NOTE: I'm in the US, so driver's side is Left.
In case you don't have patience for the long post or video(skip to 5:40 for the fun part), here is the fun part (pics of new mount in the background and old mount in the foreground).
I came across some other posts detailing this issue/maintenance but I figured I would post some pictures/video of my experience too. Mainly this is to show that even if your only have a little bit of rumble/shake that you may have bad motor mounts. To save you some time, this is not an impossible DIY job, but I believe most shops will charge you the same for 1 mount and they would for all 3. In other words, get a quote first and then decide if you want to do it yourself. Doing 2/3 of the mounts yourself and then taking it a shop for the last one is a waste. Trust me.
History: Bought the car(2003 SLK 320 r170) fall 2018 with 157,000 miles - super cheap, mainly cosmetic issues. After driving it for awhile and really just pushing it I started to notice a rumble in low first gear and when shifted into reverse and first rolling. I say rumble versus shake because this was not like the shake you get at 60 mph when your alignment is out, it was more of a low physical rumble. I felt it most in the shifter knob and some in the steering wheel. The car did not violently shake or anything like that. I felt like more of a nitpick than anything for even complaining/worrying about it.
Did some searching through the forums here and on youtube and came to the conclusion that it was likely the engine and transmission mounts. There is a left and right engine mount and a single transmission mount. The transmission mount is SUPER easy and the part is cheap. If you are thinking this is your issue, start there. The engine mounts are a bit more expensive (depending on what you get). These three parts are meant to be replaced at certain intervals. I don't remember what those are off-hand, but I believe the info is in a thread here somewhere. I want to say every 60-80 thousand miles maybe.
Other posts mention looking for the fluid or stains on the outside of the mount. I didn't see this outright, but once I started working on the passenger side I managed to see, smell, and even taste a good amount of that fluid. It is a dark red color and it is not meant to leak on your face. If it leaks on your face, then you should definitely replace the mounts.
There is a pretty decent walkthrough on Pelican if you have a 230, and I believe the access to all mounts is easier on those cars. The 320 has an exhaust manifold above that makes access nearly impossible from the top. From the bottom there are components in the way (alternator, AC compressor, etc.), but you CAN work around them if need be. I am lazy and chose to try and work around them. Had I just removed the AC compressor this job probably would have gone better. The engine mounts are TIGHT, especially on the top bolt. A stubby 16mm wrench is your best friend, but to be honest these are a pain to get to. Mercedes makes a custom wrench for the job, and although I don't have one, it looked like a waste...
You need to jack the car up high enough that you can get under it, and then jack the motor/transmission up enough to relieve the compression on the mounts. I did this with a simple jack and jack stands. Then jack the motor higher once the mounts are loose so that you can pull them out. I managed to get the passenger side done (after multiple attempts) by jacking the motor WAY up and then pulling the mount forward. Be careful not to over extend hoses, etc when jacking the motor up. I would say I probably had this thing jacked a maximum of 3" in order to get the old one out. THOSE ARE ESTIMATES. I did this job about 8 months ago, so don't hold me to those. Another thread talked about only 2", but I remember thinking that was shallow when I was working on it. I needed it up high enough to pull that passenger side forward easily.
I tried and tried to get the top bolt on the drivers side, and then finally gave up and took it to a local indie shop. Paid about $400, which is what I would have paid to have them do all 3... By the time I was done, I wished I would have just let them do it from the get-go. I have seen multiple sources say that the driver's side is the worst, and multiple people end up taking it to a shop/mechanic to have the driver's side done.
For reference I used Lemfoerder mounts all around.
Pics and videos coming next.
Pelican walkthrough (pretty sure focused on 230 models): https://www.pelicanparts.com/techart...eplacement.htm
Other SLKWORLD threads: