Motor Mounts, 300D

Hi

Bought new motor mounts the other day, so I started working on it today,

I took the 10mm nut off the shock, took the 2 10mm bolts off the shock cover on top, took out 1 6mm allen screw, but cannot get to the one in the back, how do i do this? also does anyone have any other pointers for me?

John

[JimSmith]

Turbodiesel,

I recently asked this question and got some good guidance. You should do a search for motor mounts. But I ran into the same problem and posted my results. I found the little plate on top of the rubber element and under the structural strut extending from the motor block interfered with getting the Allen wrench into the socket head capscrews (6 mm) that go in from the top. The way I got this plate off in the end, was to remove the 8mm socket head capscrew (one from the bottom) entirely. Then I jacked up the engine about an inch or more, on that side only (this was only a real problem on a 240D, which I did, on the driver's side). When I got the engine high enough ( I used a hydraulic jack, with a couple pieces of 2x4 between it and the oil pan), I could pull the little plate out. You can actually move it far enough around to move it out of the way so you can get the Allen wrench into the socket head capscrew. Once out I could get the Allen wrench on the fastener, but it was still kind of slow going as the area available to turn the screw with the wrench was limited. You need to do the same in reverse. Once the engine is up pretty high, I could not put the new mount in position and then slide the plate back into its position because (you will see this when removing the old mount) the strut coming from the engine has a protrusion that goes into a depression in the plate and mount that is a little deeper than I could raise the engine. The answer was to slide the plate and the mount in position together, then rotate the plate out of position and get the screws that go in from the top (the 6mm ones), then lower the engine to get the 8 mm one from the bottom started, jack the engine back up and rotate the plate out of position and finish tightening the 6mm capscrews. Then drop the engine again and finish the 8mm one. I also found I had to replace the snubber mount on the bell housing flange that mounts to a cross member at the bottom of the engine as the thing was kind of dissolved by the collection of oil leaks dripping on it and then the squeezing it got when I jacked the engine around. The first mount took quite a while, and I recommend an 8mm hex bar and socket wrench to make the capscrew that goes in from the bottom easier. On the passenger side of the engine I could get the two 6mm capscrews out with a similar wrench. In the end the driver side took a few hours the passenger side took 20 minutes.

I hope this helps and do a search to find the other recent threads on this subject. Good Luck, Jim

[psfred]

John:

123 motor mounts -- just like 115 motor mounts, one allen is UNDER the arm from the engine, right?

When I changed the mounts in the 220D, I think I used a standard 6mm rigth angle allen wrench. There is no way to use a ratchet.

Jack the engine up as far as you dare and fish around with the short end of the allen wrench -- you may have to grind or cut off part of it to get it in there. Do not put any fingers between the arm and the mount at any time, please!

New one goes in the same way -- by braille. Why MB didn't rotate it 90 degrees is beyond me!

The alternative is to remove the "arm", which I don't recommed unless you have an engine hoist.

Since this is an MB, the bolt won't be hard to get out when you finally get the wrench in it. I've not found a stuck bolt or screw yet, with the single excpetion of a corroded sheet metal screw on my brothers 75 300D!

Peter

What have I gotten myself into??

Thanks for the advise, I'll try again tommorow.

John

[Zoonhollis]

Turbo,

I just changed the mounts on my 300D the other day, and found that the passenger side was much easier, as Jim mentions. However, I think you will be able to use a socket on the two OUTSIDE 6mm fasteners from above (with several extensions on the ratchet and a U-joint), but you must use an "L" wrench to get to the inside ones, and the driver's side is particularly knotty. I had to grind down the short end of the wrench a little to get it in such a tight spot. Be warned also if you begin to strip the 6mm hex head a little with the wrench, since you are unable to see what you're doing. This happened to me, so I used a bit of sand on the end of the wrench to make the fit snug again.

[JimSmith]

John,

Don't be intimidated as the job is tedious but not rocket science. Getting the old mounts out is probably 85% of the job as you will find out all about making access for the Allen wrenches and how the parts come out. Installation is pretty much the reverse, except I had to thread the bolt that comes in from the bottom (8mm on a W123 240D) a few times to make sure I was not cross threading it and the mount was aligning with the hole in the subframe and the tapped hole in the engine mount strut. The socket with an 8mm hex bar turned out to be very helpful as I could get a good feel while threading capscrew into the tapped hole. The location of the turbocharger on the 300D may make the passenger side a similar challenge, but when you look at the shape of the strut that bolts to the engine, the one on the passenger side does not interfere with access to the 6mm bolts like the one on the driver's side.

I did most of the cranking on the fasteners lying on my back under the mounts, with my head propped up on the tire. With the offending plate out of the way, I could actually position myself to see part of the inboard 6mm capscrew. It was a help to get a visual aid (a strategically place mirror might also help with this) to engage the capscrew socket with the Allen wrench.

I got really greasy and oily. But that is because my car has an oil leak at the rear crank seal and the breather tube connection to the intake manifold. Consequently there is a lot of nasty stuff all over the area of the bottom of the engine.

I started by putting the car up on ramps, and then raising the hood to the 90 degree position to get the best light and access. The rest was normal cranking and yanking, with a typical measure of persistence required to do any such jobs. I would love to see the access improved for that inboard screw, but this is a once every 200,000 plus miles type of job so if there is one that must be tough to get to, I guess this is not a bad choice. If I did it again I think the whole thing could be over in an hour and a half. It took me that long to get the black goo off my arms and hands (and knees and face and the rest of my body).

Best of all the change made a big difference in the behaviour of the motor when the car runs and starts. My driver's side mount was broken in half so the starter would try to lift the engine up as it cranked. This slowed the cranking speed during the compression stroke a lot, and the car became very hard if not impossible to start (since it is a 4 speed manual, it could always be push started though). The broken mount and all the banging around and extended cranking attemptng to start also contributed to damaging the starter. While I was under there I changed the starter as it failed completely just before I bought the mounts. I got a great deal for the starter from FastLane. The car now starts right up and runs very smoothly. The satisfaction of fixing the machine and having it run smoothly more than makes up for the struggling and getting greasy. Jim

[JimSmith]

John,

Sorry to be answering this so inefficiently but moving the little galvanized steel plate on the top of the rubber mount once you remove the 8mm capscrew that comes in from the bottom and you jack the engine up (with this bolt out, the mount is now only bolted to the subframe of the car, and when you jack the engine up the strut from the engine will separate and move upward with the engine) is still not easy. It may be stuck in the rubber of the mount, or it may be a little wedged between the strut and the mount. But it can be loosened. Once it is loosened the cutting of the "L" shaped Allen wrench is not required as you have pretty good access. You still have limited angular stroke on the screw, so settle in for a while of turning less than a quarter turn at a time. My fasteners were not overly tight to break loose, but they did not run freely until the last few turns (meaning I could not use only my fingers until the fasteners were nearly all the way out). Jim

[JimSmith]

John,

Don't be intimidated as the job is tedious but not rocket science. Getting the old mounts out is probably 85% of the job as you will find out all about making access for the Allen wrenches and how the parts come out. Installation is pretty much the reverse, except I had to thread the bolt that comes in from the bottom (8mm on a W123 240D) a few times to make sure I was not cross threading it and the mount was aligning with the hole in the subframe and the tapped hole in the engine mount strut. The socket with an 8mm hex bar turned out to be very helpful as I could get a good feel while threading capscrew into the tapped hole. The location of the turbocharger on the 300D may make the passenger side a similar challenge, but when you look at the shape of the strut that bolts to the engine, the one on the passenger side does not interfere with access to the 6mm bolts like the one on the driver's side.

I did most of the cranking on the fasteners lying on my back under the mounts, with my head propped up on the tire. With the offending plate out of the way, I could actually position myself to see part of the inboard 6mm capscrew. It was a help to get a visual aid (a strategically place mirror might also help with this) to engage the capscrew socket with the Allen wrench.

I got really greasy and oily. But that is because my car has an oil leak at the rear crank seal and the breather tube connection to the intake manifold. Consequently there is a lot of nasty stuff all over the area of the bottom of the engine.

I started by putting the car up on ramps, and then raising the hood to the 90 degree position to get the best light and access. The rest was normal cranking and yanking, with a typical measure of persistence required to do any such jobs. I would love to see the access improved for that inboard screw, but this is a once every 200,000 plus miles type of job so if there is one that must be tough to get to, I guess this is not a bad choice. If I did it again I think the whole thing could be over in an hour and a half. It took me that long to get the black goo off my arms and hands (and knees and face and the rest of my body).

Best of all the change made a big difference in the behaviour of the motor when the car runs and starts. My driver's side mount was broken in half so the starter would try to lift the engine up as it cranked. This slowed the cranking speed during the compression stroke a lot, and the car became very hard if not impossible to start (since it is a 4 speed manual, it could always be push started though). The broken mount and all the banging around and extended cranking attemptng to start also contributed to damaging the starter. While I was under there I changed the starter as it failed completely just before I bought the mounts. I got a great deal for the starter from FastLane. The car now starts right up and runs very smoothly. The satisfaction of fixing the machine and having it run smoothly more than makes up for the struggling and getting greasy. Jim

Its quite alright, I really appreciate all the help, I will post tommorow if I have any questions or (hopefully) if im done.

Thank you very much!

John