OK - so what does the EGR valve do to lessen the polluting characteristics of the 300SD? Did it reduce smoke or some other kind of pollutant? If so, maybe I am doing the right thing leaving everything hooked up.

It reduces NOx

__________________
1979 240D- 316K miles - VGT Turbo, Intercooler, Stick Shift, Many Other Mods - Daily Driver

1982 300SD - 232K miles - Wife's Daily Driver

1986 560SL - Wife's red speed machine

I've chosen to leave the EGR hooked up on my 190D. The car runs fine, and I'd rather have less NOx in the air we all breathe. Just trying to do my part, or I should say, not avoiding doing my part.

__________________
1987 W201 190D

Nitrous oxide? NO2? Not sure.

Which is worse:

Keep the EGR and reduce emissions.
And later release all kinds of crap when you have your manifold chemically & thermally cleaned to remove the EGR junk

or

Slight emissions increase, along with power and mileage.

__________________
$60 OM617 Blank Exhaust Flanges
$110 OM606 Blank Exhaust Flanges
No merc at the moment

MB knew their engines ran better without and EGR. Thats why they didn't install one until restrictive emissions limits forced them to choke the engine with it in 1981. The USA is the only country to get engines with a useless EGR, Europe and the rest of the world never had it.

Oxides of Nitrogen.

I'm in the camp of making the car run as well and efficiently as possible.
That means my EGR is disabled. For me, it was a simple removal of one vacuum tee. Personally, I believe that the car runs better and smoother, so as a result I am using less fuel, hence less emissions. Seems like a "green" choice to me.
I did leave all the 3/2 and EGR stuff on there, just in case my state decides it wants to start doing emission tests on old diesels.

If it makes you feel good, leave your EGR on and hooked up. But I`ll bet you, it isn`t working.
The EGR dumps exhaust back into the intake manifold, and the soot mixed with engine oil vapors from the intake manifold will sloowly coat the manifold with a nice protective coating of gunk. A sticky black goo that will cut down on air flow.

I have removed a number of them off of PNP W123 & W126 617 engines. Everyone I removed, the hole in the manifold was plugged tight with this stuff. Not sticky goo, but hard packed.

I removed the manifold off my 85, along with the other Calif. choking devices, and the manifold had 3/4 inch of black goo inside, along with an inop EGR. My milage picked up from 24 to 26 - 28MPG or so. It was a dog at higher elevations, and with the removal of stuff, that increased also. I use to be as slow as a 240D . .

I made the mistake of using a steam cleaner to blow the crap out of the intake, and had black stuff all over me .

Charlie

__________________
there were three HP ratings on the OM616...

1) Not much power
2) Even less power
3) Not nearly enough power!! 240D w/auto

Anyone that thinks a 240D is slow drives too fast.

80 240D Naturally Exasperated, 4-Spd 388k DD 150mph spedo 3:58 Diff

We are advised to NOT judge ALL Muslims by the actions of a few lunatics, but we are encouraged to judge ALL gun owners by the actions of a few lunatics. Funny how that works

Ours have all been disconnected for a long time.

__________________
-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 118k - mine - (OC-123,800)
'17 Metris(VITO!) - 37k - wifes (OC-41k)
'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)