Strange New Engine Vibration After Changing Engine Mounts - Mercedes-Benz Forum
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post #1 of 37 (permalink) Old 03-24-2019, 04:29 PM Thread Starter
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Strange New Engine Vibration After Changing Engine Mounts

I changed my mounts and dampers yesterday. I even did my transmission mount, which is great because the one I removed came out in two pieces

I have noticed a much smoother idle, but I also have a strange and subtle vibration that only started after I did this job.

I can feel it through the accelerator pedal and through the seat, though it is slight. It only seems to appear under the following conditions:
-The car is in gear and accelerating from a dead stop (like leaving a ref light)
-The car is at operating temp (this doesnít seem to manifest when itís cold)
-Engine speeds are between 800-1100 RPM in park and then only at operating temp.

I speculated that since the old mounts were super collapsed, and that since the new mounts have my engine sitting maybe 3/4Ē higher for the first time in who knows how long, the throttle linkage adjustments might have been altered by the engineís vertical displacement.

Alternatively, I speculate that my raising the engine slightly to install the mounts and dampers (it came up maybe an incho and a half as a result of my lifting it with a transmission jack) could have upset something, but I have done several visual inspections with very bright lights and I see nothing out of place.
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post #2 of 37 (permalink) Old 03-24-2019, 04:43 PM
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Strange New Engine Vibration After Changing Engine Mounts

I didnít read this all but the transmission mount aka rear engine mount should also be changed. So with the geometry of the mounts, after reading it perhaps your drive shaft center bearing is worn from the previous condition. Your reply came in as I am typing adding edits, sorry in the car at a light


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Last edited by 281lxm; 03-24-2019 at 04:46 PM.
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post #3 of 37 (permalink) Old 03-24-2019, 04:45 PM Thread Starter
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I didnít read this all but the transmission mount aka rear engine mount should also be changed
It was also changed yesterday.
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post #4 of 37 (permalink) Old 03-24-2019, 09:13 PM
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I vote for the rubber bearing/bushing mount at the center of the driveshaft. I have a similar vibration when accelerating from a stop. OR up a steep hill at low speed. Does yours do that on a hill?

I got under the car and discovered that the driveshaft could be wiggled quite a bit in the center so I suspect the center mount.
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post #5 of 37 (permalink) Old 03-24-2019, 09:43 PM Thread Starter
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Originally Posted by 281lxm View Post
I didnít read this all but the transmission mount aka rear engine mount should also be changed. So with the geometry of the mounts, after reading it perhaps your drive shaft center bearing is worn from the previous condition. Your reply came in as I am typing adding edits, sorry in the car at a light
No worries, I appreciate the input!

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Originally Posted by luckymike View Post
I vote for the rubber bearing/bushing mount at the center of the driveshaft. I have a similar vibration when accelerating from a stop. OR up a steep hill at low speed. Does yours do that on a hill?

I got under the car and discovered that the driveshaft could be wiggled quite a bit in the center so I suspect the center mount.
The driveshaft seems solid on my car, and Iíve had the rear diff down before to replace the rear flex disc and all that. It didnít give me any reason to believe that the center bearing was worn.

Additionally, I get the aforementioned strange idle anomaly in park too, after the engine is warm and has been driven for a bit. So I hesitate to think itís driveshaft-related.
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post #6 of 37 (permalink) Old 03-24-2019, 10:12 PM
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Originally Posted by Wrench Jedi View Post
No worries, I appreciate the input!



The driveshaft seems solid on my car, and Iíve had the rear diff down before to replace the rear flex disc and all that. It didnít give me any reason to believe that the center bearing was worn.

Additionally, I get the aforementioned strange idle anomaly in park too, after the engine is warm and has been driven for a bit. So I hesitate to think itís driveshaft-related.
Just to clarify, I don't mean the bearing. I mean the rubber support around the bearing.
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post #7 of 37 (permalink) Old 03-24-2019, 10:47 PM
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What exactly was the brand of parts you put on the car now? Meyle, Lemforder, URO, etc? The rubber quality plays a role too, many times overlooked.
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post #8 of 37 (permalink) Old 03-25-2019, 07:04 AM
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Quote:
Originally Posted by Wrench Jedi View Post
It was also changed yesterday.


Just like I said in the pm to you
When I finished the thought while typing i n the car at a stop light.


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post #9 of 37 (permalink) Old 03-25-2019, 07:25 AM Thread Starter
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Originally Posted by luckymike View Post
Just to clarify, I don't mean the bearing. I mean the rubber support around the bearing.
Is that something that would cause my vibration when the vehicle is in park and idling?

I just drove the car to the gym, and it was normal and smooth up until it reached operating temp, then between engine speeds of 1000-1500 RPM, my vibration manifested. Usually when coming into throttle after exiting a corner or something like that. I am now sitting in the vehicle in a parking lot, in park, and I have the vibration again.

Iím guessing this doesnít happen often as a result of new engine mounts
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post #10 of 37 (permalink) Old 03-25-2019, 08:54 AM
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Originally Posted by Wrench Jedi View Post
Is that something that would cause my vibration when the vehicle is in park and idling?

I just drove the car to the gym, and it was normal and smooth up until it reached operating temp, then between engine speeds of 1000-1500 RPM, my vibration manifested. Usually when coming into throttle after exiting a corner or something like that. I am now sitting in the vehicle in a parking lot, in park, and I have the vibration again.

Iím guessing this doesnít happen often as a result of new engine mounts
Oops! I skipped right over the 'in park' part. No, clearly that takes the driveshaft out of the equation.

Well, you may have disturbed or changed something during the engine mount change. I'd probably spend some time carefully looking over the engine bay for anything out of place. If that didn't yield any answers, I guess I'd start with the troubleshooting tree in the manual, section 07.3-121.

I hate it when putting in new parts seems to create a problem.
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