I just had one let go ,the bearings fell out of the housing giving the assembly a nice wear mark .The tick ,tick ,tick noise gave me concern that I had a lower bearing issue .The pump was actually still performing well up until last startup on friday when I noticed no vacuum during braking.Im now concerned about the 12 tiny bearings that have scattered amongst the engine,the pan will come off next weekend , 400K plus and pump looks orig.
On another note Ive owned some 190d cars and had much more issue with these vac pumps vs the 617 s .An example of durability concern was with the armature fingers ,weak spot and would break at this point.

Progress
 

I got the cam installed, timing chain crimped, and the oil pump bolted up. I got the head bolts, pan gasket, and other parts yesterday, so I will probably get the engine ready to run today with the exception of the vac pump (it has not arrived yet). I pulled the injection pump the other day, and will install and time it today, now that I have th gasket.

New chain crimped

New cam installed

Almost finished!
 

I had a couple hours available to work on the car today. I got it almost ready to start. I removed the motor mount arm to get the oil cooler hoses out, to replace them. The upper hos was available new, so I had to make a new lower hose using the old metal tubes, and replaced the rubber hose. I went to my local A/C shop and bought some #12 hose and some sleeves. I have a crimper, so I cut the hose to the proper length, and crimped it on. It turned out great.

I got both hoses installed, wow it is so easy with the arm and the injection pump removed!

Photo of both hoses. I also got the IP timed and the rest of the fuel system hooked up. All I have left to do is the rocker arms, oil pan, and vacuum pump (it has not arrived yet).

Just as a note for the DIY crowd ,Ive pulled several vac pumps over the yrs and it always pays to be patient with these allen headed bolts that are used on this unit.I eventually came to the understanding that pulling the radiator is the only sure fire bet to get easy access to these bolts.The oil and grim at this location is usually also very high so a trip to the car wash and to scrap out each bolt before getting a tool is a good idea.The last excerise in not having a stripped alllen bolt at the begiinning of this project is to use a socket allen wrench tool ,once youve got it in the bolt hit it with a hammer to make sure its set, an extension makes this easier to accomplish.Happy DIY EN.

Such a beautiful thing!
 

The vacuum pump arrived today, and it is nice! It was purchased from the Classic Center. I think by tomorrow afternoon, the car will be running. Woo-Hoo!

I found the vac pump cam to be bad, and that is what might have caused the pump to fail. It has divots in the surface where the roller has dug in. It is getting replaced with a good one. First photo is the bad one, the second is the good one.

THANX Rich for this informative thread chock full of good photos .

So I finally relented and ordered a new vacuum pump to replace the original in my 1983 300TD with 215,000 miles on it, even though I inspected it last year and did not see any signs of impending doom--the bearing looked fine as did the cam drive surface. But too many tales of woe and I spent money having the head rebuilt a few years ago and would hate to see that go away.

In looking for a new pump, I found one site that had a warning about installing the new pump, that it required a professional mechanic, without identifying any potential pitfalls. I have had mine off a few times and other than rotating the drive cam so the bearing mates with a low spot, inspecting the cam drive surface and replacing the gasket with a new one from MB, I am not sure what other pitfalls may exist. Can anyone offer any other advice?

Peter

Hell ide rather take the jeep trails up the side of the mountain for adventure!!

If you have had your pump off and on a few times you will not have a problem. A lot of people do it by simply removing the power steering pump belt, however, as Rich said, removing the power steering pump itself provides better access to the vac pump.

One step forward, two steps back
 

After installing the vac pump, I decided to adjust the valves (one of the last things to do before firing it up). I got #1&2 done, and was turning the crank to adjust #4, and it bound up tight. I assumed there was a piece of metal stuck on the crank gear. I also noticed that the chain was riding off the side of the upper guide rail, and it looked bent. While I was waiting for another guide rail to arrive, I pulled the crank pulleys so I could get to the guide rail pin. I removed the rail, and shined a light down the cavity. I saw a piece of metal stuck between the two rows of teeth on the crank gear, so I knew I found the problem with the bound up chain. I was able to get a magnet placed right next to the offending metal piece, and used the sharp end of a long rat tail file to dislodge the metal from the gear. It stuck to the magnet, and I was able to remove it without loosing it. I am sure it was a piece of the vac pump arm. Photo below. I will be getting the rail tomorrow. I will have to assemble a few more things now, but it is a small price to pay for actually being able to retrieve the metal shard....Rich