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  #1  
Old 06-26-2002, 06:33 PM
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Vac. hose identity

Found a stray vacuum hose under the dash yesterday.
Its black, and goes out into the engine compartment and connects to a "T" One side of the T goes into the white plastic thing at the end of hte fuel pump (ALDA?) the other hose continues up to the throttle linkage valves on top of the valve cover. Any idea where this belongs?

Also, can someone explain (briefly!) how oil gets into the vac. lines? I dont understand how a vacuum which should suck could do the reverse and pump oil through the system.

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  #2  
Old 06-26-2002, 06:55 PM
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probably the vent line

I think the blank line is a vent line, sort of like a ground. I am pretty sure I read that on one of the other posts around here.

With regard to sucking oil through the vac system, I think that often the vacuum fuel shutoff will leak at the IP (which has motor oil circulating within). When that diaphram fails, oil can get sucked back toward the source of the vacuum. There are probably other ways to accomplish the same thing.

later
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  #3  
Old 06-26-2002, 07:16 PM
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The black line is the vent for the tranny control -- it doesn't attach to anything under the dash, it is there rather than the engine compartment to keep dirt out of the vacuum system.

Oil gets in the vac lines from (usually) at leaking vacuum pump. When you shut the engine off, the vacuum in the lines will suck oil up, and eventually drag it all over the place. Very bad for the rubber bits, usually makes the sticky and soft. Oil can also get pulled in the shutoff, and once in the main line, everywhere else, too.

You can also get brake fluid in the brake booster, but I'm not sure that will migrate into the main vacuum system so easily -- would have to be quite a bit in there!

Peter
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  #4  
Old 06-26-2002, 08:44 PM
MVK MVK is offline
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Hi Walknight;
The black line you are talking about is a vent line its in the clean dustfree area for venting. This way no dust will get in sysytem tru that line. Its almost every one's nightmare to open the kick panel and not notice this line at once, but you get to see that line after working on other things and it scares you to death when you dont know if you knocked it loose. Let it be there in such a way that nothing will block it. If its really loose tie it ti steering column nusing with a tie. You can find this line in MB disk under the topic Engine then subtopic fuel infection system then sub-category "checking vacuum shut off for leak". Its on the 3rd or 4th page of this pdf file.

MVK
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Last edited by MVK; 06-26-2002 at 08:49 PM.
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  #5  
Old 06-28-2002, 07:47 PM
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So, what you are saying is, then, that I should take the screw out of it immediately!
This would explain the strange shifting action.

Thanks for the vac. oil solution too. I was sort of thinking that that could be the only explanation. Makes sense. Now to go change the gasket...
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  #6  
Old 06-28-2002, 11:51 PM
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Wallknight,

Where do you see evidence of engine oil in the vacuum system? If it is at the back of the "ignition" or starting switch operated by the key, I think you may have a bad vacuum diaphagm in the shutoff mechanism on the injection pump. That requires a new mechanism as I do not think a gasket solves the problem. In my experience with vacuum pump diaphragm leaks is they become visually apparent as the line going from the pump to the air intake gets black (it is a translucent white when new) and when the leakage gets bad you will notice heavy smoking at idle. NOt sure if your car has the vacuum line from the pump to the air intake or not, but it is there on 240D's and earlier models. Good luck, Jim
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  #7  
Old 07-01-2002, 01:41 PM
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Jim,
the oil is primarily between the ignition switch (dripping) and the port on the back of hte fuel pump. Some has also worked its way out to the splitter in the engine compartment that looks like Neptunes Trident.
I'm fairly sure that the vac. pump gasket is shot; pieces of it are hanging in clear view. However, there is very little oil in the rest of the lines.
So, how does one replace that mechanism?
Thank you,
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  #8  
Old 07-01-2002, 01:42 PM
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oh, almost forgot. When cleaning the hoses, I noticed that the port on the mechanism was a pool of oil that I couldnt clean out.

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