DaveW68

This symptom has been occurring for the last couple of months. When I start the car, it runs and idles fine. But when I hit the road, it runs very loud...almost like I have exhaust cut-outs and there is a vibration that I can feel throughout the car and what sounds like a wind buffeting noise. After the car is fully warmed up and at full operating temps, the car becomes quiet and the vibrations stop.

No check engine lights were coming on and I didn't pull any new or stored codes while all of this was going on. Last week, my check engine light finally came on, and I pulled codes P0505 and P20a2. I contacted the dealer and took it in for service. Apparently the codes were emissions related and a vacuum hose had become detached. They did not pull any codes for any misfires or anything else. After the hose was reattached, they cleared the codes and nothing new popped up. The problem is that the cold start symptoms are still there. The tech didn't see any leaks from the engine mounts, but said that at almost 10 years old, even though I only have 33k miles, those can go bad and cause vibrations. I asked why it would go away when the car is warm and he said that the exhaust gases can warm them up and the vibration can go away.

They've ordered the 3 engine mounts and will be replacing them, but I'm concerned that this will not fix the issue with the vibration and loud engine when cold. I figured that a coil pack might have gone bad, but the tech said that would throw a code if it was the case.

Has anybody else run into this issue? If so, what ended up being the problem and what was done to fix it?

1bad540

cant say Ive experienced this, I did notice mine ran better after an oil change? maybe switching to a colder weather oil would help?

DaveW68

Here's a short video. The colder it is outside, the louder and more apparent the vibrations until the car is warmed up.

DaveW68

Here's another one from last night. A little louder because it was a little colder outside. If you turn your volume all the way up, it will give a good idea of what it sounds like in my car before the engine warms up. Very loud with vibration throughout the cabin.

https://www.youtube.com/watch?v=YHco...ature=youtu.be

alx

Couple thoughts:

In order of likelihood imo:

1. You still have a vacuum leak somewhere
2. You have an exhaust leak or colapsed / torn exhaust bushing
3. Your secondary air injection pump has a sticky relay which keeps it on for longer and stops it when relay warms up and disengages
4. You have a colapsed engine/ tranny mount and drivetrain is hitting frame/ exhaust
5. You have blown header gasket or header bolts have become loose allowing exhaust gasses to escape until engine warms up and exhaust expands and closes gaps
6. You have a blown head gasket

Car is generally quiet so such a loud noise can easily be pinpointed with chassis ears. The dealer has the tool- tell them to use it if they are out of ideas

DaveW68

Thank you sir! I'll let you know if that are able to pinpoint the problem and report back.

Quick question: Would any of the items on your list throw a code or check engine light? Because I don't have any of those right now.

ruflife1

Had sort of the same symptoms and it turned out to be a pulsation dampener.

konigstiger

LI32.50-P-048280: https://mbworld.org/forums/s-class-w...ml#post3832463

T.H.Carrera

Sounds like an angry AMG.

DRTYLNDY

My initial gut feelings when I heard this sick V12 was it has an exhaust leak.
Johan

Mike5215

That blows. So loud though it shouldn't be hard to pin down.

DaveW68

It's only for the first 5 minutes or so until it's warm. Then it purrs like a ***** cat again. What may make it harder for tracking the issue is that it idles fine and while revving the engine in park it doesn't get loud. It only seems to be on the road where it roars and vibrates until fully warm.

Mike5215

It definitely is happening at a frequency that's decoupled from the drive train sound. (Love the way that V12 sounds BTW...never heard one before. That's the engine every 221 should have.) There has to be something making contact and rattling that's not supposed to be in contact. The key is the fact it goes away when the engine gets hot. Maybe that business about the mounts is correct. How's the warranty company been about handling the diagnostics?

DaveW68

Normally I can hardly hear the V12 as it is a very quiet car....much like a Lexus. And I certainly never hear the turbos whining or feel a turbo rush as the power is there immediately without any lag.

My warranty company pays for diagnostics if it leads to a covered repair. Motor mounts are covered under my warranty. I just wish it was something obvious that could be picked up through a thrown code. Their V12/AMG tech didn't pick it up during a test drive while the engine was still cold, which I find disconcerting, especially since the vibration and noise was very obvious when I left their parking lot after picking up my car. I really don't see how new motor mounts would get rid of the loud howling and buffeting sound. I think they're gonna have to get a different tech behind the wheel to pin it down.

Mike5215

Can they get the lead tech to go out on the drive with you? Shouldn't be a problem. Maybe run the car up there the previous night so it's cold when you take it out with the tech.

DaveW68

Good idea.

DaveW68

I got a call from the service adviser. My warranty company has authorized the replacement of all 3 motor mounts, which are now on order. My concern is that the tech didn't see any obvious leaks from the mounts (unless it leaked out a while ago and the sticky fluid has worn off)....and I have a feeling that it isn't going to take care of the roaring cold engine and vibrations. I guess these motor mounts will go at some point anyway, so it doesn't hurt that they are replacing them with the car being nearly 10 years old. But I'm hoping the my warranty company doesn't tell me that I'm SOL if it doesn't solve the problem and further work needs to be done to fix the problem. It sure would be nice if they could pinpoint the problem with STAR.

Mike5215

Were you able to replicate it with a tech in the car? Agree it seems unlikely that the only symptom of a blown mount is a rattle while the engine is cold. Sucks, both because as it stands it's ruining your enjoyment of the car, and also rendering it temporarily unsellable. Nobody is going to take on a TT V12 making that racket, so one way or another it has to get fixed.

Then again, these are strange and fickle beasts. Maybe fresh mounts will do it. If you think about it, the tranny mount might be the culprit. When it collapses, the tranny drops a bit and it can allow contact between the drivetrain and exhaust. When the exhaust is cold, the contact may be intermittent, causing the rattle. When the exhaust heats up, it expands enough to close the gap to the point where the contact is constant...no rattle.

DaveW68

I'm definitely not selling it. We are supposed to hit 58 on Fri, so we'll see if it is quieter at start-up with warmer weather. I have it scheduled for service on Monday where they are going to put in the motor mounts. They are going to keep it overnight and the tech is going to drive it Tues AM while cold and see if he can pinpoint the noise and will try to use the chassis ears to see if he can find the noise... if the motor mounts don't take care of the problem.

I suppose it could be the tranny mount since they did put in a new transmission last year. We'll see...

Wolfman

Couldn't listen to it as the video is listed as private, but we had to replace the motor mounts on our SL600 a few years ago.

Glad you got the repair covered. Mine was quoted over $3k for that. A bit more noise but mostly vibration.

https://mbworld.org/forums/sl-class-...-thoughts.html

DaveW68

Dealer told me it's around $1200 if it was a non-warranty repair for replacement of all 3 motor mounts....but under the warranty agreement, it's a little over $900. Not sure why yours were so expensive.

Wolfman

Sounds like there is more space in the S-Class engine bay. Our engine had to be pulled completely

DaveW68

Motor mounts were all replaced yesterday. The front left mount was broken and all fluid had leaked out. The right mount was collapsed and leaking, and the trans mount was wearing, likely from the vibrations. Amazingly, the car is smooth and quiet again. I'm not sure why the howling disappeared from when the engine was cold, but that's gone too. Total cost of the job was around $975, of which my warranty picked up all but my $100 deductible.

AMGSTIG

Hey Dave which warranty do you have again??? Not sure if I remember right but it's the one from your credit union?

DaveW68

https://mbworld.org/forums/s-class-w...who-s-bad.html