The big advantage to the 'pull' (vacuum) method is that it fits any sort of car, truck, or equipment that you may need to bleed without reservoir adaptors and such.

My vacuum device has outlasted the ownership of so many disparate vehicles, that I find this to be an important consideration.

Any air that comes in around the bleeder valve is outside(and remains outside) the hydraulic system, so it is not really a problem.

This can make it difficult to distinquish between air that was in the system vs. air that came in around the bleeder.
A little silicone grease on the bleeder threads will prevent this.

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1986 300E 5-Speed 240k mi.