JCD-

When I replaced the oil filter housing gasket I also had to replace the gasket (on the housing) where the oil pressure line connects to the housing. So I really replaced two gaskets.

This job isn't too bad....but I did it on the 240...not the 300. I'm not sure if space is a porblem with the 300s.

Anyway, drain the oil and remove the oil filter. Then begin by breaking loose the 5 allen head bolts that attach the oil filter to the block. You should be able to get the upper two bolts from the top and the other three from the bottom. All the bolts are the same length except for one (it kinda goes through the center of the oil filter housing to the block). This "center" bolt is longer and I had to file down one of my allen head wrenches with a grinder as I kept butting up against the engine mount or some other bracket and didn't have enough room to get the wrench on the head of the bolt in a square fashion. If you grind one down....make sure you "cool" the wrench as you grind (in a cup of water) so that the wrench does not lose its temper. Sometimes, when a person heats something up (like a wrench to bend it or to shorten it) the metal can get so hot that it looses its temper and is not as strong. If that happens....you will break it when you apply a significant amount of stress to it.

What ever you do, make sure that the allen wrench is on the bolt all the way before you try to break the bolts. The five bolts on my car were almost "welded" on and I had to be VERY careful that I didn't round off the bolt heads trying to take them off. One bolt was on there really really really tight and I was afraid I was going to break or round it off if I just didn't quit while I was ahead. But, I just made sure that my wrench was on there all the way and I kept at it until it broke free. As I said before, make sure the wrench in on there good and also use a quality wrench.

Once you get the 5 bolts broke, you should unscrew the black oil pressure line where it connects to the filter housing. I used an open-ended wrench to break that connection. Then use another open-ended wrench to break the two oil lines that go to the oil cooler. Once I broke those two lines, I loosened the brackets that holds the lines in place so I could move the lines out of the way. Part of these lines are made out of metal and don't want to move out of your way very well....that is why you have to loosen up the brakets that hold them in place.

Now you can take out the bolts (the bolt that is the longest and goes through the oil filter housing comes out with the filter housing itself as there is NO room to withdraw the bolt while the housing is on the engine.

Once you get that done you can take the housing off. It might be "stuck" a little....just wiggle it and it will come loose.

Take a gasket scaper and scrape the gasket material off the housing (be very careful not to put any gouges in the metal where the new gasket is supposed to go. Take some fine sandpaper and sand the residue off the sureface so that you have a nice and smooth sureface to put your new gasket. I used a very small block of wood with the sandpaper to keep the gasket surface smooth and to prevent myself from sanding a "hole" or "valley" or....you know what I mean......you want the surface where you attach the gasket to be smooth and even. If you are replacing the oil pressure line gasket on the oil filter housing you should replace this before you put it on the engine.
Before you put the housing back on the engine, wash the filter housing out with mineral spirits (paint thinner) to clean it out good. You don't want to leave any old gasket material in there. Now you need to clean the engine block where the old gasket attached. Use the same method you used on the housing itself except I took a clean LINT FREE cloth and gently stuffed the holes where the oil passages are to prevent gasket material from getting into the oil passages while I worked on that surface. Don't stuff the material in the oil passages too far....you want to be able to get them back out. Once I was done, I took some Q-tips and gently swabbed the inside of these passages to make sure I didn't leave any foreign matter in there. I really took my time during this stage to make sure that I didn't get any crap into the engine. This could be bad news if you do. Also, don't be too ruff with the Q-tips if you decide to use them...they can fuzz up and you can lose some of the cotton in there if you aren't careful. The main thing is to not leave any crap in the oil passages.

Some people will disagree with me on this....but I don't care. I used (and I suggest you do to) permatex aviation gasket crap on both of the gaskets I replaced. I wouldn't use a gasket maker material like the old RTV blue crap.....but this stuff is not like the others and won't squeeze out if you use a reasonable amount when you put things back together. Some say that you run the risk of having that stuff clog up the oil passages. Well, I doubt that Mercedes put these gaskets on dry and I didn't want to do the job over again. Know what I mean? Just be reasonable when applying the stuff and you will be fine.

The Aviation gasket sealer isn't fast drying so you don't have to run around like your pants are on fire to get the housing back on. Just put the sealer on and have someone help you (a helper from above and your from below to guide the housing back in place. I put all five bolts in the housing holes before I tried to put it back on so I could use the bolts and bolt holes to help guide with the proper placement of the housing. Whatever you do, make sure the longer bolt is on the housing before you begin to put it back on....it won't go in its hole once the housing has been put back in place.

I waited one whole day before I started the car up. Permatex doesn't say anything about waiting....but I thought it would be best to give the stuff time to set up.

I hope this helps you with the project. As I said before, this was my only oil leak on the car. I wish it had taken car of the oil consumption.

Good Luck!

mike