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  #1  
Old 02-05-2005, 12:05 PM
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Question SDL EGR Removal question

I am in the process of removing the EGR from my SDL. It has been disabled for a while but I've decided that the useless chunk of metal is probably just adding weight and adversely affecting my fuel economy (Just put that in for any EPA Inspectors that might be reading ) so its coming off.

I have read that the two EGR Vacuum solenoids/relays/switches can cause leaks so is there any harm in bypassing them altogether ?
Do they perform any other function other than controlling the EGR valve.

Thanks
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1991 M-B 560SEL Arctic White/Grey 99,000 Miles
1987 M-B 300SDL Ivory/Palomino 229,000 Miles (sold but never forgotten)
2006 Volvo XC70 Blue/Beige
1987 Porsche 924S Black/Linen
1972 Porsche 911 Viper Green/Black
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  #2  
Old 02-05-2005, 12:17 PM
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On the '86 there is a small filter and some "apparatus" behind the passenger headlight that runs the EGR system. I removed all of this when the valve came out. You will find a large black line that heads into the passenger compartment. It's a bit bigger than the others (5mm maybe?). This is a vent line. It has a rubber connection near the firewall by the brake booster. You can separate it at this connection and remove the black line entirely. You don't need to plug the end going into the cabin.
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  #3  
Old 02-05-2005, 01:53 PM
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Thanks Brian.
It was that Black line that I was most concerned about. I thought it might be connected to something important in the cabin.
Why would it just vent into the cabin??
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  #4  
Old 02-05-2005, 03:25 PM
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Apparently, M/B thinks the air inside the cabin is cleaner than the air under the hood of a diesel.

I wonder why they might think that?

So, the vacuum pump gets air from inside the cabin rather than underhood air.
Maybe it lasts a bit longer?
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  #5  
Old 02-05-2005, 10:10 PM
Brandon314159
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But doesn't a vac pump PUSH air out into the atmosphere?

I thought about this one day, changing the vac pump filter. Then I was like...wait...
Yeah
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  #6  
Old 02-05-2005, 10:21 PM
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Quote:
Originally Posted by Brandon314159
But doesn't a vac pump PUSH air out into the atmosphere?
A vacuum pump draws air from the vehicle. The goal is to eliminate all air in the system, thereby creating a "vacuum".

It PULLS air from the vehicle.
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Old 02-05-2005, 10:26 PM
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Quote:
Originally Posted by Brian Carlton
A vacuum pump draws air from the vehicle. The goal is to eliminate all air in the system, thereby creating a "vacuum".

It PULLS air from the vehicle.
So the black line is like the atmosphere side of things for the ERG? If air gets let into the system (Ie...something useful is done), then this black tube supplies the air upon deactivation? (returning to atm pressure)
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Old 02-05-2005, 10:37 PM
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Quote:
Originally Posted by Brandon314159
So the black line is like the atmosphere side of things for the ERG? If air gets let into the system (Ie...something useful is done), then this black tube supplies the air upon deactivation? (returning to atm pressure)
That's it. All the air enters the black tube and heads for the vacuum pump where it is expelled.
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Old 02-05-2005, 10:39 PM
Brandon314159
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Quote:
Originally Posted by Brian Carlton
That's it. All the air enters the black tube and heads for the vacuum pump where it is expelled.
Gotcha. Thanks
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  #10  
Old 02-06-2005, 02:58 AM
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OK, now I'm really confused
If the Black line is the source of clean cabin air for the vacuum pump, wouldn't disconnecting it as you suggest cut off that air supply?
Am I reading this wrong?
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  #11  
Old 02-06-2005, 07:54 AM
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From the vacuum diagrams that we have posted here, that black line appears to be a atmospheric reference. Even though the system uses vacuum to actuate various valves, it still needs a reference pressure on the other side of diaphrams for this to work. The diaphrams have to move when they open and close.
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  #12  
Old 02-06-2005, 10:18 AM
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Quote:
Originally Posted by Dervman
OK, now I'm really confused
If the Black line is the source of clean cabin air for the vacuum pump, wouldn't disconnecting it as you suggest cut off that air supply?
Am I reading this wrong?
Nope, your are correct. But, that large black vacuum line is the vent line for the EGR system only (and possibly the ARV if you have it). There are other vents that lead into the cabin for other devices. If you look on the side of the vacuum control valve for the transmission (on the IP), there is another black vent line that leads into the cabin. Most every vacuum device needs some sort of vent line.

Just check it out on your vehicle first. The '86 doesn't use that large vacuum line to vent anything else (nothing is teed into it). If anything tees into the large line between the beginning point behind the right headlight and the point at which it heads into the cabin, then, you must keep the remaining portion (from the tee and into the cabin).
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  #13  
Old 02-06-2005, 11:43 AM
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Thanks for the clarification, it all makes sense now
The Black Line from the EGR system has no connections between the firewall and the EGR solenoids.

Is the Filter that was on this line near the EGR system present anywhere else in the system? Do they have to be replaced periodically?
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  #14  
Old 02-06-2005, 12:38 PM
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I had asked about the filter once before. Apparently there are no filters inside the cabin at the other ends of the vent lines, AFAIK.

I'm not sure if anyone has actually found the ends of these vent lines, however.
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