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Replacing YourMercedes Breather Hoses
 
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Pelican Technical Article:

Replacing YourMercedes Breather Hoses

Steve Vernon

Time:

2 hours2 hrs

Tab:

$20

Talent:

*

Tools:

Flat head screw driver

Applicable Models:

Mercedes-Benz W203 (2001-07)

Parts Required:

New hoses

Hot Tip:

Remove the MAF housing

Performance Gain:

Pass a SMOG test

Complementary Modification:

Replace air filter

The crank case breather hoses are part of the engines system designed to keep harmful emissions from getting out into the environment. The hose recirculation fumes and gases from within the engine block back into the combustion chamber to be burnt clean. There are three breather hoses on the Mercedes C320 and if you are performing any work on the injectors, MAF or valve gaskets that involve moving the hoses you can pretty much count on replacing them. The hoses sit on top of the valve covers and get extremely hard and brittle with age. There is one hose on the right side and two hoses on the left. While the right side hose traditionally last longer than the other two, if you are going to be working around the heads plan on replacing all three.

You will need to remove the air filters to complete this job. Please see our article on replacing your air filters.

Installation is the reverse of removal.

The right side hose connects to the top of the right side valve cover (red arrow).
Figure 1

The right side hose connects to the top of the right side valve cover (red arrow). If it is still pliable slide it off where it connects. If it is not, it is easier to just cut it off as you are going to be replacing it anyway.

There are two hoses connected on the left side (red arrows).
Figure 2

There are two hoses connected on the left side (red arrows). If they are still pliable slide them off where they connect and then go celebrate as you are the first person I have ever heard of to successfully remove them without damaging them. If they are not, it is easier to just cut them off as you are going to be replacing them anyway.

The larger hose on the left side connects down onto the lower part of the MAF housing (red arrow).
Figure 3

The larger hose on the left side connects down onto the lower part of the MAF housing (red arrow). It is very difficult to reach. If you have small hands you may be able to remove the old hose and attach the new on with the housing in place, but I find it easier to remove the MAF housing. It is easy, quick to do and we have an article on it to walk you through it.

The smaller hose on the left side is two pieces (red arrow), and can usually be separated by the MAF connection for easier replacement.
Figure 4

The smaller hose on the left side is two pieces (red arrow), and can usually be separated by the MAF connection for easier replacement. The yellow arrow shows the area you need to work in if you are leaving the MAF housing on when replacing the larger hose.

With the MAF housing off you can see where the left side hose (green arrow) and the right side hose (yellow arrow) join by the throttle body (red arrow).
Figure 5

With the MAF housing off you can see where the left side hose (green arrow) and the right side hose (yellow arrow) join by the throttle body (red arrow).

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Comments and Suggestions:
andyd987 Comments: Pictures are not the same as the set up on my 2002 C230K w/M111 engine. Similar yes.
June 21, 2015
  Followup from the Pelican Staff: Thanks for the additional info and feedback. We appreciate it.
- Nick at Pelican Parts
 
Todd Comments: There are a few misleading things about these photos. Chief among them is that you show the wiring harness "plenum" and the fuel line removed. I'm sure that having them out of the way makes it easier to show the job, but it would help to see the removal process.
November 22, 2014
  Followup from the Pelican Staff: Thanks for the note. I will have it looked into and see if the article need sot be updated. - Nick at Pelican Parts  
rami Comments: Can you please tell me what part number is involved with each picture so i know what to buy? Thanks
September 28, 2014
  Followup from the Pelican Staff: I don;t have those numbers handy. Give our parts specialists a call at 1-888-280-7799. They can help you find the right part.
- Nick at Pelican Parts
 
J Comments: should of put part numbers on each part that was replace
June 29, 2014
  Followup from the Pelican Staff: Thanks. It looks like the parts link isn't working. I will have someone fix it.- Nick at Pelican Parts  

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