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Replacing Your Mercedes Change Over Valve
 
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Pelican Technical Article:

Replacing Your Mercedes Change Over Valve

Steve Vernon

Time:

30 minutes30 mins

Tab:

$45

Talent:

*

Tools:

Hands

Applicable Models:

Mercedes-Benz ML320 (1998-03)
Mercedes-Benz W203 (2001-07)

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 air pump change over valve. This article will show you how to replace the valve on a Mercedes-Benz W203.

Begin by disconnecting the ground from the battery and making sure it can not accidentally make contact again while you are working.

You will need to remove the right air inlet duct as well as the front engine cover.

Remove the duct by compressing it towards the engine and then slip it off the air inlet.

With the duct off remove the front engine cover. It pulls up and away from the engine. The cover is held on by five clips and will easily come off with hand pressure.

Now you have access to the air pump change over valve. The valve sits on the right side of the engine directly in front of the right side check valve. It is held in place by a plastic clip over the metal mount. Remove it from the mount by lifting it up; this will give you more room to work on remove the electrical connector. The wires and harness will be brittle from years of heat. Carefully remove the harness by squeezing in and pulling down.

Next remove the three vacuum attachments. Again, be careful as the hoses and lines can get very hard and brittle with age.

Installation is the reverse of removal.

Begin by disconnecting the ground from the battery and making sure it can not accidentally make contact again while you are working.
Figure 1

Begin by disconnecting the ground from the battery and making sure it can not accidentally make contact again while you are working.

You will need to remove the right air inlet duct (red arrows) as well as the front engine cover (yellow arrow) to get access to the air filter housing on top of the engine.
Figure 2

You will need to remove the right air inlet duct (red arrows) as well as the front engine cover (yellow arrow) to get access to the air filter housing on top of the engine.

Remove each duct by compressing them towards the engine (red arrow) and slipping them off the air inlet.
Figure 3

Remove each duct by compressing them towards the engine (red arrow) and slipping them off the air inlet.

With the ducts off remove the front engine cover.
Figure 4

With the ducts off remove the front engine cover. It pulls up and away from the engine (yellow arrow).

The cover is held on by five clips (red arrows) and will easily come off with hand pressure.
Figure 5

The cover is held on by five clips (red arrows) and will easily come off with hand pressure.

Now you have access to the air pump change over valve (red arrow).
Figure 6

Now you have access to the air pump change over valve (red arrow). The valve sits on the right side of the engine directly in front of the right side check valve. It is held in place by a plastic clip over the metal mount (yellow arrow).

Remove it from the mount by lifting it up; the plastic clip (green arrow) is part of the valve.
Figure 7

Remove it from the mount by lifting it up; the plastic clip (green arrow) is part of the valve. This will give you more room to work on remove the electrical connector. The wires and harness will be brittle from years of heat. Carefully remove the harness by squeezing in and pulling down (red arrow).

Next remove the three vacuum attachments (yellow, red and green arrows).
Figure 8

Next remove the three vacuum attachments (yellow, red and green arrows). Again, be careful as the hoses and lines can get very hard and brittle with age.

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Comments and Suggestions:
petike Comments: Hi there
I have 02 CL203 C180 2000ccm. Could you please describe, which vacuum hoses where have to connecting pls?
Which one take the vacuum to EGR, etc ... etc.
Thanks
Peter
September 19, 2015
  Followup from the Pelican Staff: I don’t have that info.

I would grab a repair manual. It will have the procedure, special tools and torque specs.

Give our parts specialists a call at 1-888-280-7799. - Nick at Pelican Parts
 
mike Comments: Hi my name is mike and I have a beautiful 1992 400e Mercedes benz and iam having trouble passing the emission. I have change everything that the people told me to change, everybody say they cant understand as good as this car run and sound I believe it is something simply can you please help me.
July 29, 2015
  Followup from the Pelican Staff: What fault code is is setting? - Nick at Pelican Parts  
Michelle Comments: Hi I have a 2007 Mercedes c230 and I Need the switchover valve mine completely gone, I was hoping you could help me find the one I need also need the engine cover. Thank you
June 8, 2015
  Followup from the Pelican Staff: Give our parts specialists a call at 1-888-280-7799. They can figure out what part or repair kit you need.
- Nick at Pelican Parts
 
Alcon Comments: I mean. I got a 01 Mercedes C320 I found disconnected two houses on the change over valve and i don't know if one has to be connected on the top and one on the lower part. I whach your picture. On top is clear but down i can't see if is the other tube or only the little filter.thanks again.
June 5, 2015
  Followup from the Pelican Staff: Use the emission label under your hood. There should be a vacuum diagram. The solenoid should have an arrow for direction of flow. - Nick at Pelican Parts  
Alcon Comments: Can you tell me y the change over valve has to have connected a house down or only two on top thanks
June 4, 2015
  Followup from the Pelican Staff: Sorry, I don't understand the question. Can you expand on what you need help with? - Nick at Pelican Parts  
877gilles Comments: Nick, you replied to MBML320 to manually activate the valve to see if the vacuum direction switches. How do you do that?
Thanks
877gilles
April 24, 2015
  Followup from the Pelican Staff: It is an electronic solenoid. You can supply your own fused power and ground to the solenoid (when it is unplugged). Test vacuum blocking and passing using a hand pump. - Nick at Pelican Parts  
MBML320 Comments: How can you test the change over and check valves to know what parts to replace?
November 28, 2014
  Followup from the Pelican Staff: You can check if the solenoid is receiving vacuum, then manually activate it and see if the vacuum direction switches.

For check valves, they should block exhausts flow, then allow flow to the exhaust when opened. - Nick at Pelican Parts
 
jorge Comments: This is the valve that needs to be replace in my 2006 mercedes c280. I requested this part and provided the vin no.
November 17, 2014
  Followup from the Pelican Staff: Give our parts specialists a call at 1-888-280-7799 and they can help figure out which part or repair kit you need.
- Nick at Pelican Parts
 
soulman Comments: Hi there once again. This unit - switch over valve what exactly does it do, & when does it switches on
October 9, 2014
  Followup from the Pelican Staff: This valve allows or blocks vacuum flow to the secondary air check valve. - Nick at Pelican Parts  

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