ok this is low coolant warning part 250

ok so my situation is my car cant hold the coolant for around 6month to a year and then it will leak ..it been like that for the last 5 year ... they were changing tthe water pump and then 8-12 month later boom, radiator, another 10month boom, water pump ... add another 10month and then the expansion tank etc etc etc

lastt winter i thought the problem was finally resolve... the garage find out that the atf was clog due of too much k seal...

and now 8 month later guess what.. boom again... so now i suspect that there is some k seal still leftt in the system or another part being clog... is a coolant flush gonna work ??? or im pretty much screw ?? and have to take apart every single piece of the coolalnt system and check one by one

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BMW X5 3.0i 2006