Rebuilding
the
Welch 1402
Vacuum Pump

Disassembly

(Revised)

D1

Remove the belt by loosening the set screw on the pulley attached to the motor using an allen wrench. If the belt is worn or it snaps while trying to replace it, replace it with a new belt. Belts can be purchased from Welch Vacuum or at an auto parts store, like NAPA.

D2

After the belt is off the motor please CAREFULLY test the motor by plugging in the vacuum pump and turning the motor on.

If the motor does not work the vacuum pump may not need repair, the motor may need repair or replacement.

D3

Use a wood block to prop up the motor end of the vacuum pump. Prop it up as much as you can because it helps to drain the oil in the next step. Draining as much oil as possible makes it much less messy when you open up the pump.

D4

Empty the oil from the vacuum pump by opening the valve on the oil reservoir. Turn the valve counterclockwise, right to left, to open it.

D5

Open the top drain so the oil will flow faster out of the pump.

D6

Remove the 4 screws holding the belt guard to the base using an allen wrench.

D7

Remove the 4 screws holding the vacuum pump to the base using an allen wrench.

D8

Tip the vacuum pump on its side.

D9

Remove the set screw holding the pulley onto the vacuum pump using an allen wrench at least 5.5 inches long. A longer allen wrench is fine, a shorter allen wrench wont reach. (Harbor Freight sells long allen wrenches)

D10

Remove the pulley from the vacuum pump.

Watch for the woodruff key underneath the set screw and put it in a safe place.

D11

Use a 0.5 inch wrench or ratchet to remove the bolts on the outside of the vacuum pump cover.

D12

Remove the gasket around the shaft using a flathead screwdriver.

D13

Also remove the seal between the gasket and the cover of the vacuum pump.

D14

Remove the cover to the vacuum inlet trap using an allen wrench.

D15

Check to be sure the screen basket (Air Filter) is not clogged and air can pass through it freely. A toothbrush lightly applied works well to clean the screen.

D15.1

Remove the bolts on the outside of the large end plate.

D15.2

Large end plate with bolts removed. It's hard to see but they are on the sides at the edge of the photo.

D16.1

Gloves on now please. This is messy. Remove the vacuum pump cover by gently tapping a piece of wood with a hammer, the wood will not damage the metal.

When the cover opens LOTS OF OIL MAY SPILL OUT.

Spread absorbent material all around the pump. Kitty litter also works as a great absorbent.

D17

Vacuum pump cover removed from back.

D18

Remove bolts from around the outside of the vacuum pump. The last bolt is underneath the pressure release duct. The cover will not come off until the last bolt is removed. See next step.

D19

Remove the top cover of the pressure release duct to remove the last bolt. You can see the remaining bolt in the top right of the photo.

D20

Carefully set aside the round metal ball.

D21

Remove the metal plate covering the end of the shaft.

Watch for a small metal disc between the end cap and the shaft.

D22

Remove the top cover of the vacuum pump, notice the rotating shaft and vanes spring loaded on the round metal pin (Spring Holder) which goes through the shaft, remove the exhaust ring.

D23.1

Before the exhaust rotor can be removed from the shaft, remove the 2 small vanes, then remove the 2 springs and then slide the spring holder out through the hole in the shaft.

D24

Remove the center plate using an allen wrench.

D25

To remove the final section go to the back of the large end plate cover and remove the bolts.

Remove the intake rotor the same way the exhaust rotor was removed.

D26

Soak the parts overnight in a large bucket of mild degreaser (Pine-Sol may work) to make it easier to clean the parts.