2010 E550 coupe; 33k miles. After completing the airbag recall, dealer tech checked the car and stated that motor mounts and transmission mount are "collapsed". Replacement cost about $1600. There is no vibration, no noticeable movement or noise under any conditions.....nothing. I then had my trusted independent shop check the car. They found nothing wrong. Am I missing something?

 

The signs of a motor mount collapse are very noticeable, and chances both the motor and transmission mount breaking at the same time are very slim, especially at that low of mileage. If there's no symptoms, and the Indy told you nothing is wrong, chances are you're good. Take whatever the dealer says with a giant grain of salt.

 

There's a reason they earned the name "stealership".
I think in this case it warrants a complaint because that's blatant fraud.
The front mounts will normally bleed out a good bit of oil when they fail, which you'd notice where you park. Plus they aren't both going to fail at the same time so in your case it means you missed two puddles of oil. The trans mount is/should be old school, meaning it's just a rubber mount like most all cars have and it's pretty easy to see/inspect it if you can get under the car. It's a little hard to explain how to tell good from bad since they good one has some movement and a bad one only has a little more movement. They're pretty cheap and super easy to swap out so I'd just replace it if in question. The motor mounts are much more $ and substantially more difficult to replace so if you're paying someone to do it I'd imagine it'll be $500 labor or more.

The trans and/or motor mounts apparently cause driveline vibrations because either will throw off the driveline angle. I can't imagine that little bit causing enough angle to be an issue, but people say it happens. Another thing is you may hear thumping going over speed bumps as the eng flops back down, or a mild bump if the trans is doing it. Another test, which is what I do for motor mounts; is pop the hood so you can see the eng from the seat, then hold the brake, put it in gear and give it a fair amt of gas. If the mount is wasted the engine will lift up quite a bit on the left side. It's normal to lift a little since good mounts have some give to them just like the trans mount, but if bad it'll come up like 2" and you'll know it aint rite. You can put it in reverse to check the right mount, but it seems in most cars it's the left that goes.
During normal driving you'll likely hear and feel the thump of it moving around so I can't imagine you would not notice, unless you drive like my grandma who says "drive like you have an egg between your foot and the gas pedal".

For a 2010 I'd say be wary of the mounts, but with only 33k maybe not so much? Maybe someone can chime in on the motor mounts, which I assume has rubber holding the oil in and rubber fails with time...

 

I had to do the engine and tranny mounts on my 2012 E350 A207 cab. at 56.5K. Driveline vibration was pretty bad at 35-45 mph. And the engine moved significantly under load. Mine were done by the stealer as part of the M276 engine rebuild due to the tensioner oil check valves failing and toasting the bottom end.

 

Hi Chevota. I appreciate your comments. I have a 2014 E550 with the twin turbo and I’m at 100k miles and I just started feeling random vibrations when I drive. I also notice it more when the engine is cold in the morning. Are you saying that even if your tranny mount has a little bit of rubber left it could still be bad? When I looked at at my motor mounts the rubber was not totally collapsed so it’s hard to tell if they are going or not. Definitely when the vibrations come it feels like they are coming from the engine. I feel the vibration in the floor and gas petal mostly. I feel it in 7th gear at low RPM when I accelerate. I don’t feel a lot of movement with I hold the brake and hit the gas.

 

Driveline vibration was pretty bad at 35-45 mph in top gear or 6th gear, matches what you feel

 

When I purchased my 2012 E350 C207 with 58k miles, it came with service records with the motor mounts being replaced at only 44k miles. ALTHOUGH, it was previously owned by a elderly woman. Not saying anything about sweet old ladies, but the "stealership" mentality may apply in this case. I could be totally wrong on that and they may not actually be of the best design, for longevity.

 

In the Stealership's defence, the mounts will have the appearance of "collapsing" well before they "fail"(leak). In this case, replacing them WOULD be a preventive maintenance call if the tech sees they are starting to fail and well within the realm of the dealerships job/position of maintaining your MB to it's Ideal state. Isn't that why you took it to them in the first place? I'm not saying that is what happened, I can't, especially without seeing the "failure" myself, but it certainly COULD be...

 

I was told I should replace my motor mounts in near future .I have no vibrations or noises in drive train. Doesn't mean they are not going to fail in near future. I know the motor mounts are filled with an oil or similiar liquid and its purpose is to cushion and isolate the motor /trans from the frame . I doubt if you would notice the fluid leak due to the under body panels .If the mounts sag or break there will be a vibration felt through the floor ,steering column,gas pedal ,through the seat of your pants ,as it would be grounding out on the frame.It has nothing to do with driveline angle ,the amount it would sag is negligible ,now a broken mount would let the motor rise on accel then slam down when off accel pedal with an obvious vibration .

I won't replace them until I have symptoms that indicate their failure.On my 911 the exhaust tips would be uneven and you could have driveline vibrations when shifting ,because the engine wouldn't be sitting in its normal position.After ten years on my E550 I'm sure they are a bit worn but not necessary to replace for awhile.

 

Motor mounts should be good till at least 50K but we have seen them failed at 30K+
They are almost a routine maint items. Almost all dealerships are default trained to suggest mounts on anything in their shop that isnt brand new.

 

it really depends on power output, honestly. My last set of motor mounts lasted just over 15k miles. I'll be replacing with ECE Billet mounts this time.

 

I was looking into this recently and the guy i emailed at ECE told me he wasn't sure if his e63 mounts would fit the 278 application. Have you figured out if they'll fit?

 

I emailed ECE a few weeks back and asked and they said "no problem, we have them in stock", but I have not ordered them yet. Probably going to be my Christmas present from the wife/kids this year. Mine is 4matic. I did read recently that they don't carry/make the RWD ones any more, but not sure if that is correct or not.