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Pelican Technical Article:

Valve Cover Removal

Steve Vernon

Time:

4 hours4 hrs

Tab:

$20

Talent:

***

Tools:

T30, T25 Torx, E10 Torx, 17mm wrench

Applicable Models:

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

Parts Required:

Sealant

Hot Tip:

Clean around the covers before removing

Performance Gain:

No oil leaks

Complementary Modification:

Replace worn out hoses

The valve covers on the C350 have no gasket between the cover and the head. There is only a thin film of sealant used to seal up the top of the motor. The cover is also used to hold the cams in place and incorporate the journal for the cams. The covers are also not interchangeable with other heads so if you damage it while working on it you need to replace the head as well as the cover. For this reason USE great care!

The procedures for replacing the left and right side are very similar but do have a few differences that are pointed out below. You have to move different accessories out of the way depending on whether you are working on the right or left side.

If you remove the left valve cover you are going to be disconnecting the fuel line so the first step is to prep the car. I like to tell people to pull the fuel pump relay and then try to start the car. The car will turn over and then die. Do this about 2-3 times - it will help drain excess fuel out of your system. Also open the gas cap to help depressurize the system. Then, make sure that the car has cooled down; you don't want to be working with gasoline when the car is hot.

Have a fire extinguisher handy. There will be some spillage of fuel as it's nearly impossible to prevent. Also, wear chemical resistant gloves if you don't want to get any gasoline on your hands. Make sure that you have plenty of paper towels or rags to help you clean up. Perform the injector removal in a clear, open, and well-ventilated space. It may not hurt to have an assistant around in case there are any problems.

Again, the covers are also not interchangeable with other heads. If you damage it while working on it you cannot order a replacement cover and need to replace the head as well as the cover. Be very careful!

Right Side Valve Cover- You will need to remove the front (red arrow) and rear (yellow arrow) engine covers along with the air ducts (green arrows).
Figure 1

Right Side Valve Cover: You will need to remove the front (red arrow) and rear (yellow arrow) engine covers along with the air ducts (green arrows). Please see our article on engine cover removal for additional assistance.

Right Side Valve Cover- Pull out the wring connection slide clamp on the right side of the ECU (red arrow).
Figure 2

Right Side Valve Cover: Pull out the wring connection slide clamp on the right side of the ECU (red arrow). This will disconnect the harness from the ECU.

Right Side Valve Cover- Tilt the ECU back out of the way with the left side wiring connection still attached (red arrow).
Figure 3

Right Side Valve Cover: Tilt the ECU back out of the way with the left side wiring connection still attached (red arrow). Use a T30 Torx and remove the ECU mount on the right side of the intake manifold (yellow arrows).

Right Side Valve Cover- Use an E10 Torx and remove the fasteners holding the wiring loom in place (red arrows) on the right side valve cover.
Figure 4

Right Side Valve Cover: Use an E10 Torx and remove the fasteners holding the wiring loom in place (red arrows) on the right side valve cover. Use a T30 Torx and remove the single Torx screw connecting the wiring loom harness to the intake manifold (yellow arrow).

Right Side Valve Cover- Disconnect the wiring from the coils by using a small screwdriver and pushing the clip back (red arrow).
Figure 5

Right Side Valve Cover: Disconnect the wiring from the coils by using a small screwdriver and pushing the clip back (red arrow).

Right Side Valve Cover- Gently squeeze the clip and slide the connections off (red arrow).
Figure 6

Right Side Valve Cover: Gently squeeze the clip and slide the connections off (red arrow).

Right Side Valve Cover- Use an E10 Torx and remove the bolt holding the ground wire in place (red arrow) on the valve cover.
Figure 7

Right Side Valve Cover: Use an E10 Torx and remove the bolt holding the ground wire in place (red arrow) on the valve cover.

Right Side Valve Cover- Use a T30 Torx and remove the two bolts holding the coil in place on each of the three coils (red arrows).
Figure 8

Right Side Valve Cover: Use a T30 Torx and remove the two bolts holding the coil in place on each of the three coils (red arrows). With the bolts removed pull the coils straight up and out from the spark plugs.

Right Side Valve Cover- Disconnect all of the wiring connections on the front of the cylinder head (red arrows).
Figure 9

Right Side Valve Cover: Disconnect all of the wiring connections on the front of the cylinder head (red arrows).

Right Side Valve Cover- Remove the four E10 Torx bolts and then the breather cover on the rear of the right cylinder head (red arrow).
Figure 10

Right Side Valve Cover: Remove the four E10 Torx bolts and then the breather cover on the rear of the right cylinder head (red arrow).

Right Side Valve Cover- Slide the wiring harness out of the way.
Figure 11

Right Side Valve Cover: Slide the wiring harness out of the way. Use an E10 Torx to remove the three bolts along the top of the front valve cover that hold it to the top valve cover (red arrows).

Right Side Valve Cover- You can move the wiring harness out of the way and remove the bolts holding the cover in place.
Figure 12

Right Side Valve Cover: You can move the wiring harness out of the way and remove the bolts holding the cover in place. Use this photo to show the loosening pattern. If you need to you can use a T25 and remove the rubber engine lid mounts.

Right Side Valve Cover- There are three places on the cover that you can insert the coil bolts and safely tighten them to loosen and separate the cover from the head (red arrows).
Figure 13

Right Side Valve Cover: There are three places on the cover that you can insert the coil bolts and safely tighten them to loosen and separate the cover from the head (red arrows). There are two places that you can place a pry bar between the front cover and the valve cover and safely separate them (yellow arrows). Never pry anything between the metal surfaces or mounting surfaces.

Right Side Valve Cover- By installing one of the coil bolts into the valve cover and then tightening it the bolt will press safely against the head and separate the valve cover from the head (red arrow).
Figure 14

Right Side Valve Cover: By installing one of the coil bolts into the valve cover and then tightening it the bolt will press safely against the head and separate the valve cover from the head (red arrow).

Right Side Valve Cover- Now you can safely remove the cover.
Figure 15

Right Side Valve Cover: Now you can safely remove the cover.

Right Side Valve Cover- Completely clean any remaining sealant off of the cover.
Figure 16

Right Side Valve Cover: Completely clean any remaining sealant off of the cover. Never use anything metal or any form of sandpaper as this can affect the ability of the cover to completely seal with the head. The cover is also used to support the camshafts and the cam journal built into the cover. Make sure these are very clean before installation.

Right Side Valve Cover- While Mercedes recommends using Loctite 7200 to seal the surfaces I have always used Drei Bond 1209 with good results.
Figure 17

Right Side Valve Cover: While Mercedes recommends using Loctite 7200 to seal the surfaces I have always used Drei Bond 1209 with good results.

Right Side Valve Cover- Apply a bead of sealant using the path shown here.
Figure 18

Right Side Valve Cover: Apply a bead of sealant using the path shown here. The bead must be 1mm thick (+/-0.2mm), and the cover must be installed within ten minutes of applying the sealant.

Right Side Valve Cover- Lightly oil the cams with some engine oil where they meet the journals in the cover.
Figure 19

Right Side Valve Cover: Lightly oil the cams with some engine oil where they meet the journals in the cover. This is the tightening pattern for torqueing the valve covers down. The covers are torqued in two stages. The first torque value is 12Nm. The second stage is to tighten the bolts an additional 90 degrees.

Left Side Valve Cover- The left side valve covers are the same procedures as the right with the following differences.
Figure 20

Left Side Valve Cover: The left side valve covers are the same procedures as the right with the following differences. Disconnect the two electrical connections on the fuel rail (red arrows) and slide the electrical connection off the rail (yellow arrow).

Left Side Valve Cover- Use an E10 Torx and remove all the wiring harness connectors from the left side bank (red arrows) including the one on the lift eye on the rear.
Figure 21

Left Side Valve Cover: Use an E10 Torx and remove all the wiring harness connectors from the left side bank (red arrows) including the one on the lift eye on the rear.

Left Side Valve Cover- Even though the engine should have been sitting overnight and you have removed the fuel pump relay to try and get the fuel out of the rail there will still be some.
Figure 22

Left Side Valve Cover: Even though the engine should have been sitting overnight and you have removed the fuel pump relay to try and get the fuel out of the rail there will still be some. Unscrew the Schrader valve cap and wrap a screwdriver in a rag and press in the end of the Schrader valve (red arrow). This will release the remaining pressure in the system. Gas will come out so be prepared to catch and dispose of it according to the regulations in your area.

Left Side Valve Cover- Use a 17mm wrench and separate the fuel line from the distribution rail (red arrow).
Figure 23

Left Side Valve Cover: Use a 17mm wrench and separate the fuel line from the distribution rail (red arrow).

Left Side Valve Cover- Use an E10 Torx and remove the AOS (red arrow).
Figure 24

Left Side Valve Cover: Use an E10 Torx and remove the AOS (red arrow). Two of the valve cover bolts are located under the AOS (yellow arrows).

Left Side Valve Cover- After following the procedures for removing the electrical work similar to the right side this photo illustrates the loosening and tightening sequence for the left side.
Figure 25

Left Side Valve Cover: After following the procedures for removing the electrical work similar to the right side this photo illustrates the loosening and tightening sequence for the left side. Note the paper towel in the AOS opening; this is to prevent anything from falling in while removing the bolts. Follow the same instructions for sealing and reinstalling the left side cover.

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Comments and Suggestions:
Sunny Comments: What tool do you use to remove the breather cover? The space is very small and my hand and 1/4" drive couldnt fit in between the heat shield and the screws.
April 2, 2016
  Followup from the Pelican Staff: Try an open ended E10 wrench. - Nick at Pelican Parts  
Sunny Comments: What do you use to clean the inside of the valve covers with?
April 2, 2016
  Followup from the Pelican Staff: Warm water and soap. Be sure it is wiped dry before reinstalling. - Nick at Pelican Parts  

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