My Vacuum Pump has failed.
 

My DD is a '82 CDTD of a documented 104K -Maybe.
I have driven this car for about 10 years.
A few days ago I heard a new sound Chirping and clinking. I surmised the
sound was the A/C clutch..Wrong.. The trans began to shift oddly,sometimes
early, sometimes softly, sooner then later.

The sound became more noticeable. I checked the Vac. It was all over the place. 21, then nothing, then 15. My handy listening stick identified the pump as the perp.

Pulled the pump. It had lost a few bearings.

Ordered a new pump from Pelican (The expensive one) It's from SPAIN. Does anyone have experience with this item?

Jake12tech wrote of this failure. Priming the new pump was mentioned.
How do you prime this pump? I don't want to damage the new LITTLE balls,uncovered as they are. I had asked about the enclosed bearing pump
when I ordered it..no luck.

Can some forum member answer the priming question? and give me some
confidence in this manufacturer? Sounds URO to me. Carbureibar. S.A.

Thank you to the forum members. Any assistance is gratfully accepted

Your car has a diaphraghm pump. Consult the FSM to be sure, but I don't think it requires priming.

What does the face of the timer look like.

May not have been the cause of your problem but something to check before an new pump is installed.

Vacuum Pump Failure with pic of worn Intermediate (timer) shaft bushing
http://www.peachparts.com/shopforum/diesel-discussion/355899-vacuum-pump-failure-picking-up-pieces.html

second vacuum pump, help! on a trip-Toronto - PeachParts Mercedes ShopForum

New Vacuum Pump diaphragm ripped due to over tightened Nut. Bolt
Vacuum Pump Fails Again! - Mercedes-Benz Forum

Use zinc chromate.

I don't know how different your VP is from mine, but when I did mine a couple of months ago, the instructions said to leave the vacuum lines disconnected, start the car, add a little oil through the vacuum fittings, then reconnect the lines. This was for a Pierburg OEM pump (although I believe the OE part is just a rebranded Pierburg).

I asked around a little bit about this particular procedure, and it seemed like most people didn't bother. Personally, I felt like I wouldn't be able to deliver a significant enough quantity of oil through the narrow vacuum fitting rapidly enough to make any tangible difference, at least not before the regular oil supply took over. I guess you cold bather the engine side in a little bit of oil and accomplish the same thing, although the part seemed well oiled with assembly lube.

One would think it would be the roller/bearing that needes to be pre oiled and the rest of that articulating arm.

Yours ISN'T a diaphragm pump.

Neither is an '82 300CD.