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Pelican Technical Article:

Replacing Engine Mounts

Steve Vernon

Time:

2 hours2 hrs

Tab:

$35 to $150

Talent:

**

Tools:

17mm socket, extensions, universal joint, 17mm, 10mm wrench

Applicable Models:

Mercedes-Benz W124 (1986-95)

Parts Required:

New engine mounts

Hot Tip:

Work on a cold engine

Performance Gain:

More power to the road

Complementary Modification:

New drive belt

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. Replacement is easy and should only take around an hour per side.

You are going to need to safely lift and support the vehicle as well as remove the under engine tray. Please see our articles on safely lifting and supporting the vehicle as well as under body tray removal for additional assistance. Wear your safety glasses whenever you work under your vehicle.

You are going to want to replace one mount at a time while supporting and lifting the engine with a jack. NEVER remove both mounts at the same time while supporting the engine with only a floor jack!

From under the vehicle you can see both mounts (red arrows) and the access holes (yellow arrows) for the lower mounting bolts.
Figure 1

From under the vehicle you can see both mounts (red arrows) and the access holes (yellow arrows) for the lower mounting bolts. The right side mount has a heat shield on it to protect it from the exhaust (green arrow).

Support the engine from below with a floor jack.
Figure 2

Support the engine from below with a floor jack. Place a piece of wood across the oil pan to help spread the load and protect the pan (red arrow). NEVER remove both mounts at the same time while supporting the engine with only a floor jack!

You can also support and lift the engine by attaching a hoist to the front lift point on the motor (red arrow).
Figure 3

You can also support and lift the engine by attaching a hoist to the front lift point on the motor (red arrow). You do NOT need to do both.

Left Side- Insert a 17mm socket through the access hole in the lower cross member (red arrow) and remove the mounting bolt.
Figure 4

Left Side- Insert a 17mm socket through the access hole in the lower cross member (red arrow) and remove the mounting bolt.

Left Side- Use a 17mm wrench and remove the upper mounting bolt (red arrow).
Figure 5

Left Side- Use a 17mm wrench and remove the upper mounting bolt (red arrow). Use the jack and gently lift the motor until you can remove the old mount and install the new one.

The mounts have a locating nipple that must be seated in the upper mount that attaches to the motor (red arrow).
Figure 6

The mounts have a locating nipple that must be seated in the upper mount that attaches to the motor (red arrow). Use blue lock tight and tighten the bolts before removal of the right mount. 

Right Side- With the new mount installed on the left side and the engine still supported with a jack or hoist, insert a 17mm socket through the access hole in the lower cross member and remove the bolt (red arrow).
Figure 7

Right Side- With the new mount installed on the left side and the engine still supported with a jack or hoist, insert a 17mm socket through the access hole in the lower cross member and remove the bolt (red arrow).

Right Side- The top 17mm bolt is much easier to remove if you first remove the air filter and box.
Figure 8

Right Side- The top 17mm bolt is much easier to remove if you first remove the air filter and box. Please see our article on air filter replacement for additional assistance. With the box removed you can easily access the mount from above (red arrow). Remove the top bolt, lift the engine enough to remove the old mount and install the new one.

Right Side- There is a small 10mm bolt that helps hold the heat shield to the mount attached to the engine block (red arrow).
Figure 9

Right Side- There is a small 10mm bolt that helps hold the heat shield to the mount attached to the engine block (red arrow). If you need to remove this you can get access to it from underneath the headers. Note: the headers have been removed for photographic purposes only. You can also see the locating nipple on the mount (yellow arrow).


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Comments and Suggestions:
AnswerGrape Comments: Re: Dieselbenz1's comment re: figure 6 & corresponding description -

just a half-edumacated guess here, but I fear that others may interpret the text to follow for fig 7 as I did but fail to register the potential problem implied by "the engine still supported" statement. Not every noob out there will readily insert the missing detail that:

in order to complete the installation of the first left side one MUST lower the engine down onto the new mount in order to tighten the bolts correctly - n'est-ce pas?

THEN the bolts can be removed from the right side and the motor again jacked up.

...just sayin... as they say....
December 1, 2016
TonyC124 Comments: Now that it's stopped raining in Europe every weekend I finally got round to replacing the engine mounts on my C124 today. Following that experience, it's worth adding a note at the beginning of your tutorial to mention loosening the fan cowl, otherwise raising the engine to fit the new mounts is a problem. Also perhsps note to fit but not fully tighten all 4 mount bolts until you have both new mounts in place. That allows the engine to move easier as you fit the new and usually higher mounts in. BTW, the confusion about left/right may be due to the air filter position, which varies depending on age & model.
June 19, 2016
  Followup from the Pelican Staff: Thanks for the additional info and feedback. We appreciate it.
- Nick at Pelican Parts
 
melaw Comments: Are you sure the pictures fit the description? Right side instructions sound like left side and vice-versa...
November 17, 2015
  Followup from the Pelican Staff: left and right when sitting in vehicle. - Nick at Pelican Parts  
TonyC124 Comments: Thanks for the response Nick at Pelican Parts, and yes please, it would be really good if you were able to pull together one of your super step by step tutorials to guide through the process of changing the trans mounts. Like many others no doubt, I find that most workshops no longer show any real interest in cars of this age, and they charge a fortune for relatively simple jobs, but i still love my C124 and want to keep it maintained. It's also good to do it yourself and learn!
November 4, 2015
  Followup from the Pelican Staff: Thanks, we will get it on the list. - Nick at Pelican Parts  
TonyC124 Comments: Sorry, not that clear in my last comment - I mean of course the rear engine mounting, which I guess may be on the gearbox. I assume that there is some flexing in that, and perhaps some rubber parts, but it never gets mentioned in any articles that I have seen - why is that?
October 24, 2015
  Followup from the Pelican Staff: Most times we do cover the trans mounts. It may not have been authored yet. - Nick at Pelican Parts  
TonyC124 Comments: What about the rear mount?
Does that include rubber parts that may need replacing?
October 24, 2015
  Followup from the Pelican Staff: Yeah, I would replace the trans mount of you suspect it to be worn, or just plain old. - Nick at Pelican Parts  
Benz Mondi Comments: The reason for only on bolting and replacing one mount at a time is so that the engine can slightly twist rotate in place when it is raised up. In this way you are able to lift one side high enough to install the uncompressed new mount it is taller than the old one without the back of the engine hitting the firewall.
October 11, 2015
  Followup from the Pelican Staff: Thanks for the additional info. We appreciate it.
- Nick at Pelican Parts
 
Dieselbenz1 Comments: For figure 6 - Should add to use blue lock tight and tighten the bolts before removal of the right mount.
July 14, 2015
  Followup from the Pelican Staff: Thanks for the additional info. We appreciate it. I will have the article updated.
- Nick at Pelican Parts
 

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