2007 w211 rough idle after mounts replaced - PeachParts Mercedes-Benz Forum

bkc · #1 04-30-2020, 03:12 AM

Hi all. I recently replaced the blown motor and tranny mounts on my 2007 w211 E320 CDI (labeled Bluetec but isn't). It actually had a pretty smooth idle prior to changing out the mounts, despite how bad they were. Afterwards, it is a much rougher idle (kind of hurts my head if I am leaning back on the headrest). Even my wife commented on it to me, so it isn't just me being oversensitive to things.

Items of possible note:

* No current or pending codes (Autel MaxiSys Elite scanner)

* MPG and performance seems normal

* When removing the cat to replace the right side motor mount, the DPF upstream temp sensor broke (was clearly on last legs once we looked at it). Replaced, tests fine.

* Mounts are Lemfoerder

Any thoughts on what to look at? Something I might have missed or done wrong?

Thanks!
-Bruce

Sugar Bear · #2 04-30-2020, 09:55 AM

The new mounts would have changed the position of the motor and trans. This may have caused something to contact the body transferring vibration directly without any cushion/insulation. Check the exhaust system, air conditioning lines and high pressure PS lines for contact.

Also check the new mounts for possible failure/collapse.

How was the motor lifted for mount replacement?

Good luck!!!

bkc · #3 05-04-2020, 09:43 PM

Haven't had a chance to get the car on a lift yet (which is a good thing, since that means we've been seeing an uptick in business)

We did check for apparent contact points the day after, when I drove it home and felt the vibration. Did not see anything, but we might have missed something.

Visually, the mounts appear to stand at the correct height. They have a white rubber cover over them, so hard to directly measure, especially the right side one which requires removal of the cat to replace. Will try to get it up in the air to measure and check the heights.

The motor was lifted one side at a time with a screwjack and a 2x4 across the oil pan, while the car was up on a 2-post lift.

One interesting thing I noticed checking on the parts invoice: WorldPac no longer lists those part numbers (220-240-33-17, 230-240-04-17) as selections for my car. The original invoice stated that those replaced the original order of 211-240-30-17. Visually, the new mounts looked correct, but perhaps they have some subtle difference? The anti-spin tabs lined up, and the shape and heights looked correct. But if I search on those part numbers in WorldPac, they don't list 211-240-30-17 as a related part. Might be nothing of importance, but still suspicious.

Thanks!
-Bruce

g300d · #4 05-05-2020, 04:06 AM

Maybe the arms? I've experienced broken engine mount arms in W123's and W124's.

bkc · #5 05-23-2020, 10:04 PM

Three of us looked it over and can't find anything rubbing, or otherwise potentially increasing the roughness. One guy thinks the mounts have different valving now, firmer. Will see if it "settles in" over the next few months, if not will warranty out the mounts and try again (especially since, as noted earlier, I am suspicious of the part numbers WorldPac provided, given how they aren't applicable anymore). Thanks for the suggestions, all. I'll try to report back if I eventually find an answer!