Since my original post, I called Mityvac tech support. I described my situation and they confirmed that, yes, you pull out all the coolant through the expansion tank....and that you'll actually see the hoses collapse as you're doing it because of the vacuum that's created,

So, as I understand it, here's the procedure:

1. Remove expansion tank cap.

2. Insert Mityvac tube into expansion tank and begin extraction until no more coolant comes out.

3. Fill expansion tank.

4. Turn engine on with heat on.

5. Continue feeding coolant into expansion tank as it drains into cooling system. Should take 10 quarts altogether.

Does that sound right? Anyone see any downside to this procedure?

CORRECTION...THIS IS INCORRECT, SEE BELOW

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14 E250 Bluetec 4Matic "Sinclair", Palladium Silver on Black, 159k miles
06 E320 CDI "Rutherford", Black on Tan, 178k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver on Tan, 145k mi, wastegate conversion, ALDA delete

19 Honda CR-V EX 75k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife