There is oil in the pump and sometimes it comes out. Before we get
all excited, lets check on where this oil is coming from. Sometimes
it is a function of the pump operation and can be considered normal.
It is a good troubleshooting mechanism to take a section of the local
newspaper and put it underneath the pump. The leak will become
apparent within a short period of time along with the general area of the
Common leaks order of commonality
A. Shaft seals and lip seals. These wear out and then can leak.
This is one of the weakest links on a vacuum pump relating to leaks and is
usually repairable with some modest effort. HyVac belt drive pumps
mostly use an externally mounted shaft seal and we are talking about
replacing 4 screws so not a big deal. Most direct drive pumps you
have to take off the motor and take apart the pump to get at the shaft
B. Gaskets and O-ring. These usually hold up but a repaired pump or
one taken apart usually needs this item replaced. If the mating
surfaces have a nick or a burr then this can also contribute to a leak.
When a leak is not a leak.
Sometimes high vacuum pumps are run at high pressure (low vacuum).
They don't like this. This
then creates oil mist and oil agitation in the pump. This oil mist can
collect in the exhaust filter or dome on the exhaust port. It
coalesces and drips down the side of the pump. This is often
mistaken for a leak but really the user just needs to either stop the air
leaks or buy an upgraded exhaust filter to correct this issue. This
can also manifest itself by blowing by O-ring or grommets.
Another potential solution if the oil is simply splashing out the exhaust
port is to raise the exhaust port up like 6-8 inches using pipe fittings
or vacuum fittings. This at least gets the exit point away from the
splashing action going on in the pump with the high gas flows.