I have auxiliary water pump for the parking heater thee is dead ,but the prise one this one is 400 us for this small motor, I have found this hit on a Norwegian forum to modified this motor to fit, do any one have a tried this method
https://www.ebay.co.uk/itm/Additional-Water-Pump-PIERBURG-BMW-E38-E39-E65-E66-E67-X5-E53/283300860118?epid=1962358794&hash=item41f60c10d6:g:9OQAAOSwJ0xaWlX0
Link to this
https://bimmers.no/forums/topic/804299-webasto-diagnosefeils%C3%B8kingsp%C3%B8rsm%C3%A5l-samletr%C3%A5d/?page=11&tab=comments#comment-3160286
https://bimmers.no/forums/topic/804299-webasto-diagnosefeils%C3%B8kingsp%C3%B8rsm%C3%A5l-samletr%C3%A5d/?page=8&tab=comments#comment-3146187
do not try any modifications with these water pumps just pay the money and get it fitted for original if not you will regret it Bmw are bad enough for cooling problems let alone having to skimp out for a cheap part or compromise you didn't compromise when you bought it so why do it on parts