Generator Cover
 

What is this hole in the cover of the ec300 2018 generator for? A friend of mine took off this cover and saw water and traces of rust inside, he wants to seal it so that no water gets in. Should I do it? Possibly water gets in from above through the seal ...
https://i.ibb.co/nbKWh3C/photo-2020-11-16-10-11-50.jpg
https://i.ibb.co/TkfFjf5/photo-2020-11-16-10-12-28.jpg

Pressure reliever. Condensation can form inside the cover when the engine gets hot and the outside is cold. If you block it, you'll need to put a relief valve somewhere else to compensate.

You can block it off and add a small amount of oil. It will probably need a breather up the top though. Betas do not run one though so you might not need to.

We did wet mod on mates 15, same drain blocked up, small amount of fork oil to lube bendix.
Blew oil out a bit.

Grease nipple fitting opened up up top of case. Hose run upwards. No drama since.

Ditto on the posts above. You don't want to block it off (unless you do the wet mod) because if you do, water can't get out and it will rust more inside.

I did the wet mod as the others suggested. Seal up that hole. Take the Bendix cover off, and put 2 oz. of 5W fork oil into the stator cavity. Then for a vent or breather at the top I was able to take a barbed plastic drip irrigation fitting and push it through the rubber grommet where the wires go through (see your second picture), and then added a hose that vents up under the tank.

The common way to do it (as others mentioned above) is to drill a hole in the top of the stator cover and tap threads that will allow a small fitting or grease nipple (as F5 said) to be screwed in, to which a vent tube can be attached.

fyi on another venting idea,

Jeff

I understood everything, thanks to everyone.:)