I strongly need support in resolving a repeated failure of the electric coolant pump on my BMW X5 3.0si 2008.

About 2 months ago, the car experienced the continuous high fan revolution with the coolant light coming on.
Did some checks and found that the coolant is not flowing back through the top of the expansion tank and did a bleed, still no sign.
I immediately ordered for a new coolant pump from FCP Euro which i installed and worked fine but for 1 week, and the same issue re-occur.
I immediately ordered a fairly used pump and still the same issue re-occur.
I have ordered a new water pump from ebay part no. 11517568595; it is expected in next 4 days.

I need advice on what precaution to take in order not to have same issue on this new one.

NB. I use a second car connected directly to the battery to support the system while bleeding the coolant system