Thanks Brian. Since my previous post, the cel has come on again. The valve is working so I guess it is the sensor on the top that is out. Looks like either way, I will have to buy a new egr, even if I block off the intake. Thanks, I will surf the 210 owners. Harvey

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hlg

Myself I'd think removing the control box would be one of the perks of removing the EGR valve. What'd be nice is if the cruise bracket were on something else then nearly that whole bracket would be gone as well.

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Jeff M.
Mercedes W123 DIY pages are now located here.
1983 / 1984 300D Sold
2000 CLK430 Cabriolet ~58k Sold
2005 Avalanche 4x4 ~66k

Jeff,

Are you speaking of the black box on the top of the valve cover on the 617? I was not aware that this could be removed because it had some type of vacuum control valve for the transmission in it? Is this correct?

Yes it has a black cover to the vacuum switches. No I don't believe it has anything to do with the tranmission, that valve is on top of the IP. If anything it'll help your tranny get a better vacuum source and lead to softer shifting since the EGR isn't wasting vacuum. It seems like most of those switches leak.

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Jeff M.
Mercedes W123 DIY pages are now located here.
1983 / 1984 300D Sold
2000 CLK430 Cabriolet ~58k Sold
2005 Avalanche 4x4 ~66k

Well, what are those switches doing if they are not trans related? I did not think that they were EGR related.

BoostnBenz is right - the changeover valve setups leak. On my 300SD, they leaked so much that the transmission had NO vacuum to soften the shifts. I disconnected the EGR and the changeover at the source and got back the vacuum.

I have read that they do effect the transmission by allowing the most vacuum to the trans (by shutting off the EGR) during off-throttle upshifts. But if they are disconnected, maximun vacuum will be supplied anyway.

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1984 300Sd 210k

Former cars:
1984 300D 445k (!!) (Strider) Original (and not rebuilt) engine and transmission. Currently running on V80 ( 80% vegetable oil, 20% petroleum products). Actually not, taking a WVO break.
1993 300d 2.5 275k. Current 120/day commuter
1981 300SD 188k (Hans) Killed by a deer

Those valves are what "tell" the EGR when to function, so if you are at 2/3 or more (for instance) then the EGR valve will be open due to the switches sending vacuum. I've owned 2 W123s, both had leaky EGR control switches, I ended up replacing it with a used one which leaked almost nothing.

Sure shifting will change a little to the softer as it takes a variable out of the source, with the EGR control box or it being fed vacuum all the of the vacuum from the pump being made will be available to the bleeder on the IP rather than getting lost at a vacuum leak on the camshaft cover.

__________________
Jeff M.
Mercedes W123 DIY pages are now located here.
1983 / 1984 300D Sold
2000 CLK430 Cabriolet ~58k Sold
2005 Avalanche 4x4 ~66k

So, those switches are only controlling EGR? And when they leak, they affect transmission shifts? Several forum members have replaced these switches to improve the shifts and eliminate the leak. However, they could have just as easily removed the switches altogether?

And, if there is more vacuum to the trans. after removing the switches, this can be adjusted on the trans vacuum valve on the I.P.?

Correct?

And, if I remember correctly, there are three plastic hoses going into the black box. One is vacuum supply. One is EGR output. What is the third? I seem to remember the third plastic hose heading back toward the IP for something. Could this be the modulation line that controls the function of the switch?

Yes.

In theory yes, but most of those valves don't adjust properly due to age and wear. Mine for instance bleeds to much air off and doesn't have the same response curve it should, so by increasing the vacuum it makes shifts better but I could still use a new valve.

Source, to EGR, vent. Remember if there wasn't a common (black) vent line then the vacuum pump could pull in an dirt or whatever into the system so it all gets it from a common vent line. The switches are just a controlled bleed, but occasionaly beomce uncontrolled leaks.

__________________
Jeff M.
Mercedes W123 DIY pages are now located here.
1983 / 1984 300D Sold
2000 CLK430 Cabriolet ~58k Sold
2005 Avalanche 4x4 ~66k

Brian, I think that one that goes back to the IP just connects to the vent line (the same one that vents the transmission modulator on the IP).

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'81 300TD Wagon 355k (Miss Diesel)
'83 300SD 180k
'84 500SEL 190k (Parting it out)

No that is an exception to the black line rule. That is vacuum going to the modulator but yes it shares the same vent line as the IP's bleeder valve.

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Jeff M.
Mercedes W123 DIY pages are now located here.
1983 / 1984 300D Sold
2000 CLK430 Cabriolet ~58k Sold
2005 Avalanche 4x4 ~66k

Well then, it appears that the black box and associated switches and all plumbing can then disappear . One cap on the supply to the box and one cap on the vent that returns from the box and the engine compartment will get about 5 pounds lighter

If it were me doing it I'd forget any caps and just replace the Ys with straight fittings or new plastic line. One less place for the rubber fitting to leak.

__________________
Jeff M.
Mercedes W123 DIY pages are now located here.
1983 / 1984 300D Sold
2000 CLK430 Cabriolet ~58k Sold
2005 Avalanche 4x4 ~66k

A good idea.

Also, does this common vent line have a common air filter somewhere on the vehicle that is the terminus of the vent line?

I presume so but I don't know where it is. I know it runs inside the cabin, but from there on out I'm not certain.

__________________
Jeff M.
Mercedes W123 DIY pages are now located here.
1983 / 1984 300D Sold
2000 CLK430 Cabriolet ~58k Sold
2005 Avalanche 4x4 ~66k