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Old 11-21-2020, 11:38 AM
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crystalworks crystalworks is offline
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Originally Posted by andrewwynn View Post
The difficulty is in that until detergent is used the oil will find high spots anywhere in the block and cling to things when drained. I don't think it's harmful to have a little oil so were it me I would do as described above.
Exactly. Last flush I did on a very dirty (rusty and oily) system I ran a few coolant system cleaners through with cheap coolant all the way up to temp. And then ran gallons (hose constantly on in expansion tank) while the radiator drain was open. Ran it for 30+ minutes until water coming out was same as water going in. Then shut off and drained the system and filled with distilled water. Then drained that and filled with bmw blue at 60/40 to compensate for some of the water still in the passages/block. Worked great, never had another issue with the cooling system on that car while we owned it.

It took a lot of time (whole process was at least 2 hours), but was probably pretty effective.
2005 X5 4.4i Build 04/05 Maintenance/Build Log
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