Hi everyone, I am new to the forums and to Mercedes Benz.

I recently purchased an used 2005 E320 with 124k miles, which ran perfect when test driven. However, shortly after I brought her home, I began noticing a few things. One of which is a vibration from the engine.

I've done a few Google searches on the issue, which all led me a motor mount issue. However, my vibration differs from what is typically reported with a faulty motor mount.

It does not vibrate during idle.
Does not vibrate on the freeway.
Engine does not move more than a half inch when changing between P/R/N/D.
No signs of oil leakage from the mounts.
The vibration is linear to the engine speed, regardless of being in gear or not.
Almost temperature dependent, if I drive it for awhile, the vibration lessens.

Can this vibration be caused by anything else, other than a faulty motor mount?

Faulty transmission mount? harmonic balancer?

I posted this on benzworld.org, but only received two word answers: "motor mount", without any explanation. Is this a non-discussion topic and all type of vibrations is defaulted to motor mounts being at fault?

Thanks in advance MBWorld! I hope I can get more educated answers here.

 

Motor mounts are a common cause for vibration in the W211 which is probably why there wasn't much discussion over at benzworld.

Transmission mount vibration is quite rare on these models and it tends to be much worse under load. It is often accompanied by a knocking sound as the trans tail housing is moving up and down with loading and unloading.

A harmonic balancer failure would be more rare than a trans mount and that vibration is directly tied to engine rpm and will still vibrate at idle. It will also get much worse as rpm increases, then may disappear at certain rpm's as the harmonics begin to line up. Temperature wouldn't change a harmonic balancer vibration as it would be always be "out of balance" no matter the temp.

Motor mount vibration will often change with temp as the rubber and viscous fluid change with temperature.

A vibration is sort of hard to diagnose on a internet forum as there are subtle differences in how and where the vibration is generated. It's a tactile sensation where previous experience makes narrowing down the cause easier. Sometimes you feel it more with your hands on the firewall or engine. Sometimes it comes in by the seat of your pants, and sometimes you can feel it more from your feet on the floor board. Different feeling give different clues.

Wish I had more to offer, but motor mounts are a major cause for what you describe.

 

as Plutoe says, check your tires (unless you really KNOW this is from the engine and/or it happens when the vehicle is stationary).

1) I won't go into it further, but your accessory belt idler pulley may be the problem after the mileage you quote, though it's more likely to squeal than to vibrate without squealing. and I doubt it has the mass to cause all that much vibration)

2) Most of the symptoms you listed are at least consistent with the tires being out of round due to parking flat-spot deformations:

It does not vibrate during idle. (if you're not moving, your tires won't be either...)
Does not vibrate on the freeway. (the tires are probably warm before you get to the freeway and have rounded out the flat spots I am suggesting may exist)
Engine does not move more than a half inch when changing between P/R/N/D. (so, the mounts may be OK)
No signs of oil leakage from the mounts. (ditto)
The vibration is linear to the engine speed, regardless of being in gear or not. (Of course, the vehicle speed and hence tire rotation and vibration will vary with speed.)
Almost temperature dependent, if I drive it for awhile, the vibration lessens. (warm tires will round out and any flat spots from parking will reduce after a few minutes of tire-warming driving at speed. tire-related vibrations from parking flat spots are worse in winter, depending on the compound)

I have Continental Extremecontact DWS. They often get temporary flat spots while parked, especially in Winter. It's the compound. After a mile or two of warmth, they even out and stop vibrating. I actually recommend these tires despite this, if you live in an area that has 4 seasons.

 

This is great guys! I feel like this forum actually promote converations and investigation.

I have ruled out tires because the vibration can be felt even if the car is not moving and the engine is rev'd in park or neutral.