85 300DT, or D/T or D/Turbo.. whatever you want to call it

Anyway... speaking of vacuum.. if I lock and unlock my car more than 3(ish) times without starting it, the other doors stop locking... do I have a vacuum leak or is this all I should expect?

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1985 MB 300D/T

Fell off the WVO bandwagon when people started trying to charge $2.50 a gallon for dirty vegetable oil.