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      08-12-2019, 03:32 PM   #126
pbonsalb
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2009
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Drives: 08 E90 M3, 99 E36 M3 Turbo
Join Date: Feb 2011
Location: Concord, NH

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You donít need to bleed a high mount expansion tank. It is self bleeding. I donít know why it even has a bleed screw. Once the engine has gotten hot enough to open the thermostat and then cooled back down, you could remove the cap to release any air that migrated up to the tank.

Siphoning the expansion tank alone probably wonít lower the engine coolant level to below the thermostat. It should reduce the spillage. Let us know what you find. I have not read the whole thread but there is probably insight from others. I did this a year ago and drained the radiator. There is a drain on the lower driverís side. I did not have much spillage.