Replaced the Engine and trans mounts a week ago and all the vibration is gone.
The only vibration (if its vibration) that I now feel is in neutral or parking gear when the rpm goes up to right around 750, where as in brake mode while in reverse or drive gear it is right around 550 and there is no vibration at all. I'll keep a watch and start a new thread for it. My next project for this car is replacing the AC compressor for which I will start a new thread after doing some research.
Anyway let me share with you how the mounts were replaced in my car -
1) Got hold of the MB replacement instruction for my car. Made sure I understood every word in the one-page instruction set plus some related instructions.
2) Asked for help on this wonderful forum where as you can see so many jumped in to help and encourage me.
3) Inspected the car from the top and bottom - several times until everything made sense to me.
4) Decided not to mess with the drag link per MB instruction, as that may entail additional cost of alignment at the shop. Instead will try wiggling the mounts out and in first and if that doesn't work, will move the AC compressor and/or the alternator. Also decided 2 men best for the job.
5) Got the 16mm Mercedes offset wrench (like El Paso Tools on ebay), 3/8th long and short ratchet extensions, a low profile 16mm or 5/8" hex socket head set with 3/8th drive (like OEM Tools), a thin profile 3/8th ratchet driver (like Harbor Freight 67993) for the MM top bolts. Wrench and sockets as needed for bottom bolts, trans mount bolts, the AC compressor, alternator, ground wire nuts, battery, washer reservoir, fan belt tensioner, protective glasses, plenty of rags and plastic containers to catch the hydraulic oil if it spills. Of course floor jack, jack stands and chocks.
6) Parts - got Mercedes genuine online from www.mercedesbenzpartscenter.com
but others can be cheaper sometimes like www.mbpartsworld.com
. Don't forget to check autohausaz and others too, you never know who's running a special! Genuine is made by BOGE and very good OEM is made by Lemforder. Both are owned by ZF Auto. My old ones don't have any manuf marking, just Merc Star and part number as part of the rubber mold. The old trans mount has no markings, the new one also does not have any manuf marking just part # and Made In India label. Depending on the condition of your car, you may want to keep new nuts and bolts with you just in case. Getting it from the dealership is very expensive about $60, so I went to the dealership with calipers, measured all of em, took pics especially the manuf symbol on em and spent days trying to get exact match from places like Metric & Multistandard, Fastenal, local manufs. I couldn't find a match for the lower bolts. However, I ended up not needing any, my original bolts were all like new. So I returned all of 'em after the job.
7) Jacked up the car. Did the ds first. Unbolted and got the washer reservoir out of the way. Loosened the top bolt first with the Mercedes 16mm offset tool and ratchet extension from the top. Two 1" turns is all it takes, then you can unscrew with your fingers. Then raised the engine and unbolted the bottom bolt. Noticed hydraulic fluid, so wrapped it in a rag. When wiggling out failed, unbolted and moved AC compressor and ground wire, which allowed the mount to be brought more to the front and then was picked up from the top by the other guy. The new one went in the same way but the engine had to be raised a bit more. Hand tightened the bolt below, lowered the engine slightly, made sure the notch and the tooth were in line and dropped the engine slowly all the way. Hand tightened the top bolt from the top, then used the low profile 16mm socket head with thin profile 3/8th driver from below to approximate the 55Nm torque. This side took 2 hrs and I drove it about 20 miles to see if it made any difference but no difference.
8) Next day, we did the ps. Jacked up the car again and took off the air filter box and attached connectors. Saw no space to position the ratchet extension. So disconnected battery -ve and unbolted the two bolts on the alternator, top and bottom, eased it out of the hold and moved it to the front. This allowed me to angle my drive extension to loosen the top bolt in two short sweeps and then unscrewed it by hand. I noticed the hydraulic fluid on this. Raised the engine, loosened the bottom bolt, unscrewed it, and immediately wrapped it in a rag. This one came out easily. The new one went in with the same way, followed the same process as for the ds, and then bolted back the alternator. BTW, moving the alternator and putting it back on was no problem at all on my car. It was easier and a lot quicker than the AC compressor. This side took 1 hr.
9) Immediately after this, we did the trans mount. The one on the car was still in perfect condition, but I replaced it with the new one. This one was quick and easy and took about 15 minutes.
10) Last, we cleaned up and reconnected the battery, reset the radio code and normalized the power windows and sunroof and that was the end. Took it for a spin and that's when noticed the immediate huge improvement. I recommend anybody experiencing vibration, do the mount test and check if the mounts are leaking hydraulic fluid and replace the mounts asap. Just to let you know, my old mounts failed the test, were leaking, but still are in great shape! In terms of difficulty, I would rate it 2.5 out of 10 if at all and not to much fiddling around, at least not in my 99 C280.
Thanks a lot guys!