E420 Motor Mount Experience - PeachParts Mercedes-Benz Forum

emerydc8 · #1 05-07-2010, 07:12 AM

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.

deanyel · #2 05-07-2010, 09:26 AM

Seems to me like I saw a pro say that the 124/119s were the worst, along with the 129/119s. And the 129/120s can't be fun either. I've heard of people compressing the mount in a vice to get it to go in. You shouldn't have to do it again. Thanks for sharing.

samiam44 · #3 05-07-2010, 09:30 AM

I did mine a few months ago..

I didn't have to take the exhaust off as noted. I did take on the driver's side the airduct and side plastic panel off- near straight access to the front block bolts. The rears an extension through the wheel well @ tie-rods.
I think taking the brackets loose and out of the way really helps. I had an off-set socket thing for the top bolts- you can torque them that way too. Stahlwille or someone makes them nice at $40 but got a knock-off on ebay for $12.
It was pretty easy except the I would highly suggest anyone to power wash and degrease repeatedly the lower engine area before working on it.

If you've got the exhaust pipe out- it's a good time to replace the PS return hoses!! Check the PS pump for leaks as makes easier access of those mounting bolts too.
I think every thing I've touched on the e420- I've had to remove something else to get at it or put it back... just limited space.

Michael

emerydc8 · #4 05-07-2010, 05:38 PM

Quote:

I would highly suggest anyone to power wash and degrease repeatedly the lower engine area before working on it.

When I turned the passenger side mount upside down, it was so flattened and blown that antifreeze poured out. At first I thought I damaged a hose by lifting the engine, but it makes sense that the reservoir is directly above the mount and the antifreeze must have accumulated inside the mount over time.

It is a messy job.

92497pmu · #5 05-07-2010, 05:52 PM

Sorry man, this is one of those things I paid my guy $200 to complete on my E300. It was pouring buckets that day - About $100 each for parts, $200 labor.

I would recommend find a good mechanic to do this one.

samiam44 · #6 05-07-2010, 06:57 PM

Phil,

It's a cake walk on a 300e- darn near the easiest thing you can do.
I'd say all three mounts should run you over $125 and an hour with some basic hand tools to install.

Michael

emerydc8 · #7 05-07-2010, 10:09 PM

I wish I could say it was a cake walk on the V8. With all the technology out there, it's too bad these shop manuals don't provide any pragmatic perspective of the problems one could reasonably expect to encounter on jobs like this. It's like they are one step above the people who write the instructions for all the electronic products we buy from China.

samiam44 · #8 05-08-2010, 07:22 AM

Factory service manual instructions are quite good- sometimes there are short cuts- but you must remember they are written to the audience of knowledgeable everyday dealer mechanics.

Michael

emerydc8 · #9 05-08-2010, 07:47 AM

I know there's no substitute for experience, but I'll bet some of the MB techs have had difficulty with this job too. It's too bad they don't make a supplement to the main manual that shares their experiences and how they dealt with problems that often arise when doing a specific procedure. On the other hand, I guess that's the purpose of this forum.