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Projects - Rebuilding Diesel Vacuum Pump

By: Steve O

My project truck had some REALLY stiff brakes. If you have to stand on your brake pedal to make your diesel stop from a slow speed, you'll want to look into doing this rebuild. I also noticed that the vacuum actuated heater box didn't work either. Figured it was a failed vacuum pump.

First, remove the vacuum pump from the car. Follow the procedures in the shop manual for removal. 13mm open ended wrench is what mine used to remove it. You'll need a screwdriver to remove the hose clamps as well.

I spun the bottom gear a few times after removal and there was NO resistance at all.

Tools:

10mm nut driver or socket
Flat blade screwdriver
90 degree pick tool
Putty knife
Wire brush (for cleaning any parts)
Shop rags, paper towels, etc
Nitrile / Latex gloves
Anti-Seize paste
Cleaner / Degreaser
Vice (help to hold the sucker in place when trying to get some screws out)

Parts:
Vacuum pump rebuild kit. There are two of these. I just opted to buy both and do a complete rebuild. Both rebuild kits come to less than $30.

Here's the vacuum pump from the project truck

First thing to do is soak the screws down with some penetrating oil. Even after letting them sit for 30 minutes, some of them were tough to get out.

Now to remove the cover plate from the one way valves. You can also see there was quite a bit of oil build up. Not sure if that's normal or not. Make sure to keep track of all the parts the come out. Those two little springs could roll under something...

Remove the rubber seal from the back of the plate that was just removed.

Put the new seal in the plate.

New we can pull the one way valves and their seals from the vacuum pump. I used a 90 degree pick tool to do this. I don't know if you could use a magnet as they valves were stuck to the seals pretty well.

Now pull the valve seals. Again, I used a 90 degree pick tool to pull them out.

Since the main plate screws have been soaking for a while with penetrating oil (you did remember to do that, right?), they should be ready to remove. Remove the screws from the diaphram housing now. Once they are all removed, the main diaphram housing plate can be removed. This could take some doing. I ended up having to hammer a putty knife between the two halves to get the top plate off. You could use a chisel or the flat blade screwdriver. I used the putty knife because I didn't want to risk breaking the vacuum pump housing. Here you can see the tear in the diaphram...no wonder the brakes weren't working

Remove the nut that holds the diaphram to the pump shaft using a 10mm nut driver or socket. Note how the retaining plates are oriented before removing them. They should be re-installed the same way they came out.

About half way done now...here's the vacuum pump with the diaphram removed.

Now we can cleanup the parts. I cleaned the diaphram retaining plates and the diaphram housing plate with a wire brush and some Simple Green.

My repair kits didn't have the seal for the top plate (which was kind of strange) but there really isn't a reason to open it unless the pump is completely inoperable. Here's a pic of the pump with the top plate removed. You can turn the bottom gear and see how everything works.

The vacuum pump can now be re-assembled with the new parts. PUt the top plate back on (if you removed it...and be sure to put the new seal in)

Assemble the diaphram retaining plates and attach the parts to the vacuum pump shaft. Make sure when tightening the nut down that the holes in the diaphram line up with the housing.

Re-install the diaphram housing plate now. Make sure you get the orientation right. As you can see in this pic, I didn't bother to put it back in the right orientation. The smaller of the two barbed fittings should be facing at 12 o'clock (pointing straight up AWAY from the bottom gear). The larger barbed fitting should be facing about 8 o'clock.

I used anti-sieze paste on all the screws. Just wanted to make sure this was a little easier if I ever have to do it again.

Install the valve seals and one way valves now. I installed them in the same orientation that I removed them.

The valve in the larger barbed fitting chamber should be facing 'UP'. That means the metal part should be facing up.

The valve in the smaller barbed fitting chamber should be facing 'DOWN'. That means the metal part should be facing into the vacuum pump housing.

Almost done...

Now put the springs back onto the valves.

Install the cover plate with the new seal that was installed earlier. You can see here that I moved the diaphram housing plate to the correct orientation.

And it's done!

Give the bottom gear a few spins. Notice it's a little harder to move it now...and it makes some interesting noises now. Kind of sounds like a strange diesel duck call.

Follow the shop manual on re-installation into the car. It's probably just, "Install is reverse of removal" Which we all love SOOOO much.

At this point, I also replaced the hose from the block to the vacuum pump. I had some silicone heater hose sitting around so I decided to replace the old beat up one that was on the truck.

Time from start to finish:
For a beginner with proper tools, I'd say 1.5 hours. That should include the time of removing the vacuum pump, R & R of all new parts and installing it back in the car.
Cost of parts:
About $30

Back to Projects...

Club Updates:

01-14-2006
16v CIS-E, Converting to Megasquirt

03-22-2005
Rebuilding Steering Rack

03-06-2005
Axle rebuild

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