MB Medic Mercedes-Benz Repair Guides, Service, How To DIY
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In this guide (5 sections)
Purpose
This guide will show you how to replace the EGR mixing chamber, the housing where the EGR valve feeds exhaust gas into the charge air on the OM611 and OM612 engines. Over time it fills with soot and oil residue from the EGR and the crankcase vent, which restricts airflow and shows up as a rough idle, poor throttle response and black smoke. For the wider picture, see our guide to common Mercedes-Benz CDI diesel problems.
Application
1999 W210 E-Class and 2000 W203 C-Class 220 CDI
2000 W90x Sprinter and G-Wagen G 270 CDI
Parts Required
New Mixing Chamber and Gasket.
Removal and Installation Instructions
Work on a cold engine: the mixing chamber bolts to the charge air pipe right where the EGR feed comes off the exhaust side, and it stays hot long after shutdown.
- Disconnect the battery negative terminal.
- Open the hood of your Mercedes-Benz.
- Locate the charge air distribution pipe. Remove the vacuum hoses. Remove the charge air hose from the mixing chamber.
- Remove the bolts that hold the mixing chamber on the charge air distribution pipe. Make sure to remove the gasket carefully.
- Remove the old EGR mixing chamber. Install the new mixing chamber in reverse order. Ensure that all surfaces are clean.
- Inspect the condition of the old EGR/ Mixing chamber.
- It is recommended that you replace the old gasket. You need to make sure there will not be any leakage at the gasket.
- Tighten the bolts that hold the mixing chamber. If you are using a torque wrench, tighten to 11 Nm.
Conclusion
Once you replace the EGR mixing chamber and reconnect the vacuum hoses, start the engine. If the old chamber was clogged with soot, the engine should idle more smoothly and pull better. Note that you may have to crank the engine a couple of times to get it to start after this repair.
Replacing the chamber does not clear what the engine control unit recorded while it was clogged. If the check engine light was on, the EGR fault code stays stored until it is read and cleared, and if the light comes back the cause is upstream of the chamber: a sticking EGR valve, a split vacuum line or a tired vacuum transducer, none of which a new chamber fixes. A scanner that reads every control unit, such as the UCAN-II Pro, reads and clears the engine codes on the OM611 and OM612 and lets you watch the EGR duty cycle and the air mass reading live, which is how you tell whether the valve is actually opening. If you want to compare options first, see our roundup of OBD2 scanners for Mercedes-Benz diesels.
Before you buy parts, scan every control module, not just the engine. It shows the root fault behind the warning lights and tells you whether the problem is still active. See how to do a full health check.
