Vacuum pump diaphragm replacement pix - PeachParts Mercedes-Benz Forum

slarson80 · #1 09-13-2006, 01:46 AM

Here are some pix I took while replacing the diaphragm in my old type (two line) vacuum pump. This was in my formerly owned 79 300D. I removed the radiator, only because I had to anyway. It went to the radiator shop. I also pulled the condenser, I planned on doing that while the radiator was out. That's because the compressor is long gone and I have no plans on reviving the AC. Remove what ever you have to to give yourself enough room to work in there.

The instructions that came with the diaphragm rebuild kit said to remove the pump from the engine. That is not true with these old style diaphragm type pumps.

1) vacuum pump still on the engine with front plate & diaphragm removed. Basically what you do is remove the flat head screws that hold the front plate on. Do so in a cross pattern, not in a ring pattern. Then give it a pull and it will come off. Behind that there is a center bolt, it is a hex head, I forget the size. Undo that, then the center bolt, diaphragm, disks etc. pull straight out as one unit.

2) Front plate, removed, vac lines still attached. sitting up top, and out of the way. The check valves are in here. Behind the "diamond" shaped cover. I did not rebuild this part of the pump. Although there is a kit for it. From the symptoms I was describing to my indy parts desk (little bit of oil in vac lines. small pool of oil in air cleaner) I was advised that the diaphragm should do it. Note the black mark around the lower right screw hole, this is where the oil was seeping out. There wasn't really a tear but oil was getting around the diaphragm there.

3) Top view of pump. Keep in mind that the front plate and diaphragm are removed. Note radiator , fan shroud and PS belt are removed.

4) Diaphragm (removed) with center bolt and disks still attached. This is the front view or the side that faces the front of the car. Note that the smaller disk goes on this side, rounded edge toward the diaphragm. You'll want to clean up any oil in the front of the pump (rear of the front plate) also clean the front disk. Basically all the oil is supposed to be behind the diaphragm, only air/vacuum in front of it.

5) Rear side of the diaphragm, or the side that faces the engine. With disks still in place. Larger disk goes toward the engine, rounded edge to the diaphragm. The kit came with a new diaphragm. It also came with a new center bolt, a dab of blue loctite (for the new center bolt) and half of the screws (flathead) needed to replace them all. Go figure.

Hope this can help anyone who needs to rebuild a diaphragm vacuum pump!

Follow up: I've read that some people have had their new diaphragms fail. I think this is because they put the disks in backwards. Or overtighten the new center bolt. Be sure to put the rounded edge of the disks against the diaphragm itself. Mine is still holding up. (9/12/07)

nscarr · #2 01-24-2008, 06:57 PM

i was following the rebuild here and now a few months later the vacuum pump housing has broken where the diaphragm's center bolt lines up on the "front plate" where the check valves live. the bolt came free and it just punched a hole in the metal.

anyone have this happen? i'm guessing i was trying to make sure i didn't overtighten, but think it must have been loose and fell out, despite the loctite.

i'll have some pics later, but am trying to find out if a late (piston) style pump is compatible with my 1980 300D that has the early (diaphragm) pump. i have a pump from a 1979 300SD down in Oregon with the single-line out. otherwise i'll see about welding it up or buying a new one.

thanks for any help on this.
-noah

Stevo · #3 01-24-2008, 08:52 PM

Be sure to check the end play on the timing device while the vp is off. I had almost 2.5 MMs, which took out the vp. I dont know what its spoz too be, less than 1mm I would think.

nscarr · #4 01-24-2008, 09:41 PM

Quote:

Originally Posted by Stevo

Be sure to check the end play on the timing device while the vp is off. I had almost 2.5 MMs, which took out the vp. I dont know what its spoz too be, less than 1mm I would think.

thanks for the tip--how do i do it?

JimmyL · #5 01-24-2008, 10:21 PM

Threads with instructions are very valuable. Pics included are worth their weight in gold.
Pics in focus = priceless

nscarr · #6 01-24-2008, 10:59 PM

included below are my pictures from the original repair kit job. i have a few, so i anticipate multiple posts...
1) flat side of "bottom" disc
2) put rounded side of "bottom" disc facing diaphragm
3) rounded side "up"
4) diaphragm on
5) "top" disc on

nscarr · #7 01-24-2008, 11:01 PM

1) center bolt with copper washer on
2) front plate
3) umm... front plate again...
4) rubber check valve washers in
5) check valves in

nscarr · #8 01-24-2008, 11:04 PM

1) springs on
2) rubber gasket on valve plate
3) valve plate on
4) cam

Stevo · #9 01-24-2008, 11:07 PM

Quote:

Originally Posted by nscarr

thanks for the tip--how do i do it?

grab hold of the timing device and pull it in and out, it shouldn't move move more than a mm.

nscarr · #10 01-24-2008, 11:22 PM

here's what it looks like now:

pics below
1) new hole circled in red
2) new hole close-up
3) found the metal bit that blew off--back "in place"
4) view from bottom with metal bit "back in place"

so i may try to weld it back on before springing for a new pump--can't find a used one...

also need to check how the bolt will sit back in its spot... a little concerned about why it flew out in the first place; as mentioned above, i was worried about tightening it too much so may have left it too long.

slarson80 · #11 01-25-2008, 12:38 AM

Looking at this pic, it looks like you have the front / top / smaller disk backwards. Sharp edge against the diaphragm.

EDIT: It also looks like the diaphragm itself may be reversed. It should be the concave side facing the the engine and the convex side facing the front of the car.

nscarr · #12 01-25-2008, 12:42 AM

Quote:

Originally Posted by slarson80

Looking at this pic, it almost looks like you have the front / top / smaller disk backwards. Sharp edge against the diaphragm.

mmm... could be--the picture looks like it. unfortunately all of the parts came off with the bolt, so they just fell out. i remember being a little confused about which side was the more rounded side. i wonder if that caused some extra vibration to cause the center bolt to come out...

Zacharias · #13 08-19-2011, 03:52 PM

I am doing the vacuum pump diaphragm on my 1980 td this weekend. It has the old style, two-outlet pump.

I guess I am extra thick on some things, and obviously this job is going to be one of them. I am not getting the vulcan mind-meld with the postings I've seen on the job.

1. I read that I can do this easily with the pump in place, by just pulling off the front cover. Is this true?

2. Right now I have no vacuum to speak of, but no oil in the vent line either. Should I just go ahead and order the 'big' rebuild kit with the check valve pieces? (Note: I THOUGHT that was what I had bought until I got to the parts counter today. DOH. Should have known it was way too cheap....).

Thanks

nscarr · #14 08-22-2011, 01:03 PM

In my limited experience, the job can be done with the vacuum pump in the car--I found it easier to work with on the bench, especially since everything had fallen apart on me. But to take off the vacuum pump, I also had to remove the AC pump, which was in the way of the (stripped!!!) allen bolts on the vacuum pump.

I would order the big kit and replace everything. Good luck!

Doktor Bert · #15 08-22-2011, 03:04 PM

Nice write up and pics!!!!!!!