While diagnosing a problem with the vacuum pump I tested the main vacuum line to the booster by disconnecting the line at the booster and connecting my hand pump there. I was able to generate a vacuum in the door lock circuit (via the connection from the booster line) by pumping from the nut where the line connects to the booster.

I'm not too sure about how the valve in the booster line works; am I supposed to be able to pull air out of the door lock circuit, through the valve, back in the direction of the booster? It seems the valve is there to keep this from occurring.

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'Betsy the Getaway Car' : 1978 MB 240D, 582k
'The Mistress of the Sea' : 2001 Giant Boulder, 10.30k