Originally Posted by Mark DiSilvestro

I wouldn't get a used pump unless there was proof it had been very recently installed, or it was very cheap and I had no other choice.

A few years ago, I had the vacuum pump fail on my '84 Euro 300TD at the end of a 200-mile trip to Virginia Beach. Fortunately, the bearing balls managed to find their way to the oil-pan without wrecking the engine. I found a working used pump at the local Pick-N-Pull off an '80 240D for $20. That pump was working perfectly and the bearings were still solid, so it got my TD up and running again. But then I started thinking, how long did I want to trust a used vacuum-pump off a car even older than mine. So I decided to look for a new bearing-kit or pump that I could install before my 200-mile return trip to Alexandria.

First, I found a lever & bearing kit at a local Import parts store for about $270 (About the same price as PeachParts) But when I went to install it, I discovered my original pump also had a broken piston, which was NLA. I wound up buying a new pump for $300 from a friend of a friend that had a small indy Virginia Beach Mercedes repair-shop.
Later, I used that new lever & bearing kit to rebuild the $20 used pump to install on my '82 240D.

The main problem with these pumps is they originally used a plastic cage inside the bearings to secure the balls. After many years, the plastic cage disintegrates and the balls fall out. When that happens, you still have a fair chance that they may work their way through the timing chain to the oil-pan without catastrophic engine damage. But then what happens if you continue to drive the car, is the lever is now hammering against the drive-cam of the injection pump. That's what probably broke my vacuum-pump piston. Eventually, the lever shatters and those fragments will tear up the timing chain. I was lucky that my pump failed near the end of my trip, as I never heard it, and only discovered a problem when I went to use the brakes a few miles before I arrived and found I had lost my brake power-assist. When I finally tried to shut off the engine, and it wouldn't, that sort-of confirmed there was a problem with the pump.

Incidentally, the new lever & bearing kit had a plastic cage bearing, but I went ahead and installed it in my 240D pump anyway, as I expect it will take many years for it to fail.
OTOH, the new pump that went in my TD had a steel bearing cage.
Both parts were new OE Pierburg manufactured.

There have been some threads here about just replacing the lever-bearings with some generic off-the-shelf items. But they included a lot of discussion about trying to find the right design and quality of replacement bearing. As I didn't have the equipment to extract and install bearings, and my TD's pump-lever had already been damaged by hitting the drive-cam. that wasn't an option for me anyway.

Happy Motoring, Mark