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  #1  
Old 06-26-2007, 04:31 PM
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81 300CD vacuum line question.

So, theres a black vacuum line that runs through the firewall, it connects to the Y connector at the VCV, but currently isn't connected to anything inside the car! I found this on like day 2 of owning the car (its been about 5 months now). I plugged it up, because it is def getting some vacuum. So my interest in finding where it goes was resparked when I was helping my friend with his 84 240d and noticed his wasnt hooked up to anything either! His is much shorter than mine (only about 8 inches show through firewall inside car where mine is about 2 ft).

Anyway, I had originally thought this would have something to do with my ACC, but I pulled the dash all apart one day and, as far as I could tell, everything was in place. Its a total plate of spaghetti back there, so kinda hard to tell. My friends car doesnt have ACC so, I am gonna rule that one out anyway. Any ideas? As I said, its the BLACK one. Thanks in advance for your responses!

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1981 300CD 260k w 60k on new motor
1983 240D 4spd Manual
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  #2  
Old 06-26-2007, 04:34 PM
Abandon the Roads!
 
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Location: Texas
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The black line that comes through the firewall into the driver's kick panel area on a 123 is a vacuum vent line, meaning that it lets vacuum off to protect your components.
It basically allows air into the system to keep the vacuum at 15 PSI. I would advise that you unplug yours to protect your vacuum pump and vacuum diaphragms. They can survive more than 15 PSI, but it will cause damage over time.
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  #3  
Old 06-26-2007, 04:39 PM
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Wow, well, that would explain why they were both disconnected! Thanks man, I'll unplug it immediately.
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1981 300CD 260k w 60k on new motor
1983 240D 4spd Manual
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  #4  
Old 06-26-2007, 04:49 PM
Abandon the Roads!
 
Join Date: Feb 2007
Location: Texas
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I actually wondered about that too. My brother wondered about it when he had the car, and my dad wondered about it too. Fortunately my dad didn't want to mess with it because he mostly worries about his car, and my brother basically didn't touch anything not involved in driving for the three years he had the car. He would notice that the A/C was dying, the radio was shot, and all sorts of vacuum problems, but he never did anything.

Then I looked it up. I swear, Mercedes should have put a label on those things. People wonder about them, and it's really hard to guess their purpose.
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1984 300DT turbo 138k mi

Still hauling me to school and back.

Handy Site:
http://www.dieselgiant.com/
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  #5  
Old 06-26-2007, 04:55 PM
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Yeah... I mean, the way it just hangs behind the dash sure makes it look like it should go to something. Thanks again for your help. Its been unplugged.
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1981 300CD 260k w 60k on new motor
1983 240D 4spd Manual
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  #6  
Old 06-26-2007, 06:29 PM
Craig
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Quote:
Originally Posted by mistergood View Post
Yeah... I mean, the way it just hangs behind the dash sure makes it look like it should go to something. Thanks again for your help. Its been unplugged.
Mine has a label under the hood that indicates it's a vent.

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