My vacuum pump died
 

Hey guys,

As I was driving down the road today in my 72 220D my brake pedal all of a sudden became very stiff. I lost all braking power.

First thought was loss of vacume at brake booster. Pulled over, popped the hood, and took a gander. I disconnect the vacume line to brake booster and felt for pull. While the engine was on, I felt almost no vacume pressure in the line.

So, whats next? Should I have my mechanic rebuild it? Should I rebuild it? Should I buy a new one? Can I get at this thing without lifting the motor off the mounts? What else is the vacume pump used for besides brake assist?

Thanks guys. Cassidy

Of course the reason it quit makes a lot of difference... but typically if it is just the rubber diaphram that developed a tear then you should be able to do a great rebuild on it yourself...But my only experience is on a 1980 240 .. so I can't say for sure on yours...Someone with specific knowledge will probably be awake tomorrow to help on this....

For general reading and pictures...
http://business.baylor.edu/Richard_Easley//autofaqs/Vacuum%20Pump/Rebuild_vac_pump.htm

the actual kit for mine:

Did the diaphram replacement a number of years ago on the '68 220D/8. It should be the same as yours. It was a breeze, other than it is best approached from under the car. If you have a nice driveway or something dry to lie on, it should not take very long. Did you notice a huge black cloud out the back as the car burned lots of engine oil? That was my clue to what was going on in the first place. Luckily someone had told me what to expect when this failure occurred.

Yes!

I did notice tons of black/oil smoke. My car has a bad injector, so it already spits out a lot of grey unburned diesel fuel and fumes. When I saw the black I got more worried.

What does the vacume pump do to prevent burning oil?

And thanks everyone, I will order a kit and get to work!

It does not really do anything to prevent oil burning... it is just that if its diaphram is torn then oil can be sucked into the intake system and burned. So only its failure mode allows oil to be burned... not that the vacuum pump causes the engine not to burn oil.

Cazzzidy,

If you know your car has a bad injector why the Hell don't you get it fixed so you are not polluting the air more than you have to.

Now would be a good time to fix injector. You should get more mileage too.

As far as R&R the vacuum pump, it might be easier if you remove the radiator first.

P E H

Word
 

I havent fixed it yet because I got the car last week. I will fix it though this week.

I do feel really embarassed to drive in such a pulluting, stinky car. It is my daily driver though, so I needed to drive it.

I have plans to fix the vacume pump, replace motor mounts, clean the engine bay, change the front flex disc, valve cover gasket, and fix the injection problem all at once. Should be a nice weekend laundry list.

Cazzzidy
The photo Leathermang posted shows that membrane that fails. I have replaced one of those twice. The first time I just installed it and it failed a month later. Asked around and was advised to put several screws around the perimeter, and then tighten the center screw. That will keep the membrane from twisting as it is tightened. Still needs carefull attention or it will twist when the center screw is tightened and then it will tear right away. I recall it needed to be turned so a little so as to anticipate the twisting it would get when tightened. A little grease under the center plate helps.
Second one has lasted about nine years, so I guess I got it right.

When putting the diaphram back in... the plunger is supposed to be at a certain place.. you turn the engine to put it correctly... but I do not know what that place is....

Hadn't heard that. The plunger goes in and out. My guess would be that it is best to have the plunger about even with the outside edge.
If you look at Leathermang photo you can see how well the screw holes line up there. That is what you must get to or the membrane will tear again. Also note the center washer goes back in with one side facing out. I marked it with a color dot. Too easy to get that part reversed.

Just digging up a dead thread to gloat a bit.

Me and some buds used the vacume pump rebuild kit to fix an alleged torn rubber diaphragm. Well, when I got the front of the pump apart I discoverd that the plunger bolt had simply dethreaded itself and come loose. The diaphram was not able to push/pull correctly.

I put it all back together tightly, and it runs great. It was really easy. Took about an hour to take apart and rebuild the part. But dumb me forgot to lock-tite the plunger bolt into its thread. Will it fall out soon?

Cazzzidy


I rebuilt one last week and found it handy to clamp a "plate" across the back of the pump before opening it up. This will compress the springs and keep them that way while you replace the diaphragm. I wish I had read "Old Deis" comments before I did the job. I should open mine and reassemble it as per his suggestion.



.

My'79 300SD has a different type vacuum pump. It sort of looks like an 1/2 of an electric motor molded into the cover. It says "A. Pierberg" on the pump.

I have noticed times of low vacuum lately, I.E. hard brakes and longer engine shut off but the vacuum door locks work fine even days later after engine was run.

Is this vacuum pump rebuildable should I need to? Are kits available to rebuild it?

P E H

PEH
 

Checked Fastlane and a rebuild kit is available for your car. I have no experience with that pump, but my older one is pretty easy to rebuild.

Cazzzidy,

On my 300D the "plunger bolt" came loose and broke a hole through the housing. I had thought that it was a torn diaphram, but it wasn't. I replaced the diaphram since I had it apart, replaced the check valves and repaired the housing with JBWELD,,,,,,great stuff. No problems since.

I used Loctite blue to thread the "plunger bolt" back in and I hope it holds.

JCD