Had the classic hard brakes, no shutoff with key and lost doorlocks yesterday in my W116 300SD. I check all my vac connections and they are good, so I moved on to the check valve on the vacuum pump and saw this. Is it just an opening passage the whole way through. Is this normal, or should there be some kind of check inside there? I'm seeing check valves elsewhere that have something inside them.

My valve:

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'80 300SD - '83 240D - '00 E55 AMG - '02 G500