Because the calipers were being compressed (driving the fluid back to the reservoir), it was necessary to remove some fluid to prevent it overflowing. But because it's so black (indicating that it's extremely old, and has probably never been changed), it was all removed and the reservoir washed out.
IF THE IMAGE IS TOO SMALL, click it.
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The red cruise deactivator switch on the MC is dangerous, but any Ford dealership should replace it free under recall 05S28:
R&I and clean brake fluid reservoir; clean master cylinder wells; clean & lube reservoir grommets; supply & install new DOT3 fluid $50 (done)
