1983 300CD

I replaced the external check valve a few weeks ago because the internal plastic piece and spring were missing. I didn't see the missing pieces inside so I just replaced the check valve. Then I was having intermittent vacuum loss, so I pulled the vacuum pump off the car. I disassembled the vacuum pump and found the missing pieces inside the little pocket behind the nipple where the external check valve screws in--not knowing the internal layout of the vacuum pump, I was worried that they had churned through the engine--yet another smart design from MB. I think these pieces were blocking the vacuum in certain instances, causing the intermittent vacuum loss I was experiencing.

Anyway, I completely cleaned out the vacuum pump while I had it off, which included cleaning out the oil inside/behind the piston. Now I need to reinstall and I'm not sure if I should prime it with oil or if the engine sends it oil once it is running.

Thoughts on if/how to prime the vacuum pump/piston before reinstalling?

Thanks.

No priming needed

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1983 300CD Turbodiesel

The instructions with a new vacuum pump clearly indicate to feed 50cc of engine oil into the main vacuum intake immediately upon starting the engine the first time.

The 617 may be different, but the Pierburg for the 603 had a card with large print in the box warning you about it. If the manufacturer says to prime it, I'll go with what they say.

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Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

This makes a lot more sense. I'd like to have some kind of lubricant in there to prevent metal on metal for even a few seconds.

Not metal on metal, except on the roller bearing and arm pivots. If the later 1-tube pump, the piston seal is a teflon-like ring (maybe kel-F?). Older 2-tube pumps have a rubber diaphragm. Either way, pre-lube is smart since it takes a while for engine oil splash to reach the pump.

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1984 & 1985 CA 300D's
1964 & 65 Mopar's - Valiant, Dart, Newport
1996 & 2002 Chrysler minivans

sorry for the bad info.

I should've said, I didn't prime when I reinstalled my vacuum pump.

and it worked out fine.

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1983 300CD Turbodiesel

Before installing the VP line up the humps of the 'roller coaster track' of the timing device "vertical" (bump the engine) that way the VP will be tight against the block making it easier to put in the screws. Be very careful putting in the lower screw, its easy to strip out.

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1985 Euro 240D 5 spd 140K
1979 240D 5 spd, 40K on engine rebuild
1994 Dodge/Cummins, 5 spd, 121K
1964 Allice Chalmers D15 tractor
2014 Kubota L3800 tractor
1964 VW bug

"Lifes too short to drive a boring car"

Thanks all. Got it reinstalled this evening but didn't get it to a point where I could restart the car. Will report back tomorrow.