Techs have frequently posted that an egr problem is not usually caused by an inoperative valve (a sticking valve, or a valve stuck in the open or closed position), but rather a problem with a clogged hot inlet pipe that goes from the egr valve to the intake manifold.

This problem is well documented on M104 engines, and a mechanic who specializes in Mercedes should be well aware of the problem.

Steve Brotherton (Stevebfl), has an article posted written under the DIY link at the top of the page under Evaluating Electronic Engine Controls that illustrates the problem, with a picture, at the end of the article.

The plug is caused by a build-up of carbon from oily pcv vapors, and always occurs where this pipe enters the intake manifold.

There are two options to solve the problem:

1. remove the build up by inserting a long wire, like a speedometer cable, and reaming it out with a drill motor.

2. replace the hot inlet pipe with a new one. They have been redesigned, and the pipe is a little longer where it enters the intake manifold, solving the problem permanently.

There is still a chance your egr valve is bad, and it can be designed by pulling a vacum with a hand held pump.

Use the search function to find posts on the procedure to check if a valve is bad or not.

There are also numerous postings on guys that have gone the speedometer cable route.

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Paul S.

2001 E430, Bourdeaux Red, Oyster interior.
79,200 miles.

1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".