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BMW says the following regarding their pumps- "Original BMW Water Pumps remain absolutely reliable even under extreme temperature conditions. Tailored to the specific engine, precisely machined and intensively tested, their main distinguishing feature is a long service life. Even at 7,000 rpm and after 100 hours of continuous testing, they must lose no more than 12 grams of water. So the only time that you will see an overheated engine is when you pass one".
From this, it appears that the pump itself is quite reliable but the electronics driving it is not.
BTW, this is a standard test on water pumps and is known as ASTM Test D2809. The test is run at a temperature of about 113C (235F) and mainly tests for cavitation (formation of high pressure gas bubbles that can create pits in the pump material and lower the cooling efficiency by decreasing the contact area with the flowing liquid). Such a test may not have tested the electronics. If there is a way to change the electronics alone, then the expense of water pump replacement can be lowered.
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