The EGR valve is vacuum switched and there is a gasket to seal it to the intake. It's unlikely that a leaking gasket would admit enough air to unbalance the system sufficiently to throw codes and disrupt proper operation of the car. If the EGR valve is not working properly it will cause the computer that runs the system to set a code.

You can remove the EGR valve and test it by applying a vacuum with a Mityvac or similar vacuum pump. You should be able to see the valve move in and out when you apply/remove vacuum. The electrical connection on the EGR valve tells the computer that the EGR valve is still there and working. You can test the electrical connections with your meter by looking for continuity between the pins and then pushing the valve open by hand (it's spring loaded). All you need to see is that the meter changes when the valve is opened and closed - this shows that the switch inside the EGR valve is switching. I don't know which pins, you will have to experiment. I think there are three wires on my 606 EGR but it is an NA engine and I am leery of assuming it is the same as yours.

If the EGR valve does not work with vacuum (broken vacuum diaphragm inside or crudded up with exhaust/oil) or if the electrical switch does not work, the computer will not be happy.

Hint: It's been my experience that the code set by the computer does not always point to the right part of the system.

Jeremy

__________________

"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970

Just a slight correction, there are no electrical connections on the EGR of the 606.962. The ECU verifies correct operation by measuring air flow characteristics through the MAF rather than via an electrical contact.

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-Evan


Benz Fleet:
1968 UNIMOG 404.114
1998 E300
2008 E63


Non-Benz Fleet:
1992 Aerostar
1993 MR2
2000 F250

When I took my intake manifold off the first time (I don't recall the mileage but it was around 75k miles) to venture into a glow plug replacement using Lightman's procedure, I found a seriously clogged intake manifold with a very dirty underside - big black stain that looked like a spray pattern. So, I took the EGR valve off and found the gasket was folded over at one corner so that about a third of the gasket between three bolt holes was on the inside, in the air flow path. The point is, air didn't leak in there, it shot out and carried the goo on the inside with it. I do not believe the area spends much time under vacuum, so the stuff is leaking out not in.

Don't underestimate the ability of a clogged intake manifold to make the sensors send the computer bad readings. While that did not happen with mine, the performance improved drastically after I cleaned the manifold out. Others have noted they did this with solvents and so on - mine was seriously clogged and I ended up using a high pressure spray wand at a do it yourself car wash bay after soaking it for 24 hours in a sequence of Diesel fuel and commercial sovents/degreasers which softened the stuff but would not remove it. The high pressure spray wand made short work of the stuff and a huge mess in the bay that I had to clean up with another $2.50 of quarters.....

Jim

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Own:
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles

Owned:
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)

Now that I think about it. When I remounted the IM last time I had difficulty getting it seated in the intake pipe. Could a poor connection there cause this?

__________________

Muleears
'07 E320 Bluetec 133K my DD
'04 Jaguar XJ8 VDP, 34K
'10 Hyundai Accent 60K Grocery Getter
'02 VW Golf soon to be on the road again
'97 E300 Diesel Son's DD
'61 VERY tolerant wife

Hampton Roads, VA USA

Gone but not forgotten:
'67 250S 95K
'86 300SDL
'87 300D Turbo, 364K! R.I.P.
'98 E300 Turbodiesel, 213K
'02 S420, 164K
'01 Prius 138K