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Today I finally replaced the EGR valve on my 1998 Mercedes e320 Wagon, It was easier than I thought and only took this novice two hours.

This stock photo shows the top of the EGR valve assembly on the left and the bottom on the lower right. I also purchased a new metal gasket that goes between the EGR valve assembly and the engine block. Two years ago I replaced all three EGR breather hoses; two on the driver's side valve cover and one on the passenger side valve cover. I also pulled the covers and thoroughly cleaned them.
The hoses get hard and brittle. If they are original I suggest getting new ones.

The tools I used are:

3/8 drive ratchet 10mm socket with an angled adapter for the 10mm hex head bolt that holds the breather snorkel to the engine.
A 1/4 inch drive ratchet and E-10 Torx socket to remove the two bolts that secure the EGR pipe to the block.
A 3/8 drive ratchet with an E-12 Torx socket to remove the two bolts from the EGR valve assembly. A wobble socket would have worked better for the EGR valve assembly bolt near the valve cover.
A 24mm open end wrench to loosen the EGR tube nut and a 22 mm wrench to hold the nut below it.
A small screw driver for prying and a small hammer for tapping.

I found an excellent YouTube video that detailed the repair.

I credit the video for making the job so easy. A few comments that you may find helpful:

1) The EGR tube is a soft alloy, maybe aluminum and is fragile. It is important to unbolt the flange around the tube so you can move the tube out of the way when removing the EGR valve assembly. The tube does not come out of the engine block but will drop to one side when the flange is removed. I had to tap the flange with a small screwdriver to move it. It appears not to need any sealant. The tube has a crimped section which allows it to be safely bent when putting it back in the EGR valve assembly.

2) After I loosened the 24mm nut on the EGR valve assembly I could not get the tube to pull out of the assembly. I sprayed a little WD-40 in there and then carefully tapped the underside of the 24mm nut. That pushed up against the tube and gradually lifted it out. The tube has a ferrule on it which fits snugly into the EGR valve assembly.

3) I used a new piece of vacuum line, about 2 inches long, to connect the new EGR assembly to the engine vacuum input. Be sure to order this along with the EGR valve assembly and metal gasket.

4) Not sure if this matters but the old metal gasket had a ridge in it. The ridge side was against the engine block and the valley side was against the EGR valve assembly. No sealant required.

5) I cleaned the EGR tube with carb cleaner. It was dirty but not clogged. The engine has 177,000 miles on it.

6) I carefully cleaned the gasket mating surface with carb cleaner and fine steel wool. I plugged the entry hole first so no shreds of steel wool would get in the engine.

7) There are two plastic clips on the breather snorkel that connect the snorkel to the engine. Both were brittle with age. The top one is very easy to snap.:frown
The bottom one can be reached from underneath if you are small and can rest your knees on the engine top. It is easy to see all three of the EGR hoses from this vantage point as well.

Reassembly was easy. I drove the car around the block and noticed that acceleration was much improved.

I hope this thread helps others who are contemplating the same repair.

One question for the experts - what is the purpose of the black cylindrical cap that hangs off a hose on the EGR valve assembly? It looks like it should plug into something but I could not locate any matching fitting.

Thanks to all and especially the person who made the video.
:thumbsup:
 

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It is the exhaust pipe for the vacuum.

The way it works:

Normally the solenoid part (it is basically a vacuum switch) is closed so no engine vacuum to the EGR valve (the vacuum operated valve that passes the exhaust to the intake when opens).

When the controller wants to inject exhaust, it opens the solenoid valve which in turn applies vacuum to the EGR valve and the valve opens.

To close the valve, the controller electrically closes the solenoid valve, the engine vacuum is then plugged, but the EGR valve needs to close again, so the vacuum that holds the EGR valve in open position is routed to this exhaust valve, and the EGR valve pressure is equalized to outside.. Without it, the EGR valve would have stayed closed with the leftover vacuum.
 

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One question for the experts - what is the purpose of the black cylindrical cap that hangs off a hose on the EGR valve assembly? It looks like it should plug into something but I could not locate any matching fitting.

Thanks to all and especially the person who made the video.
:thumbsup:
It is a vent. After EGR valve test is completed air is admitted through it to allow EGR valve to close.
 

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I cleaned the EGR tube with carb cleaner. It was dirty but not clogged. The engine has 177,000 miles on it.
I removed the tube too and it was 25 percent clogged for a car near 200k miles. The amount of exhaust injected is actually very little, modulated by the solenoid, so even 75 percent blockage should be fine. So the removal of the tube was not completely necessary in my case. The replacement of the EGR valve only would have reduced my time substantially.
 
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