I was doing a vacuum check on a 300d turbo which I recently purchased and I found 2 lines that go into the firewall right behind the instrument panel that were loose and not connected to anything.

One of the lines starts from the vacuum transducer underneath the air cleaner and across the front of the engine and into the firewall. It is the thickest line of the six.

The second line goes from the side of the vacuum control unit and goes up into the firewall.

I have included pictures of the lines from the starting point to the end.

I cannot find anywhere at the end of the vacuum where to connect these two black lines. I am not sure if they are designed to hook into a gauge, or I am not seeing something. There is not a lot of room to look, so I thought I would ask if anyone knows the solution instead of removing more things.

Attached Thumbnails

       

The biggest black vacuum line is a 'vent'. It does not connect to anything inside the car. I never try to trace where it goes to under the hood. Others may know.

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Not MBZ nor A/C trained professional but a die-hard DIY and green engineer. Use the info at your own peril. Picked up 2 Infractions because of disagreements. NOW reversed.

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1 X 2006 CDI
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1 x 87 300TDT wagon
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The smaller black line is the bleed for the vacuum control valve, nothing connects to it.

I know that one of them is a vent line (the line connected to the unit on the side of the injection pump, your first picture). It is not supposed to connect to anything, it simply allows clean dry air to be drawn from the interior.

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Respectfully,
/s/
M. Dillon
'87 124.193 (300TD) "White Whale", ~392k miles, 3.5l IP fitted
'95 124.131 (E300) "Sapphire", 380k miles
'73 Balboa 20 "Sanctification"
Charleston SC

I just wanted to make sure that I wasn't missing anything. I have a good vacuum line diagram, but it does not show where the lines go in off the firewall.

Looking further into the vacuum line diagrams, looks like both are vent lines.

__________________
Respectfully,
/s/
M. Dillon
'87 124.193 (300TD) "White Whale", ~392k miles, 3.5l IP fitted
'95 124.131 (E300) "Sapphire", 380k miles
'73 Balboa 20 "Sanctification"
Charleston SC

The white one is for the rear headrest release.

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