EGR pronlem
 

My Mercedes diesel EGR throws a trouble code. I use my OBD reader and clear it. Sometimes it clears itself.

Can anyone recommend an additive that will clean out the valve? This is getting irritating.

My only experience with an EGR valve was on an old Datsun B210. It had, I believe, a rubber bellows that allowed the thing to operate relative to engine vacuum, dumping exhaust into the intake stream at anything above idle. That said, when the rubber bellows piece dies, so does the EGR valve, unless the Mercedes version is rebuildable. YMMV.

In my experience, egr valves get plugged up w carbon and need to be removed and cleaned out, then they generally work ok again. If they are vacuum operated, obviously the vacuum element needs to be good. I'd remove it, scrape out all of the carbon you can with a small screwdriver or similar tool over the trash can and then clean it really good with WD-40 and a wire toothbrush. Squirt the WD in the moving parts while opening it and closing it, usually it's a small shaft that moves longitudinally when it opens.

I clean them all the time and then they work like new until they get carbon-ed up again but that takes years and miles.

No fuel additive really reaches the EGR valve in normal use. You need to remove it to clean it out. I have had some luck soaking in Seafoam to loosen deposits, but a screwdriver or pick works just as well. Also check the lines to / from the valve for deposits.

Light is off again.....