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Air Oil Separator Replacement
 

Pelican Technical Article:

Air Oil Separator Replacement

Steve Vernon

Time:

1 hour1 hr

Tab:

$15 to $45

Talent:

**

Tools:

T10 Torx

Applicable Models:

Mercedes-Benz C350 (2008-14)
Mercedes-Benz GLK350 (2010-14)

Parts Required:

Air oil separator

Hot Tip:

Use caution working with old hoses

Performance Gain:

Car runs like normal again

Complementary Modification:

Replace vacuum hoses

The air oil separator on the C350 can wear out and fail over time. Most of the time the gasket fails on the separator and starts leaking oil onto the head. If your separator is failing replacement is quick and easy.

You will need to remove the engine covers (red and yellow arrows) and air intake ducts (green arrows).
Figure 1

You will need to remove the engine covers (red and yellow arrows) and air intake ducts (green arrows). Please see our article on engine cover removal for additional assistance.

The air oil separator is located on the top front of the left valve cover (red arrow).
Figure 2

The air oil separator is located on the top front of the left valve cover (red arrow). The hose from the separator runs along beside the intake manifold and attaches to the top of the throttle body (yellow arrow). This hose gets dried out and brittle over time so when working with it use care.

This photo illustrates the AOS (red arrow).
Figure 3

This photo illustrates the AOS (red arrow). Begin by using your hand and slipping the vacuum hose out from the mount on the side of the AOS (yellow arrow).

Next use an E10 Torx and remove the three bolts (red arrows).
Figure 4

Next use an E10 Torx and remove the three bolts (red arrows).

Pull the AOS off the valve cover and gently separate the hose from the top of the AOS (red arrow).
Figure 5

Pull the AOS off the valve cover and gently separate the hose from the top of the AOS (red arrow). These hoses get very old and brittle so use care.

With the separator off there is a direct hole into the valve train so make sure you plug it right away with a cloth or paper towel.
Figure 6

With the separator off there is a direct hole into the valve train so make sure you plug it right away with a cloth or paper towel. If something falls in there you will have to remove the valve cover to get it out.

If you have removed the separator for any other reason than replacement and are reinstalling it make sure to replace the gasket (red arrow).
Figure 7

If you have removed the separator for any other reason than replacement and are reinstalling it make sure to replace the gasket (red arrow). Installation is the reverse of removal. Note: Update: at this time the gasket is not available individually; check for availability when ordering. 

Comments and Suggestions:
Steve W. Comments: Buck, no the oil separator is air. Sounds strange but that won't get affected by the wrong oil.
October 27, 2016
  Followup from the Pelican Staff: Thanks for the input on this one. We appreciate the help.
- Nick at Pelican Parts
 
Buck Comments: By putting in the wrong oil on a oil change. Can you damage the oil separator.
October 22, 2016
  Followup from the Pelican Staff: No. - Nick at Pelican Parts  

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Page last updated: Sun 12/17/2017 02:55:20 AM