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Registered 2008 Black SLK 55 AMG
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Well, I decided to attack my leaky oil breathers this weekend. I have been getting small leaks on both sides that drip down on the headers and exhaust and cause a hot oil smell in the cabin sometimes. Apparently this is pretty common. There is a kit you can order from mercedessource.com that makes it MUCH easier to do this. He even gives you a really great video on how to perform this yourself. I would say on a scale of difficulty this would be about a 3 out of 10. Really the only hard part at all is trying to squeeze the gasket sealer out of the stupid tube. It is REALLY hard to squeeze. I think warming it up in some hot water first would have helped a lot. You will need some plastic razor blades, a stiff non-wire brush, some mineral spirits and hot soapy water to complete this, as well as various sockets and a torque wrench.

Here are the steps after you remove the engine cover and air box:
1. Remove the back 2 coil packs on the passenger side and all 4 coil packs on the driver side. Just squeeze each plug until it clicks and it will come out easy. I had to clip the two zip ties on the driver side to get the coil pack wires out of the way.

2. Pull the breather hose off of the passenger side. If this hose is brittle you will want to have a new set on hand. The full set is only $20

3. Take out the two long bolts and 2 short bolts on the passenger side breather. Then use a soft faced mallet or hammer with a piece of wood to tap the cover a bit to loosen it. I then used a little pry bar under the nipple for the breather hose to gently pry it up. DO NOT pry under any part of the edge of the lid! It doesn't take much force to get it loose.

4. Do the same process on the driver side. There should be 3 small bolts and 4 of the long bolts. I couldn't get the breather hoses off that side so I took the breather lid off first, then detached the two hoses. To pry, use the little post that holds the rubber piece that your engine cover snaps down to.

5. Cleaning part 1- Use a plastic razor blade (NOTHING METAL) to work around the groove in the lid to remove all of the old sealant. This will take a good 20-30 minutes to ensure you have it all pulled out of there. Once the majority of it is out then you can use a stiff brush (try curring a paintbrush down to about 1.5 inches) and some mineral spirits to clean it all up. Work the brush in the groove with the mineral spirits until it looks nice and clean. Make sure to clean around each bolt hole. I had to use a toothpick to clean the little bolt holes. Repeat this on both lids.

6. Cleaning part 2- Use hot (as hot as you can work with) soapy water to clean the lids thoroughly. This helps to clean out all the remaining oil from the pores of the metal. Once this is done hand dry the lids and then put them in the oven at 200 degrees until they are nice and dry. You don't want any moisture left when you use the sealant.

7. Cleaning the engine- You will use the same 2 step process to clean the engine side of the breathers. Be VERY VERY careful not to drop stuff down into the engine. I put rags in the bigger holes that looked right down into the engine and then used a vacuum right next to my plastic razor blade as I carefully took the sealant off of the top of the valve cover. Once you get all of the sealant off the lip, then use a rough cotton rag or non-scratching cleaning pad with some mineral spirits to clean the edge that mates with the lid. Clean this several times to ensure it is really squeaky clean. You can then use a water and soap mixture to complete the second cleaning and even some alcohol or more mineral spirits for the final wipe off before the sealant goes back on.

8. Once you are convinced everything is perfectly clean then you can put the sealant you purchased into a bowl of hot water to heat it up. I didn't do this and it was REALLY REALLY hard to get it to come out of the tube. I seriously had to use every bit of force I had. You want to cut about a 1/16 inch hole in the end of the sealant so it fits nicely in the groove on the lids. Make sure all of your tools are ready as the sealant sets up relatively fast (5-10 minutes). You will need a torque wrench. The small bolts are torqued to 4 newton meters the large bolts are torqued FIRST to 4 newton meters then fully to 8 newton meters. YOU CANNOT REUSE THE SMALL ALUMINUM BOLTS. You need to buy new ones. If you order the kit that comes with everything from that website above, he supplies new bolts.

9. Fill the lid groove with sealant until it is just slightly, slightly higher than the side walls of the groove. You don't want too much and you don't want too little. Make sure you get all of the groves that run in the middle of the lids and seal around all of the bolt holes. Then once you are satisfied with this take your lid over to the car and place it where it goes. Attach the small bolts first and torque to 4Nm. Then put a little sealant under the washer for the long bolts (don't forget to clean the old off) and torque them down first to 4Nm then again to 8Nm. You should see about 1/16th of an inch of sealant ooze out all around the lid. DON'T WIPE ANY EXCESS OFF or you risk pulling it out of the groove.

10. Let your car sit for at least 24 hours to fully dry. Then put everything back together and you should be good to go. After everything is dry, I did use some carb cleaner to clean off where the oil leaked onto the engine and especially where it dripped onto the headers and exhaust. This dripping on the exhaust is what was giving me a hot oil smell in the cabin.

Overall about a 4 hour project. A dealer would charge you an arm and a leg for this and wouldn't take the time to really clean the parts well. The cleaner the parts are, the less likely it will fail in the future. I would get the kit I bought because the sealant and bolts at the dealer are only a couple of bucks cheaper than the whole kit with the cleaning supplies, sealant and bolts.
 

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