I don't know about bad for the car but it might not run well with a vacuum leak. At least cap the engine end of the hose on your way to the dealer.

This could be your cue to replace all the vacuum lines under the hood. See if your dealer can get line with the proper identifying marking. The dealer close to me doesn't stock line with color stripes and says it's more like $10-12/meter instead of $2-3/meter for plain white line.

Sixto
95 S420
91 300SE
87 300SDL
83 300SD