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  #1  
Old 09-30-2009, 03:40 PM
azitizz's Avatar
MB 1985 300TD Wagon
 
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Location: Winnipeg, Canada
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Where does this Vacuum line lead to?

Hi There, Im wondering if anyone can identify weather this vacuum line is meant to be attached somewhere? While trying to diagnose vacuum leakage on a 85 300TD I came across this hose that was completely disconnected inside the cab.
It comes out into the engine from under the drivers side firewall (picture 1) in the cab, and goes through the small air filter (picture 2) and splits off to two different electric switches (from what Im guessing they are) Its a beefier line than all the others. perhaps 7 or 7.5mm? or even 8mm? but the largest one I can see in teh whole vacuum system.

I know theres supposed to be one line (or maybe more?) that end up in the cabin to draw cleaner air from.

In an earlier thread Someone Identified annjother line as the one with this function already so Im wondering now if there are supposed to be 2 lines in the cabid sucking air onr only one? and if so which one is it? They are both Black lines. The other one is comming from the shotoff valve picture and description in this thread:
Where does this Vacuum line lead to?
The difference in the picture of the shotoff valve in mine is that it doesnt split off in a tee. It simly goes directly from the hose the hand is holding to the cab.
ANy Ideas???
Thanks

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Where does this Vacuum line lead to?-vacuum-pics-001.jpg   Where does this Vacuum line lead to?-vacuum-pics-002.jpg  
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Old 09-30-2009, 04:27 PM
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That's a vent, it just connects to "nothing" inside the cabin.

-Jason
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  #3  
Old 09-30-2009, 04:59 PM
azitizz's Avatar
MB 1985 300TD Wagon
 
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Quote:
Originally Posted by compu_85 View Post
That's a vent, it just connects to "nothing" inside the cabin.

-Jason
Good to know, Thank you. Do you know if is supposed to be the only one vented? or is there typically more than one like that?

Also Ive found another line that holds no vacuum. It goes from the round metal disc like part that connects to the shutoff valve all the way behind the engine and connects to a banjo bolt thats on what looks like the exhaust manifold (picture).

Should this hold a vacuum (going into the manifold?) and if not where does it lead and how can one find the leak if its not the banjo bolt itself?
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Where does this Vacuum line lead to?-vacuum-pics.jpg  
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Old 09-30-2009, 05:18 PM
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That line is supposed to go to a switchover (overboost protection) valve, located on the drivers side fire wall, then to that round disc (ALDA). I have it (CD) going straight to the ALDA, bypassing the switchover valve, I bought it that way and have left it alone.
The SD's is hooked up. I have not checked to see if it holds vacuum, but with the engine running there will be pressure.
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Old 09-30-2009, 05:35 PM
azitizz's Avatar
MB 1985 300TD Wagon
 
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Quote:
Originally Posted by toomany MBZ View Post
That line is supposed to go to a switchover (overboost protection) valve, located on the drivers side fire wall, then to that round disc (ALDA). I have it (CD) going straight to the ALDA, bypassing the switchover valve, I bought it that way and have left it alone.
The SD's is hooked up. I have not checked to see if it holds vacuum, but with the engine running there will be pressure.
You mean Positive pressure? (i.e. it would blow air out from the manifold into the line that goes to the ALDA?) In mine it also goes straight to the ALDA, reading a bit a can see thats what its called. However on the diagram here: http://home.comcast.net/~phantoms/vacuum/egr_california.jpg it seems to show it is supposed to lead to a "Switchover valve, boost preassure aneroid" then to a line that leads to the ALDA. Im wondering if my vacuum leakage is caused by teh lack of vacuum through the manifold.
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Old 09-30-2009, 05:46 PM
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Quote:
Originally Posted by azitizz View Post
Good to know, Thank you. Do you know if is supposed to be the only one vented? or is there typically more than one like that?

Also Ive found another line that holds no vacuum. It goes from the round metal disc like part that connects to the shutoff valve all the way behind the engine and connects to a banjo bolt thats on what looks like the exhaust manifold (picture).

Should this hold a vacuum (going into the manifold?) and if not where does it lead and how can one find the leak if its not the banjo bolt itself?
FYI. The 85 model has 2 vent lines into the cabin. One is filtered and one is not. The filtered line comes from the Emissions crap and the other comes from the IP.


Post #4 describes your picture.
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  #7  
Old 09-30-2009, 06:03 PM
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Pressure, positive pressure, vacuum, sorry must have left my engineering degree in my other suit. But it's coming off the intake, so...
Anyway, I did mention about the switchover valve, the pic shows it hooked up on the SD. Would that line eventually lead to the atmosphere, which would be why you can't get any vacuum?
There is only the one vent on my cars.
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Where does this Vacuum line lead to?-switchover-valve-circiled.jpg  
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  #8  
Old 09-30-2009, 06:22 PM
azitizz's Avatar
MB 1985 300TD Wagon
 
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Quote:
Originally Posted by toomany MBZ View Post
Pressure, positive pressure, vacuum, sorry must have left my engineering degree in my other suit. But it's coming off the intake, so...
Anyway, I did mention about the switchover valve, the pic shows it hooked up on the SD. Would that line eventually lead to the atmosphere, which would be why you can't get any vacuum?
There is only the one vent on my cars.
Thanks for the pic. I see mine actually does go into a switchover valve before going into the ALDA. My switchover valve looks much smaller but It seems like its connected the same way. There is slight vacuum coming from the line to the Manifold but not enough to register on a gauge, barely moves the needle. Could this be a source of the problem?
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Old 09-30-2009, 08:54 PM
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No, that is isolated from the rest of the vacuum system. Everything else is "powered" by the vac pump, you can see those two systems are separate.
That is of the SD, the one on the CD is smaller.
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Old 09-30-2009, 11:37 PM
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MB 1985 300TD Wagon
 
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Hmmmm, Ive replaced the rubber connectors on prety much every line to the various parts/valves/modulator and have fixed a leak in the transmission modulator by replacing the rubber cap. It now holds a nice vacuum.

Still though I cant turn the car off by the key. I was able to until I switched around the lines as they were set up somehow differently, but I have them set up just like the diagram above (link). Ive kept the door lock and climate controll system out of the loop thus far to try and find the problem, could they be linked? (climate/door locks and engine off?)

Is there a way to tell if the shutoff valve either in the ignition or near the IP are faulty? this is the only thing I can think of. Why else could I not shut it off by key turning?
A good pump of the vacuum gauge on the solid brown line that goes to the ignition switch through the firewall will stop the engine once the ignition is turned off and still running. Not sure what that means. It seems like it needs a hefty amount of vacuum to accomplish it though, although Im not sure, perhaps its normal. I'm able to also stop it simply sucking the line with my mouth.
Ive attached it directly to the brake booster line and plugged up everything else and it shuts off when you turn the key but it takes quite a while 8 or 9 seconds. And then theres starting issues with that setup.
Any help or advice is immensely appreciated.
Ive done so much work and learned so much so far from this forum. THANK YOU!
P.S. There is good Vacuum (20+hg) coming from the pump itself on the brake booster line so Im pretty sure its not the problem.

Last edited by azitizz; 09-30-2009 at 11:52 PM.
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Old 10-01-2009, 10:37 AM
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Okay, how did you take the climate/door locks out of the loop? Did you plug off the line going to them, or just unplug the yellow valve?
Check for oil in the brown line from the IP, my SD would shut off when I applied vacuum to it, but there was oil in the line, suggesting a failed shut off actuator, I replaced it, the engine now shuts off with the key.
The other thing I can think of is a faulty ignition switch vac shut off valve.
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Old 10-01-2009, 10:48 AM
azitizz's Avatar
MB 1985 300TD Wagon
 
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Quote:
Originally Posted by toomany MBZ View Post
Okay, how did you take the climate/door locks out of the loop? Did you plug off the line going to them, or just unplug the yellow valve?
Check for oil in the brown line from the IP, my SD would shut off when I applied vacuum to it, but there was oil in the line, suggesting a failed shut off actuator, I replaced it, the engine now shuts off with the key.
The other thing I can think of is a faulty ignition switch vac shut off valve.
I believe the doors and climate are out of the loop because theres 2 yellow lines coming from the firewall, going into a 3-way beige piece, and leads to a 4 way rubber connector that also has a green line coming from the firewall connected to it.
This 4-way connector isnt attached to any vacuum source from what I can see. I havent seen any oil or residue in the brown line and Ive taken it off and on several times.
Is there any way to test the two parts to see if they are faulty? (i.e. would vacuum be a reliable telltale sign?)
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Old 10-01-2009, 11:39 AM
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You have an '85 which is a bit different from mine, however the info provided is for your car. Yet this aspect should be the same.
The ignition switch valve (#14) has two lines going to it, one is from the main vac line, (#47) closest to the firewall. It seems you have that disconnected, (is this correct?) it's connected with the same distributor, (three way or four way rubber connector plugged into a yellow check valve) line as the climate (green) and lock system (yellow), so the ignition switch is also out of the loop.
#38 is from steering lock to IP (brown with violet stripe).
#47 is from steering lock to vac pump (brown).
They have to be hooked up, or the key won't shut off the engine.
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Where does this Vacuum line lead to?-ignition-vac-85-td-circled.jpg   Where does this Vacuum line lead to?-ignition-vac-85-td-002.jpg  
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Old 10-01-2009, 03:54 PM
azitizz's Avatar
MB 1985 300TD Wagon
 
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Quote:
Originally Posted by toomany MBZ View Post
You have an '85 which is a bit different from mine, however the info provided is for your car. Yet this aspect should be the same.
The ignition switch valve (#14) has two lines going to it, one is from the main vac line, (#47) closest to the firewall. It seems you have that disconnected, (is this correct?)
No, the brown line #47 coming from the ignition switch actually goes to a 4 way connector.(red dotted line) which splits 3 ways: The main vacuum line, to the Blue Flying sauce, and the 3rd to the EGR and Turbo (after passing through the various switches)

You can see the brown and blue line going into what I think is the shutoff valve? (drawn Blue dotted line) #38-brown with blue stripe.

So the brown line is connected to the 4 way which is directly plugged into the Main line, but still doesn't seem to be enough vacuum to shut it down when the key is turned. Ive plugged the brown line directly into the main line before and it will shut off the vehicle but it takes a long time and then it seems to be having starting problems.
I cant find a diagram where it indicates where the brown line should be plugged into. At the moment the green and yellow lines are sitting there connected to a 4-way plugged up on the other 2 open ends with golf tees.
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Where does this Vacuum line lead to?-vacuum-general.jpg  
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  #15  
Old 10-01-2009, 04:24 PM
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Okay, there is so much there I don't recognize or understand, sorry, can't help.

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