Brute force vac pump purge

The Edwards EM 28 I use gets hella stinky in the oil. I change oil based on pull down to blank off. I inadvetantly stumbled onto what turned out to be sort of a brute force method of “cleaning” the pump out.

The Edwards manual warns that the consequence of overfilling the oil tank is that oil will then exit the exhaust during a run and make a mess. Other than that there is no inherent problem regarding operation. The sight gauge on the oil is hard to see and I inadvertantly filled the tank up to the top with Vac 20 oil after I drained a hot tank out.

So I put my large nylon hose on the exhaust as normal and fired up the pump. I immediately noticed the pump is MUCH quieter when the exhaust valve is buried in oil lol. Then, with hose plumbed out the door I opened the vacuum line to ambient and began pulling air through the pump. Oil could be seen blowing out with the air into the exhaust tube for several minutes then enough had left the tank it ceased.

I had been having troubles for two weeks getting the pump below 6 microns and historically an oil change in the pump would fix it. I had been running more terps into the oil than usual and it stunk. I noticed that after I overfilled then blew the oil out the exhaust from a full tank (rather than drain the tank down via the drain plug) that the churning action of the oil and all that air passing through a full tank had deodrrized the thing. I noticed an immediate return to factory specs on vacuum which I can measure at ¾ micron and the pump itself still overfull technically is very quiet.

No more oil blows out but then again my process create very little gas anyway to get blown out. The difference between properly full and full to the top must only be about half a quart or maybe a tad more. If I had a mist collector installed this would have been a disaster but I only run a straight nylon hose which is clear and can see the oil in it. Now if I leave the exhaust uncapped I smell no odor and before even after a change the room smelled gross with the oil uncapped.

For me I plan to go off book from now on and always overfill on a change and always plan a half quart sacrifice to get the stuff churning around in self clean mode. The instafix nature of the vacuum is reason enough if my oil is going to be catching volitiles. Vac oil 20 after delivery is about $60 gallon so it is a bit spendy but seems worth it to get the inside scrubbed out this way.


Sounds sort of like what people do to force purge the DuoSeal pumps by blocking the exhaust port with the drain valve open. Except… upside down :slight_smile:

Very interesting indeed!

Did you also have the gas ballast open when you were doing the “blow out” to clean the pump? I’m not able to get below 6 micron as well. I notice that my exahust smells when i have the gas ballast open even after draining and putting fresh oil in teh pump.

-So just to reiterate your procedure- just fill the tank to full full, connect a hose to the exaust, have the intake completely open to pull in air from ambient and then turn the pump on?

Thanks for the help!