Today while looking under the hood for trouble. I found that the vacuum hard line from the pump to flex hose connector was loose. The fitting is right behind the steering pump filter if that helps you to visualize what I'm talking about. I wasn't having any problems with anything that runs on vacuum so I just tightened up the line.

But what I saw made me curious. The vacuum line goes directly back to the brake system firewall with no branches along the way. But I have vacuum lines around the engine, so I looked for their source. The lines all run back to what looks like a small electric vacuum pump in front of the right wheel well and behind the head light.

I don't think I've ever heard tell of an auxiliary vacuum pump. Was I asleep and missed this? It looks stock, but I can't find it in the service manual.

The plastic bracket that holds the little electric pump is broken and the pump is just sitting there in the wheel well. I'd like to fix and/or replace it but I'm at a loss as to where to go. Any help would be nice.

Attached Thumbnails

   

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Will W - 1984 300SD federal

w126 has a separate pump for the door locks. however it was my understanding that it is mounted in the trunk. maybe early w126 has the pump in the engine bay? or maybe someone moved it and thats why it is just sitting there.

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1981 NA 300D 310k miles

Pictures are essential in ID-ing what you've got and suggestions for fixing, as needed.

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Current Stable

• 380SL (diesel)
• Corvette C5
• Manx
• Baja Bug
• F350 Powerstroke
• Auburn Boattail Speedster replica

I don't know of any MB of that vintage with an electrically operated vacuum pump for engine auxiliaries. The 126 did have an auxiliary pump in the trunk for the door locks. The 123s of that era used manifold vacuum (gas) or engine driven vacuum pump (Diesel) for all engine controls (shutdown, EGR, transmission shifting control), door locks, and climate control flap actuation.

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The OM 642/722.9 powered family
Still going strong
2014 ML350 Bluetec (wife's DD)
2013 E350 Bluetec (my DD)

both my kids cars went to junkyard in 2023
2008 ML320 CDI (Older son’s DD) fatal transmission failure, water soaked/fried rear SAM, numerous other issues, just too far gone to save (165k miles)
2008 E320 Bluetec (Younger son's DD) injector failed open and diluted oil with diesel, spun main bearings (240k miles)

1998 E300DT sold to TimFreeh
1987 300TD sold to vstech

+1 on pictures...

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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

You want pictures? You get pictures :-)

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Will W - 1984 300SD federal

That is not a vacuum pump.

I believe it is the "vacuum converter" that signals the egr valve

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check the right wheel well in the trunk for the pump

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1981 NA 300D 310k miles