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Replacing Your Mercedes Valve Cover Breather Gaskets
 
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Pelican Technical Article:

Replacing Your Mercedes Valve Cover Breather Gaskets

Steve Vernon

Time:

3

Tab:

$20

Talent:

**

Tools:

T-25, T-30, E10 Torx driver, RTV compound, rags, cleaner

Applicable Models:

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

Parts Required:

RTV (possible crankcase breather hoses)

Hot Tip:

Clean everything well

Performance Gain:

Cleaner engine

Complementary Modification:

Breather hoses

It is not bad enough that the Mercedes-Benz W203's valve covers leak over time but the fact that the breather gaskets leak as well is a surprisingly poor piece of engineering from Mercedes-Benz. If you have noticed that your valve covers are filthy with oil around the breather covers there is a very good chance the gaskets are going bad. Unfortunately they don't sell a gasket for the covers so you are going to have to use RTV to make your own. Repairing them is not that difficult, most of the job is cleaning, but this article will walk you through the steps.

You are going to have to remove the engine air ducts and covers to get access to them.

Remove each duct by compressing them towards the engine and slipping them off the air inlet.

With the ducts 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.

Next, you will need to remove the main engine cover that also houses the air filters. It is held on by four pressure clips. You can see the two at the front of the engine, to remove the housing lift it at the front of the engine and once the front clips release the rears (which you can not see) will release as well.

We are going to begin with the right side covers. You will be able to see the valve covers on top of the heads, they hold the coils. The breather cover is located just above the coils.

Disconnect the three individual wiring harnesses going to each coil. They simply squeeze in and pull out of the coil.

Next, remove the crankcase breather hose from the breather cover. If the hose is fairly new it should slide off. If the hose is original or old there is a very good chance it is dry and brittle and you are going to damage it and need to replace it. Do yourself a favor and order new hoses before you start this job.

Use a T-30 Torx and remove the three bolts holding the coil packs in place. With the bolts gone you can just swing the coils out of the way.

Use an E10 Torx and remove the two bolts on the breather cover.

Remove the two screws in the cover with a T25 Torx.

The cover is held on with RTV compound so you will have to wiggle it around to get the seal to break loose. Do not hit the plate or try and jam a screw driver between the valve cover and breather cover as this can damage both covers causing them to leak even more.

You do not have to clean every where on the two covers (unless you are going for a concourse look) but you do need to clean off all of the old gasket and clean any areas that mate.

After you have cleaned both surfaces, apply a small bead of RTV (Room Temperature Vulcanization) compound to the channel in the cover. Any good high-temp RTV sealant will do.

Apply the cover and torque to spec. You should see a small bead of compound around the two sealing surfac3es.

The left side of the engine is a little more involved, as the breather cover is larger, contains the oil fill opening in the cover and you need to move a few move things to get it off.

Disconnect the three individual wiring harnesses going to each coil. They simply squeeze in and pull out of the coil.

Use a T-30 Torx and remove the three bolts holding the coil packs in place. With the bolts gone you can just swing the coils out of the way.

You will need to move the small vacuum hose out of the way; it just unclips from the wiring harness holder. Unclip the wiring harness holder from the top of the fuel rail.

There is a small 6mm bolt that needs to be removed by where the harness meets the MAF sensor. Also the main wiring loom is clipped to the harness, unclip this as well.

You are going to have to remove both crankcase breather hoses from the breather cover. If the hoses are fairly new they should slide off. If the hoses are original or old there is a very good chance they are dry and brittle and you are going to damage them and need to replace them. I have actually never seen the hose on the left side of the engine come off without being damaged.

Do yourself a favor and order new hoses before you start this job.

Use an E10 Torx and remove the three bolts on the breather cover.

Use an E10 Torx and remove the three bolts on the breather cover.

Make sure to clean the area well and inspect for debris, sometimes the old gasket can fall back into the cover. Clean and replace the same as the right side cover.

Installation is the reverse of removal.

You will need to remove the two air inlet ducts (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 1

You will need to remove the two air inlet ducts (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 2

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 3

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 4

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

Next, you will need to remove the main engine cover that also houses the air filters.
Figure 5

Next, you will need to remove the main engine cover that also houses the air filters. It is held on by four pressure clips. You can see the two at the front of the engine (red arrows).

To remove the housing lift it at the front of the engine and once the front clips release the rears (which you can not see) will release as well (red arrows).
Figure 6

To remove the housing lift it at the front of the engine and once the front clips release the rears (which you can not see) will release as well (red arrows).

The two red arrows show the two breather covers, one on each valve cover.
Figure 7

The two red arrows show the two breather covers, one on each valve cover.

We are going to begin with the right side cover.
Figure 8

We are going to begin with the right side cover. You will be able to see the valve covers on top of the heads; they hold the coils (yellow arrows). The breather cover is located just above the coils (red arrow).

Disconnect the three individual wiring harnesses going to each coil (red arrows).
Figure 9

Disconnect the three individual wiring harnesses going to each coil (red arrows). They simply squeeze in and pull out of the coil. You can see how filthy the valve covers are in this picture.

Next remove the crankcase breather hose from the breather cover (red arrow).
Figure 10

Next remove the crankcase breather hose from the breather cover (red arrow). If the hose is fairly new it should slide off. If the hose is original or old there is a very good chance it is dry and brittle and you are going to damage it and need to replace it. Do yourself a favor and order new hoses before you start this job.

Use a T-30 Torx and remove the three bolts holding the coil packs in place.
Figure 11

Use a T-30 Torx and remove the three bolts holding the coil packs in place. With the bolts gone you can just swing the coils out of the way.

Use an E10 Torx and remove the two bolts on the breather cover.
Figure 12

Use an E10 Torx and remove the two bolts on the breather cover.

Remove the two screws in the cover with a T-25 Torx.
Figure 13

Remove the two screws in the cover with a T-25 Torx.

The cover is held on with RTV compound so you will have to wiggle it around to get the seal to break loose.
Figure 14

The cover is held on with RTV compound so you will have to wiggle it around to get the seal to break loose. Do not hit the plate of try and jam a screw driver between the valve cover and breather cover as this can damage both covers causing them to leak even more.

You do not have to clean every where on the two covers (unless you are going for a concourse look) but you do need to clean off the old gasket and clean any areas that mate.
Figure 15

You do not have to clean every where on the two covers (unless you are going for a concourse look) but you do need to clean off the old gasket and clean any areas that mate.

After you have cleaned both surfaces, apply a small bead of RTV compound to the channel in the cover.
Figure 16

After you have cleaned both surfaces, apply a small bead of RTV (Room Temperature Vulcanization) compound to the channel in the cover. Any good high temp RTV will do.

Apply the cover and torque to spec.
Figure 17

Apply the cover and torque to spec. You should see a small bead of compound around the two sealing surfaces (red arrow).

The left side of the engine is a little more involved, as the breather cover is larger (red arrows), contains the oil fill opening in the cover and you need to move a few move things to get it off.
Figure 18

The left side of the engine is a little more involved, as the breather cover is larger (red arrows), contains the oil fill opening in the cover and you need to move a few move things to get it off.

Disconnect the three individual wiring harnesses going to each coil (red arrows).
Figure 19

Disconnect the three individual wiring harnesses going to each coil (red arrows). They simply squeeze in and pull out of the coil.

Use a T-30 Torx and remove the three bolts (red arrows) holding the coil packs in place.
Figure 20

Use a T-30 Torx and remove the three bolts (red arrows) holding the coil packs in place. With the bolts gone you can just swing the coils out of the way.

You will need to move the small vacuum hose (red arrow) out of the way: it just unclips from the wiring harness holder.
Figure 21

You will need to move the small vacuum hose (red arrow) out of the way: it just unclips from the wiring harness holder. Unclip the wiring harness holder (yellow arrow) from the top of the fuel rail.

There is a small 6mm bolt (red arrow) that needs to be removed by where the harness meets the MAF sensor.
Figure 22

There is a small 6mm bolt (red arrow) that needs to be removed by where the harness meets the MAF sensor. Also the main wiring loom (yellow arrow) is clipped to the harness, unclip this as well.

You are going to have to remove both crankcase breather hoses (red arrows) from the breather cover.
Figure 23

You are going to have to remove both crankcase breather hoses (red arrows) from the breather cover. If the hoses are fairly new they should slide off. If the hoses are original or old there is a very good chance they are dry and brittle and you are going to damage them and need to replace them. I have actually never seen the hose on the left side of the engine come off without being damaged. Do yourself a favor and order new hoses before you start this job.

Use an E10 Torx and remove the three bolts (red arrows) on the breather cover.
Figure 24

Use an E10 Torx and remove the three bolts (red arrows) on the breather cover.

Use an E10 Torx and remove the three bolts (red arrows) on the breather cover.
Figure 25

Use an E10 Torx and remove the three bolts (red arrows) on the breather cover.

Make sure you clean the area well and inspect for debris (red arrow), sometimes the old gasket can fall back into the cover.
Figure 26

Make sure you clean the area well and inspect for debris (red arrow), sometimes the old gasket can fall back into the cover. Clean and replace the same as the right side cover.

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Comments and Suggestions:
proturner Comments: You guys rock with these Tech Articles. I had used some of your how-tos with my 72 911 and am happy to be back for a 98 clk 320.Thanks so much.
December 3, 2016
Rob Comments: which is the best quality MERCEDES BENZ Genuine sealant compound should I use for Top breather valve covers as they are slghtly leaking
July 27, 2016
  Followup from the Pelican Staff: See the genuine Benz RTV on this page, top of the list:

http://www.pelicanparts.com/cgi-bin/ksearch/pel_search_2014.cgi?SUPERCAT_FLAG=Y&make=MBZ&Context_make=&please_wait=N&LastVisited_input=&Previous_Section=&forumid=&threadid=&command=DWsearch&description=mercedes+rtv&I1.x=0&I1.y =0- Nick at Pelican Parts
 
Richard Comments: The Mercedes garage wanted to do it for me - the sweethearts were happy to quote the bargain price of £412... I wonder how much RTV that buys?
May 19, 2016
  Followup from the Pelican Staff: A lot? - Nick at Pelican Parts  
shemechanic Comments: Is it typical for the engine to have a rough start after doing this job?
November 9, 2015
  Followup from the Pelican Staff: No. Is the check engine light on? Sounds like an engine misfire. I would check spark, fuel and compression on all cylinders.
- Nick at Pelican Parts
 
Marcelo Comments: Any update for the RTV either curil-t or Disko HT? Or something else?
October 17, 2015
  Followup from the Pelican Staff: Stick with a high temp black RTV. - Nick at Pelican Parts  
Phuong Comments: I used Curil T on the breathers, waited a day to drive the car and it leaked every where. Do you know why?
January 20, 2015
  Followup from the Pelican Staff: Try using a standard RTV. - Nick at Pelican Parts  
fernmc Comments: Curil-T is not for the MB breather cover. Curil-T max fillable gap joint is 0.1mm which is much less than the type male-female joint used in this breather. Maybe Dirko HT but I would rather do not guess. I used Curil-T as suggested in this article and had to redo the job in one day. When I reopen the joint most Curil-T had gone. It was burned or dissolved in the motor oil. The right sealant for this application is from Mercedes Benz and does not cost more.
January 15, 2015
  Followup from the Pelican Staff: I will have someone confirm this and have the article updated. - Nick at Pelican Parts  
rami Comments: I have an in/lb torque wrench. What would be the torque specifications for the valve cover and breather cover bolts? Thanks
October 13, 2014
  Followup from the Pelican Staff: I dont have those specs handy.

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
 
rami Comments: Hi I have a 2003 Mercedes w203 exactly like the one in your picture. I have a question about the crank case breather hoses that you are supposed to remove before you remove the valve cover. Where and how would reattach the new hose? Where would I get the hoses from? Is it easy to replace the hoses or track where they are coming from? Thanks.
September 28, 2014
  Followup from the Pelican Staff: They are detached from the valve cover when replacing. You can replace with new if they are worn. Give our parts specialists a call at 1-888-280-7799. They can help you find the right part.
- Nick at Pelican Parts
 
ray Comments: What is the size of the longer E10 torx bolts? The ones I am referring to are the long ones on the left side that both hold the breather cover to the valve cover and hold the valve cover to the head. Also, I broke one of those, how can I remove the part still stuck? Thanks
July 3, 2014
  Followup from the Pelican Staff: Do you mean thread pitch and length? To remove the broken bolt, try drilling a hole, then removing with an extractor. - Nick at Pelican Parts  
philosophico Comments: What if the breather covers don't want to come off as if they are frozen on and won't wiggle off?
June 16, 2014
  Followup from the Pelican Staff: You may have left a fastener on the engine. If not, try gently tapping the cover with a soft-faced hammer. - Nick at Pelican Parts  
jglenn Comments: Can I purchase the valve cover breather gaskets for right and left side from anywhere? I have an oil leak by the oil filler part of the valve cover breather. Just trying not to have to purchase an entire valve cover.
March 5, 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
 
Boxster Comments: What is the torque spec for both valve cover bolt and breather cover bolt?
December 17, 2013
  Followup from the Pelican Staff: 8mm bolts: 18 ft-lbs
6mm bolts: 89 in-lbs- Nick at Pelican Parts
 
Linda Comments: Thanks whunter. I have a 1992 300D 2.5 L Turbo diesel. Engine 602.962; W124 chassis. Do you have any pictorials on valve adjustment and also looking at the breather hose gasket replacement tutorial or pictorial. Thanks so much! Linda
July 15, 2013
  Followup from the Pelican Staff: These are hydraulic valve tappets (lifters), there is no adjustment.

FYI:
These units have been superseded four times on your engine too hydraulic valve lifter MB# 6010500825
http://www.pelicanparts.com/cgi-bin/ksearch/pel_search.cgi ?SUPERCAT_FLAG=Y&make=MBZ&please_wait=N&forumid=&threadid=&command=DWsearch&description=6010500825&x=10&y=7

I am not sure what breather hose gasket you are asking about.
-whunter-
 
suzanne6052@me.com Comments: Breather hose gasket replacement
July 6, 2013
  Followup from the Pelican Staff: Sorry, are you asking a question or referring to the title?
-whunter-
 

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