Do Trico Vacuum Motors leak???

[cjc56]

I am looking for a vac leak in my 56 Tbird. The last thing to test was the wiper motor. I found that the motor (when in the off position) does not hold a vacuum. I would think that that means it is leaking when in the off position. Is anyone familiar when these motors and is it normal to leak in the off position. I have 2 of these motors which I have tested and both act the same way. They work great otherwise.