Engine Mount Replacement Tips

[Benz Mondi]

I just did the mounts on my 1990 300E, but this will likely applicable for most similarly configured cars. It took one hour even with some trial and error.

1. All 124's seem to share the same mount dimensions no matter what the year. This is important as some years are priced at a much higher price than others for some reason.

2. Make sure you are buying OEM equivalent mounts with hydraulic fluid filled centers. If you opt for the solid rubber ones, they are much cheaper but will likely not dampen as effectively. Know what you are paying for.

3. Release the fan shroud so that the fan blades don't snag it when you raise the engine higher than the normal opening provides. On 1990-1992, you just have to release the ring on the shroud.

4. Properly block the rear wheels and use a block of wood between the oil pan and the jack to raise the engine. Lots of tips found in this forum on how to properly jack up the car. I use ramps to elevate the front wheels.

5. Start with the driver's side first (why? will be explained below) by using an 8mm Allen head socket bit and a breaker bar to loosen and remove the bottom bolt. You access it through a hole in the frame.

6. Once you have removed the lower bolt holding the mount, raise the engine approximately 1-2". Do this slowly and check at every inch to make sure nothing is binding, especially at the rear.

7. Once you have it high enough, use some jack stands and wood blocking that will support the engine, in case your jack fails. You will now have enough clearance to get easily use both hands to use a 17mm ratchet head wrench to remove the top bolt holding the mount. Do not expose your hands and fingers to danger by putting them under anything that could come down suddenly on them if your jack and the jack stands fail.

8. Remove the top bolt and slide the new motor mount into place, aligning the tab at the top of the mount within the notch at the motor mount arm. I found it was easiest to first place the tab in the notch to help locate the hole that bolt fits into. Tighten the bolt to spec or as tight as you can without evoking super hero strength.

9. Lower the engine so that there is not more than ¼ inch space between the bottom of the mount and the frame surface that it attaches to.

10. From below slip the bottom bolt onto the 8mm allen head that is also attached to a 6” socket extension and rachet. Hold this in one hand while, with the other, use a pry bar or the handle of the breaker bar, to pry against the body of the mount and the steering knuckle so that the hole lines up in the opening enough to thread and rachet the bolt into place with the other hand. Tighten it as much as you can with one hand. Then lower the engine 1” and do a final tightening.

11. Now do the passenger side similarly. What you’ll soon find out is that the old mount on the passenger side is likely a full 1” shorter than the old driver’s side because of the torque effects on the engine. You will need to raise the engine much higher than what you did for the driver’s side because it’s the same mount used for each side. The only way that you’ll be able to raise it high enough without the rear of the engine hitting the fire wall is to force the engine to twist slightly as you raise the engine by having the driver’s side is still attached. Top bolt first (remember to install the heat shield. Re-attach the fan shroud.

That’s it. You are done! See the attached picture to see the height difference between the new one (far right), the driver’s side and the passenger side (far left).

It’s actually more simple that you think doing it this way. Just make sure to properly jack and safety block the engine, just in case your jack fails.