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Engine Mount and Shock Replacement
 
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Pelican Technical Article:

Engine Mount and Shock Replacement

Steve Vernon

Time:

1-4 hours

Tab:

$10 to $200

Talent:

**

Tools:

8mm, 7mm Allen, 10mm, 7mm wrench, floor jack, piece of wood to cover the oil pan, cleaner

Applicable Models:

Mercedes-Benz W123 (1977-85)

Parts Required:

Mounts, shocks, bushing kit as needed

Hot Tip:

Make sure the Allen keys are well seated

Performance Gain:

More power to the road.

Complementary Modification:

Replace transmission mount

The engine mounts on a car are the direct mechanical connection holding the engine to the chassis. Almost all engine mounts have a rubber portion that allows a small amount of flex to reduce vibrations. If the engine was just directly bolted to the chassis, you would feel every vibration from the engine.

The rubber portion of the engine mount is particularly susceptible to failure due to the conditions of the engine bay. Heat and oil can take its toll on the mount, causing the rubber portion to crack and separate. When this happens, the mount collapses and no longer supports the engine correctly. Depending on the year of your vehicle and how it is optioned will depend on how many things you will need to move out of the way but don't plan on doing this if you need to use the car in the next hour.

A simple way to test if the mounts are failing is to have a friend sit in your car while it is running, place the car in drive and with their foot firmly on the brake pedal apply a small amount of throttle then place the vehicle in reverse and do the same procedure. If you notice the engine having any large movements your mounts are in need of replacement. The diesel motors also have shocks to help deal with the large amount of engine movements.

You need to replace engine mounts in pairs, even if only one side is bad. ONLY change one side at a time. Begin by safely lifting and supporting the vehicle; please see our article on How to Safely Lift and Support Your W123.

Over the years your car may have been serviced by multiple people including previous owners and this can lead to parts replaced with different size fasteners and hardware. The sizes of the nuts and bolts we give may be different from what you have so be prepared with different size sockets and wrenches. If something is different on your vehicle please let us know and share your info to help other users. If you have any questions or comments or even a different procedure you would like to share please leave it below and please leave your vehicle information.

There are two engine mounts: one on each side of the motor (red arrows) that hold the engine to the chassis.
Figure 1

There are two engine mounts: one on each side of the motor (red arrows) that hold the engine to the chassis. Depending on how your vehicle is optioned will determine what you will need to remove to get access to the top of the mounts. Some vehicles you will be able to remove the mount by working from below only and others you will need to come at the top hardware from the top. Both sides are replaced in the same manner.

You are going to be lifting the engine to remove the mounts so unclip the shroud from the radiator, this way as the fan lifts along with the motor it will not bind on the shroud and damage things.
Figure 2

You are going to be lifting the engine to remove the mounts so unclip the shroud from the radiator, this way as the fan lifts along with the motor it will not bind on the shroud and damage things.

It is also a good idea to disconnect the throttle linkage so you do not bend it while lifting the engine.
Figure 3

It is also a good idea to disconnect the throttle linkage so you do not bend it while lifting the engine.

With the vehicle safely lifted and supported remove the single Allen bolt (red arrow) from below that holds the mount to the engine.
Figure 4

With the vehicle safely lifted and supported remove the single Allen bolt (red arrow) from below that holds the mount to the engine. The bolt on our vehicle was an 8mm Allen but make sure of yours before trying to break it loose as you do NOT want to strip this out.

There is a good chance that the area around the mount (red arrow) and shock (yellow arrow, if your vehicle is equipped with them) is going to be very oily and dirty.
Figure 5

There is a good chance that the area around the mount (red arrow) and shock (yellow arrow, if your vehicle is equipped with them) is going to be very oily and dirty. Make sure to give this area a good cleaning including cleaning out the Allen bolts before attempting to remove the hardware.

You are going to lift the motor from below using the oil pan (red arrow).
Figure 6

You are going to lift the motor from below using the oil pan (red arrow). You are going to need to put something between your floor jack and the pan to help distribute the weight. I like to use a piece of one inch plywood slightly larger than the size of the pan, this will prevent the pan from bending and damaging the oil pick-up and pump.

After giving the area a good cleaning use a 7mm Allen; again making sure this is the right tool for your hardware and remove the two bolts that hold the mount to the chassis (red arrows).
Figure 7

After giving the area a good cleaning use a 7mm Allen; again making sure this is the right tool for your hardware and remove the two bolts that hold the mount to the chassis (red arrows). You do not need to remove the heat shield.

If you have a diesel there is a good chance your vehicle has shocks.
Figure 8

If you have a diesel there is a good chance your vehicle has shocks. The shock body (red arrow) connects to the chassis and engine by a single 10mm nut on each end (yellow arrows).

There is a small cut out in the shaft on the shock (red arrow) that you can use a 7mm wrench on to stop it from spinning while you remove and install the nuts.
Figure 9

There is a small cut out in the shaft on the shock (red arrow) that you can use a 7mm wrench on to stop it from spinning while you remove and install the nuts. Never grasp the shock with vice-grips or pliers as this can damage or destroy the shock.

While holding the shock with a 7mm wrench remove the 10mm nut on the top and bottom of the shock.
Figure 10

While holding the shock with a 7mm wrench remove the 10mm nut on the top and bottom of the shock.

If you are replacing the shocks now would also be a good time to replace the bushings, washers and install a new Nylock nut that comes with a bushing kit.
Figure 11

If you are replacing the shocks now would also be a good time to replace the bushings, washers and install a new Nylock nut that comes with a bushing kit.

Raise the motor using the jack and wood and remove the old mount and shock and install the new ones.
Figure 12

Raise the motor using the jack and wood and remove the old mount and shock and install the new ones. The mounts are the same for both sides. You can see in this photo where the 8mm bolt come through from below (red arrow) and attaches the mount to the motor and where the two 7mm Allen bolts hold the mount to the chassis (yellow arrows). Installation is the reverse of removal.

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