Mercedes EGR valve and cooler faults

Which Mercedes models are affected?

This page covers Mercedes engines fitted with an EGR valve, the valve that returns a measured amount of exhaust gas to the engine’s intake. Some systems also have an EGR cooler.

We do not list models here, because the valve, the cooler and the way they are tested vary from engine to engine. Put your registration in the enquiry form and we will check which system your car has. For other Mercedes work, see our Mercedes specialist page.

What are the symptoms?

The signs of an EGR fault include:

• the engine warning light
• poor running
• an emissions fault

A failed EGR valve is also one of the listed causes of faults in the SCR system, the part of the exhaust that uses AdBlue. If you have an AdBlue warning as well, see our AdBlue fault page.

When you book, tell us which warning lights are on and when the running problem happens.

What causes it?

There are two kinds of cause:

• contamination: oil mist and soot from the exhaust gas build up and stop the valve moving freely
• a fault in the valve’s actuator or one of its sensors

How do you confirm the cause before fitting parts?

A fault code is not a repair. An EGR valve can pass its electrical tests and still be contaminated, so a test on its own is not enough. Before we quote for any parts, we:

• read the fault memory using our diagnostic equipment
• run an actuator test on the valve
• remove and inspect the valve for soot and oil build-up
• inspect the EGR cooler where one is fitted

We then show you what we found, with photos, and send a written price. No part is fitted until you approve it in writing.

What does the repair involve?

Depending on what the inspection finds, we clean the valve or replace it. We tell you which we recommend and why. Where an EGR cooler is fitted and the inspection shows it is at fault, we replace it.

We repair EGR systems and keep them working: we do not remove or disable them. A missing, obviously modified or obviously defective EGR valve is a Major defect at the MOT.

Once the work is done, we check that the fault has cleared and verify the repair, including a road test where appropriate.

How long does an EGR repair take?

It depends on what the tests find, and on whether the valve can be cleaned or needs replacing.

Before any work starts, you get a written price and a promised time for your next update. If the car needs to stay with us, ask about a courtesy car when you book.

Is there a recall for the EGR valve?

Whether a recall applies depends on the individual car, so check your registration on gov.uk. Mercedes-Benz UK’s own vehicle check also shows non-safety service measures. Recall work is done by the manufacturer’s network, not by us.