Vac/Modulator

1987 420SEL 222,347 miles
What if any harm can arise from minute traces of fluid in the plastic vacuum line leading from the engine to the modulator. I disconnected the line at the modulator and allowed to drain towards the ground. Total removed was about three to four drops. At this time I suppose it would have been wise to capture the drippings on a piece of white paper to determine it`s origin (engine oil/tranny fluid)!!
This is the second time in three weeks that this has occurred and it has me thinking maybe a change of t/modulator though only last year the new style was installed and yes the transmission shifts ever so smoothly.
The tranny/modulator was calibrated and set at the MB dealership. A wi$e inve$tment.
On a second note. What can I do to plug up a leak in my exhaust at the cat where the two pipes go into the cat. The leak is dead center between the two pipes as they converge into one. Would welding the small (3/4") seam (opening) do for now or perhaps some type of patching material. Plans are to eventually replace the cat just before inspection and other work is completed.

[Benzmac]

If the crank case vent is clogged, it will cause this. This is the hose that goes from the driver's side valve cover to the engine. The hose connects to the engine via a alumminum block. That block has a small hole in it that will stop up. Use a sharp pick to clean it and some carb cleaner.

Thank you for your earlier reply Benzmac.
A few more related questions for the Shop Forum

How would the crankcase/vent blockage influence the function of the vac/modulator? Is the vacuum flow lesser or greater? What is the correct direction of flow at the vac/modulator to the vac/line? The restriction you mentioned in the earlier post is troublesome because of other possible points of origin. Is it possible one could be the idle air valve though recently replaced and all rubber hoses cleaned?