Front brake rotor stuck on hub
 

Have a 1987 300e with a front disc that won't budge. I've taken the caliper off and removed the set screw with no problems and thought a few hits with the rubber hammer would set her free. No way no how even after applying heat and wd40. I noticed two metal hollow pins with a cutout that travel through the disc into the hub. I assumed these are for centering but I really don't know. I've searched the threads and found quite a few problems with rear discs that were solved with the use of a bigger hammer. Is this my fate also? I really don't like breaking things, usually ends badly.

Yep, bigger hammer. (If equipped, make sure you removed the allen head that mounts the rotor to the hub). The rubber mallet is taking the blow vs. the disc. You can (if you want) use a punch and push the pins through - but usually isn't necessary. When hammering I like to hit the edge of the rotor hard to help break and rust then I go around the perimeter on the face of the rotor...I then hit once or twice from the inward facing face and it comes loose. Usually it doesn't take that much.

Thanks I'll give it a go tomorrow morning.

Stuck Rotor
 

Well obviously you're at the point of replacement now; so 5lb sledge hammer it (them) off! Rotate as you bang away!! Be certain to wire wheel off all of the corrosion on the hub surface & apply anti-seize before installing the new set. Check your calipher piston seals for leaks. Also, observe if the wear pattern is even on the pads. If not, the master cylinder may not be delivering even pressure through the system! Change out completely the old fluid & use DOT4! See the link provided:

http://mb.auto.pl/index.php/Dok.-serwisowa-CD2.html

Hitting the rotor with a torch for a couple minutes prior to hitting it can help it come right off.

I had one rotor that, with all the suggestions above, just wouldn't come off. I put a large gear puller on it, pushing against the axle stub after removing the sheet metal cap. I didn't pull it off with the gear puller, just set up a decent amount of pull, then whanged away with a 2-pound hammer on the outside edge of the rotor. It finally popped loose and came off by hand.

toomanycars, install one lug bolt by a few threads before hitting the rotor with a sledge hammer. The lug bolt will restrain the rotor when it lets loose. Light wire brushing and applying some rust cutter at the hub/rotor joint usually helps the removal process.

Castrol Olistamoly 2 is the stuff Mercedes recommends for coating the hub->rotor contact surface. Mercedes part number is 000 989 63 51

Rubber hammers don't free rotors, and usually neither do claw hammers. You need a small metal sledge (no less than 4lb) and some aim. You're trying to vibrate the rust & brake dust out of the mating surfaces, which is why it has to be (heavy) metal-on-metal action.

If you smack the back of the rotor, you risk damaging the wheel bearing, stressing the tie rods, etc... and actually warping the rotor so that the center part clamps on the hub even harder.

Drench everything with your favorite penetrating oil (pb blaster, deep creep, etc...), let it sit for a few hours, than bang between the fastener holes in a star pattern like you're trying to hit a home run.

Sometimes it takes a few whacks, sometimes it takes 2 people an hour or more.

Thanks for all the great suggestions. I decided to punch the two sleeve centering pins through the rotor before giving it a whack. Unable to find my hand sledge I used my splitting mall [the fat side] with short swings to the rotor as it spun around. The rotor finally broke free and I felt so good about that I did the other side. More heat and penetrating oil and a lot of stress filled swings with the maul finished the other side. I spent the rest of the day installing new rotors and brake pads. Hopefully I didn't break anything in the suspension and I will check the wheel bearings. I'm not looking forward to doing the back brakes.

I found the back brakes to actually be easier than the fronts (on my W140 at least). Hopefully, it will be the same for you.

I just went through this yesterday while replacing the discs on my w203. Took a lot of pounding and liberal use of penetrating degreaser. My buddy and I had to take turns wacking away at the thing. We used a standard hammer, so it probably would've been easier with a heavier hammer. Glad to hear I'm not the only one dealing with fused discs/hubs. The wheels themselves can also fuse to the discs.