#mount

Doug writes:I have a 2007 Mercedes-Benz S550. I accidentally bought it in 2014 off eBay (long story) for about trade-in ($13,000), with 150,000 miles on the odomater. In a twist of good luck, it turned out to be a one owner car and using CarFax I was able to see and verify that it had been maintained by the selling dealer right up to a few weeks before its eBay appearance. A call to the dealer confirmed the complete service history. Even the brake pads and rotors were new, and it had a newish and very expensive set of Michelins. Almost three years later, it has been very reliable for my teen daughter and has 180,000 miles. It had a few quirks I have fixed myself (clogged charcoal canister, minor trunk leak caused by a missing rubber plug, sticking power driver seat) and only one real repair (dead stereo amp rebuilt by Becker).Now that my daughter is off at college and content with a ZipCar, I am driving it and intend to keep doing so. I have noticed a vibration in the center console area of all places, while driving around town. You feel it through your arm resting on the console lid. It’s a deep vibration, if that makes sense — coming from under the car.You don’t feel it in the seat, nor do you feel it in the steering wheel. You do not feel it at a standstill, just at 20-30 mph. It goes away at higher speeds, and the car is rock solid and smooth as glass at 75 mph. I am stumped as to the cause, and with the age of the car, I don’t want to set a dealership or even an indy shop loose on it without more of an idea of the cause. I was thinking maybe a motor mount, but it seems like I would feel that all the time, and especially at idle, which I don’t. I was wondering about maybe some kind of driveshaft or transmission mount or connection point, but it seems like a fault that would get worse with increasing speed instead of going away. Do you have any ideas?

We had two updates to a previous Piston Slap this weekend, surprisingly within two hours of each other. Let’s hear from the OP first:

TTAC Commentator sundvl76 writes:

Sajeev, reporting back:

You may be interested in this, if for no other reason than to add to your diagnostic toolbox; my experience certainly can’t be unique: Several comments below your post also suggested the motor mount(s) as the problem. I more recently discussed this with a professional wrench acquaintance, who also said that the mounts can be expected to go south after ~80K miles; he suggested using a padded floor jack to lift slightly on the engine during a time when I detected the “rough” idle (the oil pan on this vehicle, and maybe all Duratec engines, is waffled cast aluminum). Bingo! The vibration ceased when I did that.

TTAC Commentator sundvl76 writes:

Sajeev,

Your post of 2 Mar 2011 was a great explanation regarding the cause of the “T” joint oil leak I’ve been experiencing. No one on any of the normal Ford sites has been able to pinpoint the problem, so I thank you for the information. (I’d discovered the source, but didn’t know the cause/fix until your post.) TTAC is now on my Favorites list!