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Oil Seepage from Cam Expansion Plugs

29K views 44 replies 26 participants last post by  Avel Du 
#1 ·
Date: May 27, 2009
Order No.: S-B-01.30/23b
Supersedes: S-B-01.30/23a dated May 7, 2009

Group: 01

SUBJECT:
All Passenger and Light Truck Models, Equipped with Engine M272 / 273
Up to approx. June 2008 Production
Oil Seepage from Back of Cylinder Head

If you receive customer reports in the above model vehicles of oil seeping from the engine, the cause could be the round plastic expansion plugs on the back of the cylinder heads.

To resolve, perform the following.
  1. Remove air filter housing. For Models 164 and 251, refer to WIS document AR09.10-P-1150GZA.
  2. Remove the existing plugs, clean the opening and install new plugs.

Note:
The plug opening should free of grease or oil. No sealer should be used in the installation of the new plugs. There are two different size plugs as listed below.
- A000 998 55 90 - 2 small expansion plugs
- A000 998 56 90 - 1 large expansion plug (engines without vacuum pump)



Picture source
 
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#5 ·
Just went to my local benz dealership today and got the replacement plugs.

Each small plug was $7.96 CAN and the large plug was $13.26 CAN, $30 in total once you factor in tax.

If your car has not had this done or you are not sure I would recommend doing this. Very cost effective and an easy DIY. Could even do the air filters while you have the air box off.
 
#6 ·
Thanks v much for this useful thread!

I believe my slk is leaking as well and I sure hope it is the same issue as is identified here with this simple fix.

I noticed in another thread a user suggested to put some oil around the seal before inserting the replacement gasket... and in this thread it was mentioned the following:

Note:
The plug opening should free of grease or oil. No sealer should be used in the installation of the new plugs


Should I use some oil to help it seal better or just plug it in? Thoughts? Suggestions?

Thanks!
Sushi
 
#8 ·
Great thanks! That's what I did too - didn't seal just replaced it directly.

Comparing the old and the new expansion plugs - of course it looks identical - but I don't feel/see any difference between them. I would've thought the old one is much harder therefore causing the leak due to low flexibility (if that makes sense). With the plastic toughening up it doesn't seal as good and therefore causing the leaks - is this the reason why it was leaking in the first place generally?

To me - they both seem to be the same level of hardness. Can't see any diff.

Right after replacing it - I was still seeing the white smoke and can smell burning oil. Could've been the old oil - so I washed it down. Afterwards, I don't notice any more burning oil thus far (knock on wood).
 
#10 ·
My Experience

I just replace my expansion plugs today and thought that I'd share some pictures and lessons learned. Quick and simple job that anyone can do themselves.

Materials Needed:
- New Plugs. Note, the parts counter argued with me about the need for all three plugs, but I already taken a look and saw that all I required were the 2 smaller plugs, as the TSB stated, not all require the large plug. Had to make him read that :).
- Shop Rags
- Your favorite cleaner/de-greaser. I like brake cleaner.
- Standard Screwdriver
- Mirror (Borrowed from the wife, don't tell her :))
- Tweezers (Borrowed from the wife, don't tell her :))
- Q-Tips
- Razor Blade

Remove the air breather assy.
The following pertains to either side.
- Spray some cleaner on a rag and clean the area around the plug. Do this to avoid getting grit inside of the opening when removing the old plug.
- Position the tip of the screwdriver against the old plug, and give the butt end a little bump, the old plug will come right out. (First Pic)
- The next two pic's are to show the difference between the old plug (P/N A000 997 76 20) and the new plug (P/N A000 998 55 50). As you can see, there is a significant difference in the sealing area.
- The plugs area is between two matting surfaces, the head and the head cover. I'm going to surmize that during assembly, the plug was installed prior to torquing the head cover as I found that there was sealing material that oozed out and hardened, this would interfear with a flush fit when installing the new plug. I took a razor blade and scraped the surface clean (Fourth Pic). In doing so, some material fell into the opening. This problem was quickly resolved with tweezers and q-Tips.
- To install the plug, just insert and firmly push in.
 

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#16 ·
If not a recall, then only under warranty
 
#18 ·
I own a 2006 SLK 280 that leaks engine oil if its been sitting too long (over a week) without being driven. I noticed this problem primarily in the cold winter months when I don't operate the vehicle very often. Could this problem be related to the contraction of these plugs?
 
#19 · (Edited)
adgvpm,

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#22 ·
Hi Guys, I noticed an oily film on the LHS cat. so investigated. Saw that oil was dripping down from a leak from the large blanking cover. I checked all the others and no leaks were seen. I bought 1 large and 2 small covers for a total of £11.73. I removed the large one with a screwdriver blade after cleaning all round the area and checked inside the orifice with a mirror. Nothing untoward to be seen. Wiped everything clean and installed the cover pressing home firmly and evenly. I did not change out the small covers as no leaks could be seen.

Points to watch. On the cover there are sections that are slotted to make installation easier. I marked the old one before removal and orientated the new one the same way. When removing the old one of the slot segments broke off but did not go inside the engine. I noted that on one the side of the cover all the segments were brittle and broke off easily but the other side was fine. So the old cover needs to be removed with care. I did not lubricate the new cover. The old cover had a lot of oil trapped in it and that ran down the back of the engine so rags should be placed under the cover.

On examination I noted the brittle segments had been on the upper side of the cover as it had been installed. Also here the rubber sealing had deteriorated and maybe caused the leak. Oil pooling may have prevented the lower side from get as hot and becoming brittle. One might say that the leak would be from the bottom but this may not necessarily be so. I also noted the new cover had a different part number and appeared to have a slightly different profile.

So, not a difficult job or indeed expensive and I can see no reason for the cover to leak again anytime soon. A long run I hope will confirm this. I believe all these seals will fail eventually so will need replacing. MB used a cost effective method the close the orifices and my covers lasted at least 60000 miles so not complaining.:grin:
 
#23 ·
I've had my SLK a week. I have noticed that after I drive up a very steep hill (such as my driveway), that when I park, I smell a slight smell of burning oil on something hot, like the exhaust system. I do not smell it any other time, and I've been paying attention after first noticing it. It is consistent that I smell it after driving up my driveway, every time.

If I immediately open the hood, I do not smell it in the engine compartment. Also, there is no sign of oil dripping on the garage floor.

My first thought is that it's the car telling me not to park him, that I need to be driving. I guess that's possible, but in case that's not the reason, I wonder if this plug TSB could be the problem?

I'll be getting in there and taking a look at these plugs ASAP.


Garret
 
#24 ·
Hi Scott, the oil drips on to the catayser and smokes. I bought 2 small caps and 1 large cap or cover. Only used the large one. Easy job and the parts are cheap. Just take care when removing the old items as they may be brittle and crumbly. if you take off the undertray you'll find oil in there too. If the cover or covers are leaking, well that's where that oil probably came from too. It's Monday, all the parts dept's will be open so get on it!:wink:
 
#25 ·
So i opened up my hood and noticed a white smoke coming from the passenger side. I looked closely and found out that some oil drips in the exhaust. Ive attached some photos of where i think the leaks is coming from but i could be wrong.
Could it be the valve cover? Or the small and large caps?
 

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#32 ·
Been smelling oil and feared the worst. Investigated, identified plugs as culprits. Searched this forum and BICKETY-BAM my fears were put to rest. Now to order those puppies.....
I'm left to wonder what purpose these "expansion" plugs serve. The name implies that they might expand under increased pressure, perhaps to avoid damage elsewhere. I remember my uncle telling me "you can't have too much oil pressure" but that didn't make sense then and it doesn't make sense now. Any comments?

Btw thanks to all who take the time to write about and elaborate on these issues. It has really helped relieve some of the anxiety out of owning this beast of a car. I'd like to buy you all a Coke to show my appreciation.
 
#34 · (Edited)
just replaced mine over the weekend

kinda surprised how much oil leak out from there... >_<;;

just to clear things up regarding 1 x Large cap and 2 x small caps

i spoke with dealer and sort this out.

Large cap are for R171 without vacuum pump. (applies to SLK 350 & 55 AMG)??

i believe SLK 280 just needs 2 x small caps. (mine only need 2 x small caps)

SLK 350 will need large cap + 2 x small caps.

best bet is give them your VIN # and ask them if you need all 3 caps or just need 2 x small caps.

hope this helps!
 
#42 ·
Forgive me not posting actual part numbers. This first pic is the smaller plug, of which you will need two. The second pic is the larger plug. One is necessary.

I purchased these from a MB dealership. The technician I talked to said he installs them dry, with the “teeth” are aligned vertically, as opposed to horizontally.

For those researching the subject, the technician told me he replaces them routinely, about every 50,000 miles. A PITA perhaps but cheap and simple to replace.

My car is an 05 350. Cheers
 

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