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EGR Change Over Valve Replacement
 
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Pelican Technical Article:

EGR Change Over Valve Replacement

Steve Vernon

Time:

30 minutes30 mins

Tab:

$135

Talent:

*

Tools:

10mm socket

Applicable Models:

Mercedes-Benz 300CE (1990-93)
Mercedes-Benz 300E (1990-93)
Mercedes-Benz 300TE (1989-92)
Mercedes-Benz E320 (1994-95)

Parts Required:

Change over valve

Hot Tip:

Use care working on old rubber hoses

Performance Gain:

Pass a smog test

Complementary Modification:

Air pump check valves

If your car is not passing a smog test, one of the things that could be wrong is the EGR change over valve. This article will show you how to replace the valve on a Mercedes-Benz W124. Use care when working with old vacuum line as they can become dry and brittle over the years. Also, the early W124s suffer from the biodegradable wiring harness; this should be the first place to check if the valve is not functioning properly.

The EGR change over valve is located on the front right side of the cylinder head (red arrow).
Figure 1

The EGR change over valve is located on the front right side of the cylinder head (red arrow).

If you are having problems with the change over valve one of the first places you should check is the wiring.
Figure 2

If you are having problems with the change over valve one of the first places you should check is the wiring. The W124 suffers from the biodegradable wiring harness. Check the two electrical connections for the valve. This photo illustrates a degraded harness; these wires have lost their sheaths and are touching raw wire to wire. You can clean this up and either plastic dip or electrical tape-wrap the wires. Do this before changing the valve.

Carefully note where each line goes as you disconnect them (red arrows).
Figure 3

Carefully note where each line goes as you disconnect them (red arrows). Use care removing the old lines as they become hard and brittle with age.

You will be able to disconnect the lower electrical connection while the valve is on the head (red arrow) but will need to remove the valve from the head to separate the upper connection (yellow arrow).
Figure 4

You will be able to disconnect the lower electrical connection while the valve is on the head (red arrow) but will need to remove the valve from the head to separate the upper connection (yellow arrow).

To remove the valve use a 10mm socket and remove the two 10mm bolts (red arrows).
Figure 5

To remove the valve use a 10mm socket and remove the two 10mm bolts (red arrows).

When installing the new valve make sure to reattach the ground wire (green arrow) on the upper mount and place the lower mount (red arrow) behind the EGR line bracket (yellow arrow).
Figure 6

When installing the new valve make sure to reattach the ground wire (green arrow) on the upper mount and place the lower mount (red arrow) behind the EGR line bracket (yellow arrow). Installation is the reverse of removal.

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Comments and Suggestions:
fefe Comments: Can you tell me where and send me a picture of the locaton of the EGR valve is located on 1999 Mercedes C280? Thank you
September 28, 2016
  Followup from the Pelican Staff: I don't have a photo to share. it is located on the rear of the engine, next to the throttle housing.

- Nick at Pelican Parts
 
Mike Comments: Figured out why I can't find the EGR valve on my '89 300e-it doesn't have one. It should be on the flat spot cast in the front bank exhaust manifold but it never did. I understand now that some states required it and others didn't. This is a Florida car and apparently it wasn't required.
April 25, 2016
  Followup from the Pelican Staff: Thanks for the follow up. We appreciate it.
- Nick at Pelican Parts
 
Mike Comments: It looks like the EGR valve on an '89 300e is a remarkably different part. Can you tell me where it's located and if it can be cleaned or must be replaced if it fails. Thanks, Mike
April 25, 2016
  Followup from the Pelican Staff: Your vehicle may not have one. Check the emission label under the hood. it will note if it is equipped with EGR. - Nick at Pelican Parts  
NickG Comments: I own a 1993 300E 2.8 M104 and seem to have a problem with surging at idle and at speed, after the engine warms up. I've replaced the OVP, the idle speed control unit it no longer surges beyond 1000 rpms, had the throttle body rebuilt BBA Reman found no issues, tightened the wires on the crankshaft sensor unit, and back in 2004 had the wiring harness replaced. I changed plugs and now after a month they are black running too rich?. I've also replaced the MAF with a new one.
I am about to dive into the vacuum system to check for leaks. I suspect the EGR on the car could be an issue. I've plugged the line to it and ran it for awhile, with no appreciable change. Comments?
July 7, 2015
  Followup from the Pelican Staff: EGR would cause a stall at idle. I would perform vacuum leak diagnosis. You may find your issue there. - Nick at Pelican Parts  
65beto Comments: Thank you sir

June 12, 2015
  Followup from the Pelican Staff: No problem. - Nick at Pelican Parts  
65beto Comments: Is this the first thing to check when the car has severe raw gas smell from the tail pipe when first start in the mornings?

Thank you
June 10, 2015
  Followup from the Pelican Staff: No. Check fuel pressure and injectors for a leak if you have raw fuel odor. - Nick at Pelican Parts  

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