
my 520i is overheating and i dont know the cause. It over heats as if it were the headgasket it takes average time to get the the middle then stays there for a few minuetes and then quickly goes to red then stalls. I have checked the water pump and it seems ok. i dont think it is the headgasket because it has no other symptoms to say. the filler cap is not white and neither is the dipstick. i dont think there is oil in the cooant but i cannot check anymore because i drained it. Im not sure about the thermostat but im sure u will be able to help me on that one. the only thing i can think of apart from the thermostat is the coolant circuit needs bleeding, what do u think.
ALL THIS HAPPENS WHILST IDLEING

thanks in advance

Overheating on idle is enough to kill it. You cant diagnose a fault in a cooling system if you dont have coolant in it but in the meantime:
Has it just started doing this?
Are you losing coolant?
Does the heater get hot?
Er... why not try bleeding it?
Was the coolant black when you drained it?
How did you check the pump?

[dwaynos]

thanks for the reply
the coolant was not black when i drained it
i checked the pump by removing it it has a plastic impeller but looks fine it is not damaged
how do i check the viscous fan is working could that be the cause and how much would one cost?

thanks