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Valve Cover Gasket Replacement
 
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Pelican Technical Article:

Valve Cover Gasket Replacement

Steve Vernon

Time:

2 hours2 hrs

Tab:

$15 to $20

Talent:

**

Tools:

10mm socket, 5mm Allen, screwdriver

Applicable Models:

Mercedes-Benz W124 (1986-95)

Parts Required:

New valve cover gasket set

Hot Tip:

Make sure the new gasket is properly seated

Performance Gain:

No oil leaks

Complementary Modification:

New air filter

Valve covers have a tendency to eventually leak oil making a mess of the engine. While it is not difficult to change the valve cover gasket on the Mercedes-Benz M104 engine you will need to remove a few things first. One thing that a beginning DIY'er thinks will help but only causes problems is putting RTV sealant on the head or gasket. A properly clean, seated and tightened valve cover and seal does not need any RTV. Most people lather on the RTV which just ends up getting into the valve train and causing all kinds of problems. If you do the job correctly and there are no problems with the head or valve cover you do NOT need to use RTV.

It is a very good idea to perform this work when the engine is cold.

To remove the valve cover you will need to remove the wiring for the spark plugs.
Figure 1

To remove the valve cover you will need to remove the wiring for the spark plugs. The plugs can remain in the engine. The six spark plugs on the M104 engine are located under a cover on the top of the valve cover (red arrow). You will need to remove the air intake tube (green arrow) to get access to the coils and wires.

Start by disconnecting the MAF sensor.
Figure 2

Start by disconnecting the MAF sensor. The MAF is held in place by two clips to the air filter box (red arrow, one shown, one below) a single clamp to the intake tube (yellow arrow) and the wiring harness (green arrow).

Turn the locking ring on the harness (red arrow) counter clockwise; this will separate it from the connection on the MAF (yellow arrow).
Figure 3

Turn the locking ring on the harness (red arrow) counter clockwise; this will separate it from the connection on the MAF (yellow arrow).

Separate it from the air filter lid by pulling back on the two clips (red arrows).
Figure 4

Separate it from the air filter lid by pulling back on the two clips (red arrows). You can leave the MAF attached to the tube and remove the MAF and tube together.

Remove the two 10mm nuts where the intake tube attaches to the valve cover (red arrows).
Figure 5

Remove the two 10mm nuts where the intake tube attaches to the valve cover (red arrows).

Disconnect the air intake temperature sensor (red arrow).
Figure 6

Disconnect the air intake temperature sensor (red arrow).

There is a single hose clamp that holds the intake tube to the throttle body.
Figure 7

There is a single hose clamp that holds the intake tube to the throttle body. You will need to reach between the water pump and the intake runners with a long flathead screwdriver (red arrow) to loosen the clamp. With the clamp loose remove the intake tube and MAF from the top of the engine.

There are six 5mm Allen head bolts that hold the access panel to the top of the valve cover (red arrows).
Figure 8

There are six 5mm Allen head bolts that hold the access panel to the top of the valve cover (red arrows).

Use a 5mm Allen and remove the bolts and washers (red arrow).
Figure 9

Use a 5mm Allen and remove the bolts and washers (red arrow).

There is a diagram on the top of the cover that illustrates the coil and plug distribution (red arrow).
Figure 10

There is a diagram on the top of the cover that illustrates the coil and plug distribution (red arrow).

Remove the cover from the top of the engine (red arrow).
Figure 11

Remove the cover from the top of the engine (red arrow).

This photo illustrates how the number 6 coil also fires the number 1 plug (red arrows).
Figure 12

This photo illustrates how the number 6 coil also fires the number 1 plug (red arrows). The number 2 coil also fires the number 5 plug (yellow arrows). The number 4 coil also fires the number 3 plug (green arrows). You are going to be removing the coils and wire connectors completely from the head so it is a good idea to number them first for ease of reinstallation.

Separate the wiring harness from the coils (red arrow).
Figure 13

Separate the wiring harness from the coils (red arrow).

With the three coil wire disconnected remove the harness from the top of the engine (red arrow).
Figure 14

With the three coil wire disconnected remove the harness from the top of the engine (red arrow).

Pull the spark plug connectors up by the hard plastic part (red arrow).
Figure 15

Pull the spark plug connectors up by the hard plastic part (red arrow). Never pull the connector up from the wires.

You can pull the connector for the coil over plugs up by the coil itself (red arrow).
Figure 16

You can pull the connector for the coil over plugs up by the coil itself (red arrow). Remove the coils and plug connectors from the engine.

You are going to remove the twelve 10mm bolts that hold the valve cover on (red arrows).
Figure 17

You are going to remove the twelve 10mm bolts that hold the valve cover on (red arrows). It is a good idea to loosen and tighten these bolts in a crisscross pattern.

The two bolts along the right side of the valve cover hold a bracket for the vacuum line (red arrows).
Figure 18

The two bolts along the right side of the valve cover hold a bracket for the vacuum line (red arrows).

The bolts are long and sit in a metal sleeve (red arrow).
Figure 19

The bolts are long and sit in a metal sleeve (red arrow). At the top of each bolt is a rubber washer and large washer (yellow arrow). Do not loose these.

There are two areas in the front of the valve cover that you can use to help separate the cover from the head (red arrow).
Figure 20

There are two areas in the front of the valve cover that you can use to help separate the cover from the head (red arrow). Tapping the cover with a soft rubber mallet can also help. NEVER pry on the surfaces between the head and cover. This will only cause gouging in the metal and eventual oil leaks. Never hit the cover with a hard hammer, this can lead to a cracked valve cover and an expensive purchase to replace it.

Remove the cover from the front taking care to clear all the lines and wiring on the rear (red arrow).
Figure 21

Remove the cover from the front taking care to clear all the lines and wiring on the rear (red arrow).

Remove the old seal around the edge (red arrow) as well as the seals around the spark plug openings (yellow arrow).
Figure 22

Remove the old seal around the edge (red arrow) as well as the seals around the spark plug openings (yellow arrow). Thoroughly clean the cover making sure to completely remove the old gasket. You can use something made of wood to clean the grooves. Never clean the groves of the cover with anything metal or a screwdriver.

Thoroughly clean the matting surface on the head (red arrow) making sure to include the area where the spark plug gaskets will sit (yellow arrow).
Figure 23

Thoroughly clean the matting surface on the head (red arrow) making sure to include the area where the spark plug gaskets will sit (yellow arrow). Install the new gaskets onto the valve cover and then lower the cover onto the head making sure that everything is sitting flush and that the gasket did not slip off the cover. Tighten and torque the valve over in a crisscross pattern starting from the bolt near the spark plug openings. Installation is the reverse of removal.









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Comments and Suggestions:
Ando Comments: What would be the torque spec. for the bolts holding down the valve cover be?

Thanks
November 3, 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
 
Phil K Comments: Do you stock the "six 5mm Allen head bolts" which attach the spark plug access panel to the valve cover? They are noted in figure 8. Can't seem to find them
April 3, 2015
  Followup from the Pelican Staff: I am sure we have them.

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
 

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