How to Maximize Vacuum Pump Life

From Rapco website www.rapcoinc.com/vpump.htm

As seen in......
REPORTER Issue 6
January 1, 1995

    We often see pneumatic pumps coming to us for overhaul and warranty consideration with Teflon tape in the inlet and outlet ports, and all too often, wedged between the cavity wall and the rotor.
    As thin as the tape is, it will not pass between the rotor and the cavity wall. Statements have been made that you can use this tape starting at the third thread on the fitting. This sounds logical, however, many of the inlet housings have only four threads on the inlet Boss with usually 9 threads on the 200 series pump fittings and 8 on the 400 series pump fittings. Unfortunately what will happen is the fitting is threaded on far enough to allow the Teflon tape to be exposed to the airflow (see the cutaway at right). It is only a matter hours before the tape tears off and renders a new pump useless.
    We also see fittings and gaskets with tite-seal or permatex on them. When these products get hot, they run. As the pump is a low pressure environment, this fluid is drawn into the pump and onto the rotors and vanes. If the rotor does not break, it will have enough sticky substance present to prevent the vanes from moving in and out of their slots. Always use silicone spray on the fitting threads, let it dry and install the fitting.

When replacing the original pump, check the following:

1.     Is there excessive oil present when the pump is removed? If so, the engine probably has a leaking oil seal. It should be replaced before installing the new pump. If it is
not the accessory pad seal that is leaking, check for an external engine oil leak that airflow can bring to the pump.
2.     Check the hose that came off the fittings for any frayed material or small pieces of rubber that may break loose when the new pump is installed. You also will want to
check the hose at the filter end when you change the filter. You should always change the filters after a pump failure and blow out the hoses. Small pieces of carbon can remain in the hose, and may be drawn into the new pump on start up. Don't forget that when a pump fails, the carbon particles can go both upstream and downstream. The whole system should be cleaned. The downstream filter stops carbon from going into the instruments. If the filter is not changed when the pump is replaced, the carbon could go back to the pump if the engine kicks back at any time. When performing this procedure, blow air from both directions - a bit of debris may lay in low areas such as hose
connections and firewall fittings. NOTE: Be sure that you don't blow into a line that is going directly to any instruments. Destroying an instrument will ruin your day.
3.    Replace old, hard or brittle hoses. The inside rubber may break up and enter the pump. This is particularly true of hoses near turbo chargers. The best test to determine if the hose is deteriorated is to flex and bend the hose while holding an end over a clean peace of white paper or paper towel. If you see debris fall onto the paper, replace the hose.
4.     Cover the pump when washing the engine. Solvents will thin out the oils on the engine and make it easier for the fluid to get into the pump through the mounting area and pass the drive finger and bushing. The bushing mounted in the base is a carbon graphite mix, and when the graphite gets oil contaminated, it will swell in size and tighten onto the drive finger causing failure. Aluminum foil can be used to cover the pump and mounting flange.
5.     If the hoses are going to be disconnected for an extended period of time, cover the end with tape to prevent any debris (including cleaning solvents) from entering.
6.     Complete and register the warranty cards immediately. This is true for all new or overhauled vacuum pumps. The denial of a warranty claim because the part was not
registered will most likely get the unwanted attention of the person paying the bill !

For Experimental Engines

1.    Mount the pump so there is no side load on the input shaft.

2.    The pump develops enough output at 2100-2200 RPM.  Set the drive up to run 2400 RPM during cruise.  Extra un-needed speed shortens life.

3.    Keep it Cool.  A cooler similar to the RA28 can increase life.

4.    Keep any oil away from it.

5.    Change filters often.