Vacuum pump oil question

[Tris]

Good morning all,
I'm hoping someone in the know can advise me on this. I have been given an old Genevac vacuum pump, which has been sitting around for some time. As part of building a vac chuck system I thought it would be a good idea to change the oil. Opened up the drain plug and yes, the oil was grim.

Now comes the question, as there is no obvious filling point does the oil go in the pump inlet?

 

[ChaiLatte]

If what comes out the drain hole needs to go into the pump inlet, push some back into the drain hole with a syringe, reinstall the plug and turn the pump upside down. If what you have added pours from the inlet, the two holes are connected.

A more refined version of this might be to shine a light into one of the two holes and see if it is visible through the other one.

Have you searched for a manual using the model number (illegible in the photo)?

 

[Tris]

No luck finding a manual, it's model number is NRS.2. Will try tipping the thing over and see what comes out.
What little oil was in there was well below the sight glass and not visible even poking an endoscope down the inlet. Probably worth a flush through while I'm at it