bha

I have a 2007 S550 4Matic and have a bad vibration at idle.


Start the car cold.. the engine idles at the proper speed and is completely smooth. But the chassis of the car is vibrating. Feels like I'm in a tractor rather than an MB. Definitely something wrong.


Keeps doing it even when the car is warm. At traffic lights for example.


No change in Neutral or Park.


First guess was engine and transmission mounts. Replaced one engine mount (couldn't get the other one out so will have to try later) and the transmission mount.


Very very little change (almost none at all). New mounts are Corteco and are OEM so I'm sure they are the best ones I can buy.


*NOTE*: the ones I removed were also Corteco and if I'm reading the date code right, they're a year old. I just bought the car 2 months ago. Previous owner did say he replaced engine mounts but didn't say when. I guess he just did them recently!


Old mounts looked same as new. I've seen pics of collapsed mounts, even slightly worn mounts and they look different from the new ones. If I cleaned off my old ones, you couldn't tell the difference from new.


So obviously not mounts... but what's left????


I did hear from a very experienced MB tech that he runs into 4Matic bearing problems and he can rebuild the transfer case and put in a new bearing. He said it was reasonably common on this car and caused "vibration problems". He didn't say what kind of vibration.. at idle, moving, etc.


That conversation had nothing to do with my idle problem (he just mentioned it out of the blue as we were talking). But now I'm wondering if that bearing is bad and causing my problems.


I did read somewhere on a forum that "if you change engine mounts and the vibration doesn't go away, it can be the transfer case.. even at idle".


Has anyone had experience with a vibrating chassis caused by transfer case? Or anything other than mounts actually?


It seems that there are a limited number of things that can cause an idle vibration.. wheels, tires, and most of the 'moving' parts of the drivetrain are excluded easily because the car is not moving. So to me it has to be mounts or maybe 4matic.


Thoughts? Assistance? Would be appreciated!

androdev

Can be due to cylinder misfire. No error codes reported?

bha

Nope, it's definitely not an engine issue (misfire, etc.)


As soon as you lightly touch the gas pedal and increase the idle, the problem goes away. It's only a problem at idle speed.


Engine runs perfectly smoothly at all speeds and RPM except for idle.


With engine running and hood open, the engine does not vibrate at all. Usually with misfire you see some vibration of the engine and there isn't any.


Since the engine is fine and the motor/trans mounts are new, the only thing I think that remains is the transmission/transfer case. Something is turning and vibrating, and if it's not the engine that only leaves the transmission/transfer case assembly.


It makes no sense to me, as you'd assume the transfer case only has moving parts when the car is moving (I think of it kind of like a differential) but then my transfer case knowledge is lacking (they're a mystery to me) so I could certainly be wrong.

Quadcammer

the transmission and 4matic transfer case aren't moving at idle especially not in park.

what is moving is the harmonic dampner and the torque converter.

I would also consider removing the serpentine belt and see if that helps.

I have a similar issue.

corsaschnell

I have an issue with a cold start and vibration. MB Svc. Adviser tells me it is due to clogged fuel delivery system. He recommended using up to 3 bottles of Techron in the tank to clear things up. I am currently on the second tank with Techron additive.

I am not sure if this is the same issue for you but just passing on my experience.

Quadcammer

I call BS on that. My injectors after 55k miles and 10 years were nearly perfect.

the remainder of the fuel system shouldn't really get clogged. and techron wouldn't really help a clogged filter.

bha

To those who responded, thank you.


I guess I don't understand how these 4 could potentially be an issue:
Serpentine belt
Harmonic Dampener
Torque convertor
Fuel injectors


The issue is strictly at idle. Even when you press the throttle a little bit (raising idle 50rpm or 100rpm) the problem goes away.


The first 3 items (belt, dampener, and torque convertor) would be moving at much higher speeds when the engine speed is increased. So if anything is out of balance the problem should be the same or worse at higher RPM. Yet the problem completely disappears.


Same thing with injectors.. don't see how they can be a problem at 600 rpm (estimate.. don't recall where the car idles exactly) but yet at 700 to 4000rpm there isn't any vibration at all!


So yes I understand it should not be the transfer case (maybe the MB tech meant the bearings were noisy at speed rather than at idle). Although I did see a post somewhere a while ago saying that a failed transfer case bearing was proven to be the vibration source (at idle) in their W221. Seems weird to me but I will probably need to look into it.


I can't think of anything else that would cause a vibe at idle yet go away when idle is slightly raised.

Quadcammer

well, you have to look at it beyond rpm but also harmonics. The frequency of the crank vibrations differs based on rpm. It could be that a failing dampner simply can't dampen that particular frequency.

In addition, an issue with torque converter relating perhaps to incorrect fluid flow (broken vane or something) could be masked at higher rpm.

bha

Hmm.. interesting. That makes pretty good sense.


Is there any way for me to diagnose a harmonic balancer or torque convertor or does my indy tech need to do it? I do 90% of the work on my cars myself, but haven't ever tried to diagnose these parts before.


I'm sure they look fine (at least the harmonic balancer.. can't see the torque convertor) so how would I know a failed part from a good one?

Quadcammer

realistically, a STAR DAS computer would be really helpful in determining if you have an issue with the torque converter clutch, solenoids in the valvebody, or engine problem (gunked up throttle body, weak coil pack, etc). Harmonic dampner should really be diagnosable visually. If it wobbles or the rubber is coming out anywhere, thats a good sign of a problem. you can also use a little white paint to mark the metal pulley to the outer ring to see if the rubber is slipping.

Sounds to me like you have a torque converter or transmission issue. I know the valve body on the 722.9s has gotten a pretty bad rap. Could be related I spose.

RGS

I sure would consider the last unchanged engine mount before you do any more. Engine and transmission mounts are a notorious vibration problem. I had my OEM's changed at 40,000 miles with OEM's and it smoothed out an idle vibration problem. I would also want to know the quality/reliability of the replacement you used(Corteco).

That said, I have the same car(2007 4Matic) that has always had, in my opinion, excessive drive train noise during acceleration or deceleration-mostly at higher speeds(60+)----whining sometimes, light flapping sometimes. My previous car was a 2000 s430 2-wheel drive whose drive train was dead silent so it was noticeable immediately. I have attributed to the 4Matics extra drive train?

RGS

MBNUT1

My E350 4matic drivetrain was dead silent So much so I could pick up the faintest noise from the fan

39039

My 2012 s550 4matic have same issue. It is staying at dealership to check what reason with the idle vibration. This is 2nd time, at the 1st time, they replace the engine mount, but no improved.

bha

Agreed.. I will definitely change out the last engine mount but I don't have high hopes. The old mounts looked brand new and were a year old (per the date code). They were Corteco and so are the new ones. My guess is that it won't change a thing to replace that last mount, but I'm going to do it anyhow.


You mention drive train noise at higher speeds.. mine is completely smooth at anything except for idle. That's the weird part. No noise, vibration, or anything at 100RPM higher than idle speed (or higher).. even up to 100mph it is completely smooth.


This is a problem that effectively ONLY exists at a traffic light, when stopped with foot on a brake, or when parked with the engine running. No other time.

bha

Interesting. When they have your car done, would you mind letting me know what they did to fix it, and also what they tried on their journey to the solution (whether those things worked or not)


Would be interested to see what they try next after engine mounts as I'd like to do the same.

39039

Sure, I will update the result. But I also do not have high hope.

39039

I have picked my car for couple of day. The dealer felled that the vibration was normally, not obviously, they did nothing for the vibration. I wanna bring it another dealer to check next month.

castroadan

I have an 08 s550 4 matic and I am also experiencing this vibration. Car is in drive and my foot on the brake and it vibrates. I let go of the brake or put in park and it goes away.

Nickthegreek

You said you only replaced one mount. That could also be a problem. You have to replace both. I did both in mine and i dont have the problem anymore. Other possibilities maybe the throttle body could be dirty causing erratic idle. At idle it closes considerably so even the smallest difference can cause changes in air/fuel mixture whereas when you put your foot on the gas, it opens up and there is a lot more air rushing in
Or look for a vacuum leak

cmpcpro

I agree on the throttle body even the slightest bit can cause that to happen.

alx

Have the idle rpms checked and throttle relearned.

Nickthegreek

Can that be done without star diagnosis?

lganski

I am going to throw a few things out for you to think about. First the engine will vibrate the most at idle. The engine is mounted on rubber mounts to isolate these vibrations from the frame. I would throw the car on a lift to check and see if any part of the engine or its components are making contact with the body or frame including the exhaust. Let it idle on the lift and check for the noise.
I had a vibration on mine and thought I had a Cat problem but after putting it on a lift I found one of the forward exhaust clamps was rusted and broke free of its mount. Check these types of items before you get into the guts of the drive train. I have never run into a post in the W221/W220 forums that had a problem with a torque converter.

Nickthegreek

Wow! I tried doing what alx said on my car and it runs silky smoooooooth now!!! I have star diagnosis at home so i decided to fart around with it. Nice call alx!!!

Bill-W221

Nice !!!!!