Charles, I would suggest checking all of the vacuum lines especially the ones going to the vacuum control valve on top of the IP. I had a leaky transmission vacuum assembly which was sucking trans fluid into the vacuum control valve. It would have eventually filled all of my vacuum devices if not caught in time. Follow the vacuum line down to the transmission. On the passenger side, find the vacuum valve, pull off the vaccum hose and see if you can feel any fluid leaking. Just one notion.
Cheers my friend, Patsy