I just did my motor mounts on my 1994 E420 and wanted to share some of the issues I ran into for anyone planning to do this.

I am referring to the first page of this link from the shop manual:

https://docs.google.com/fileview?id=0B-WRh0Hf7VdZMjgyZTY0MGEtZjM4My00ZjUyLTlmOWYtZTVhYTExYTVlY2M3&hl=en

1. The manual has you remove the connecting exhaust pipe running from the collector on the left bank of cylinders where it runs under the engine to the passenger side--two nuts on each end. It should have been no big deal with two 12-inch extensions and a 13 mm socket to get to the bolts at the collector--except that one of the collector bolts snapped off while I was removing it and, after about an hour, I figured out that I could hammer the head out from underneath (it's an insert) using two twelve inch extensions and a small torx socket to fit over the broken threaded part that was stuck in the collector. Mercedes was at least smart enough to realize that the bolts would eventually corrode and snap and it is virtually impossible to get to it from the top of the engine compartment. I was able to find another 3" long nut and bolt to use as a temporary fix (maybe permanent because I don't plan on doing this again).

2. The manual says to take out the mounts and carriers together by unbolting the four carrier bolts that go horizontally into the block. Right off the bat, I couldn't get to the driver's side front carrier bolts. Instead, I was lucky enough to break loose the 17 mm bolt (torques to 55 NM in diagram) that goes vertically through the mount using a swivel head, ratcheting box end wrench (and my palm as a hammer). Once I got the 17 mm bolt out, the mount was free. The new mount was not flattened (like the old mount) and it was substantially taller, so it would not fit through the same space as the old one and I had to remove that plastic foot long tube that blows intake air onto the motor mount from the front. This gave me enough space to slip the new mount in from the front.

(It could be possible that since I was using a floor jack and a 2x6 under the engine pan to lift (instead of a hoist from the top), I could not get the engine high enough without the back part of the engine damaging the firewall. I didn't want to damage any hoses or throttle linkage, so I just jacked it up to the point that there was no space between the engine and the firewall.

3. On the passenger side, I thought I'd do the same thing and just remove the 17 mm vertical bolt instead of the four engine carrier bolts; but as Deanyel warned me a few days ago, the ratchet wrench kept slipping off the bolt head. I tried wedging a piece of 3" long 2x2 between the block and the head of the bolt, but this just wasn't going to happen. Luckily, I was able to reach all four carrier bolts really easily on that side with a 3/8" ratchet and a 15 mm (I think) socket. Once I got the carrier loose, there was no way to fit the mount and carrier out through the hole in the bottom, so I maneuvered the mount upside down and took out the 17 mm bolt. This separated the mount from the carrier and gave me enough room to get them out. BTW, on both mounts, I reinstalled the carriers before reinstalling the mount and running the 17 mm bolt through the top.


4. It took some work to get the two bottom mount bolts (13 mm) to line up with the holes. I lowered the engine gradually until there was enough thread in the mounts to catch with the bolts. With the 17 mm bolt loosely installed you can move the mount around to see the holes for the bottom mount bolts. Once both lower bolts on each mount were loosely threaded, I lowered the engine the rest of the way and tightened the 17 mm bolts as hard as I could with the ratchet wrench, but there's no way to get a torque wrench on those vertical bolts with the mounts installed. The bolt heads angle in towards the block.

5. I was able to do everything from underneath the car. I did double check that the locking anti-rotation tabs were correctly positioned from the top of the engine compartment before snugging down the 17 mm mount bolts. They are easy to see from the top.

It took a total of 7 hours of walking on my shoulder blades and this included about 45 minutes for the transmission mount. It's not something I look forward to doing again.

__________________
1993 400E, 256,000 miles (totaled)
1994 E420, 200,000+ miles
1995 E420, 201,000 miles