Your radiator shop guy will be able to ID oil sludge / HG problem from your old radiator. Try a 1/16" hole on the flange of the 'stat and orient that at the top. It will aid bleeding a lot.

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Good - Fast - Cheap: Pick any two.
Current:
E23 735i; E30 318i; E32 735iL; E38 735iL; R50 Cooper; R55 Cooper Clubman.
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E21 318i; E32 735iL; E34 535i; E38 730iL; E53 4.4i