Lots of threads about bad motor and transmission mounts. I want to recall reading somewhere that these problems occur on the older, pre-faeclift W212s, and that these mounts were redesigned for the 2014 and later cars. Am I correct in remembering this, or not?

Just compiling a list of things I want my dealer to inspect before the 2016 goes out of warranty...

 

Even on facelift models, the mounts should be checked. You'd also notice it from inside the cabin. They are not so much a "problem" as just a wear and tear item. I had my motor and tranny mounts changed around 40k miles.

 

Engine mounts are consumable parts, albeit 50,000KM class or 5 years usually.
It all depends on how you drive and how powerful your engine is, based on assumption all W212 non AMG share the same engine mounts.
It also depends on how bad your road is.
Their worn out state is over-deflection. Say when new it is allowed to move/deflect at 2cm, as it aged it moves more than 2cm.

Their rubber component also has duro level , the hardness, this will get brittle and or not very flexible anymore over time with use or no use, and also due to heat.
Imagine your tire, take a new at under 1 year old which has one 3,000KM and compare it to a 4 years old one same 3,000KM, the new one has more grip for sure.
For our engine mounts, its the vibration absorbing capability which gets worse and worse over time.
Even not using the car, the weight of the engine + transmission already applied a force to the mounts.

If you have owned many cars and from brand new, and you drive very aggressive, over time you will develop a better sensory feel of engine mount being worn but not yet offensively worn.
If engine vibrations due to bad mounts can be felt in the car cabin, that is already way too worn out.
One can catch it when it is still only minor vibration at the steering wheel at engine idle.
Its easier to sense the condition if the car is a manual transmission, play with the clutch and no brakes applied, one can tell engine mount condition.

Just keep it in mind, as DrDantheman1 explained, it is wear and tear item....but unfortunately no Maintenance Log Book will place a year or KM life on it

For myself, there is a time in my younger days where clutch and engine mounts last only 20,000 KM and under 2 years ( I was doing 15 - 20K a year ) on a front wheel drive car, small engine under 2 liters.
Front wheel drive cars engine + trans mounts work harder as it is the driving wheel up in front.

If you have a friend who has a say 25-35 knots boat using diesel inboard engine with long propeller shaft, it will have usually an adjustable engine mount.
Overtime due to age and pounding on waves all the time, the engine mount will sink-in and one need to adjust the mounts height/angle to match the propeller shaft flange.
There you can see engine mounts aging and its deflection visually in millimeters and new ones will be needed when there is no more play/adjustment room.
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My 18 y-old C320 with 120,000 miles (bought as new) has its original OEM engine mounts. No prob.

All the discussion about mounts on E-Class cars wearing out at 50,000km (31,000 miles) has me chuckling with skepticism, and yet asking the question...

 

Well , you must be a very calm driver and has good roads and lots of highway driving.
Now way I can achieve even 33% of that kind of mileage, not with my poor roads, my throttle habits and most importantly my sensitivity.
At your mileage in my city and me the driver, I would have replaced minimum twice if not 3 times , all front and rear shock absorbers + its top mounts, all ball joints or arm/link with such joints and tie rod ends too....aside from engine + tranny mounts.

Below. At 4years 3 months old, 11,000 KM , replaced on Aug 2018. Still very healthy mounts for 99.9% of owners, but no more "tight" feel for me. I don't like it.


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Locally here labor is cheap and parts like these are consumable, so they are quite cheap too ...fortunate for me.
Anything sold locally here as +10% above USA MSRP is considered fair price.
This mount in USA at US$124 ( MSRP supposedly US$162), locally cost me US$172 https://parts.mbfm.com/p/Mercedes-Be...122407017.html
What will kill me are products like transmission control module and similar slow moving high end electronics, it could be 200-300% USA MSRP.


I like my car to feel "tight" like new for as long as I own them , with replacing as often as needed any components which contribute to these "tightness", engine + tranny mounts so happen to be one of them.
My highest expenses on my cars are not the suggested maintenance regime by the book, which I cut them short by half usually any way...but keeping its chassis feel new always is the challenge for my roads.
Engine and transmission is easy to keep like new or very healthy, but overall chassis feel is not.

Locally in my city we car enthusiast have this term called CRICKET ORCHESTRA, its a noise inside the car when going over bad roads or roads with minor imperfection.
As the car aged,renewed suspension system or renewed steering system is not good enough as there are many bushings in the car which some are not for sale individually or a nightmare to replace and they do get worn overtime.
We then overtime get Cricket like sound coming from even the dashboard too. This is what I want to avoid in the long run, for at least 10* years age of the car ( *my max ownership limit is 10 years ) by replacing
all easy to replace NVH control components as soon as it is no more tight, even though they are still working decent.

I think my cricket sound to you guys would be very mild creaking noise.

I have two versions of car ownership profile for my family.
Wife/Kids use : 7 seater type, buy a new one every 3 years and max 4 years. Usually by 3rd year it would loose the tight/new feel because this car would be approx 20,000 -25,000 KM per year use,
hence the max 4 years limit because a 100,00 KM car is also my max distance limit.

My own car, up to 10 years max and also 100,000 KM.
I still have my 2011 Fiesta 1.6L now as my personal small car, only 24,000 KM today at 8 years old and it is already loose the tight/new feel by 2016 or so but still no Cricket Orchestra till now
Replaced all engine mounts in early 2018 and front shock absorbers mid 2016 and complete steering* system ( *under warranty ) in 2014.
I have a street comfort coil over kit which I will install on the Fiesta, hopefully it will improve the new car feel to it.

As for my E400, I already have full sets of Bilstein B4 ( comfort ) front and rear shock absorber which I will replace next month.
Today it is at +-17,500KM and I can sense on bad roads the original Sachs are not as quiet and compliant as it was when at 10,000KM.
I actually bought the Bilstein B4 hoping for mild improvement on body roll at high speed while adding nor harshness of the more sporty Bilstein B6. I was torn between B4 or B6.

Well that is how sensitive I am as a reference to why I replace NVH control components so early
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On my heavier e550 with the 4matic, I had engine and tranny mounts replaced at around 45,000 miles, dealer quoted me $3600 to get it done, yikes