ToanPham

Happy New Year everyone.

I have a question to owners of M256 engine in S or any other Mercedes.

I have a w222 2018 with this engine (Japanese) with 17000km on it. I have noticed vibration on cold starts. The sequence is as follows.

1/ cold start
2/ smooth at 1200rpm
3/ SHUDDERING through cabin at 800-1000rpm
4/ smooth at 500-600rpm warm idle

happens regardless of aircon is on or off. Engine run smoothly and rev freely otherwise. Have done a B1 service last week and nothing has change.

Thank you heaps in advance.

W205C43PFL

Do you feel the vibration throughout the cabin? Like the steering wheel, the seats?

ToanPham

Yes, exactly. The whole car goes wobbly.

dlafever

Perhaps not engine related but due to AIRMATIC compressor running at cold start? You could confirm via increasing engine speed slightly while immediately following the cold start, if the noise does not change then I'm guessing it's the pump vibration dampeners.

I recently replaced the vibration dampeners on my W222 and all is quiet now. Previously it sounded like a compressor (go figure right?!) and I could really feel it in the steering wheel but the rest of the car as well. The pump is located in front of the left front wheel, facing forward.

There are three vibration dampeners that the pump sits on and after they age for a few years they lose their shock absorption. It's a pretty easy job to replace them; wheel off, fender liner off and there's the pump staring at you.

Check out this video, all the pieces shown. Also if you do decide to replace these cushions, please consider replacing the air pump filter as it is very cheap insurance against having the replace the pump due to dirty air.

ToanPham

Hello again.

Here’s a video of this morning start up. A lot of tap tap clicking sound coming from turbo side of engine. Does this sound normal.

the vibration starts at the first “downshift” of engine tone. cheers.

https://share.icloud.com/photos/080O...PByEF_W4Yr9ioQ

chassis

With the car almost 6 years old depending on build date, could engine mounts be on their way out? MB engine mounts are soft and known to fail earlier than most people think they should.

dlafever

Goodness it's been a while since I've worked on a Mercedes diesel! That chirping noise, no idea if it is normal or a belt or some vacuum valve or leak... The diesel part makes me think what @chassis mentioned, engine mounts, especially on a diesel.

ToanPham

To follow up. I’ve done mount testing in attached video.
what’s your opinion. Thanks heaps.

https://share.icloud.com/photos/0a8_...uR0KSadkkMxvig

dlafever

That's enough movement for me to replace the mounts. It could only be one bad mount at this point, it usually starts with one going bad, but the other is soon to follow.

ToanPham

Thanks heaps everyone for your input. Will post update.

W205C43PFL

That is indeed a lot of movement, replace them and everything should be good to go.

WRC-LVR

Huge amount of movement in drive...I'd replace the engine mounts and tranny mount as it goes bad too. OEM ones should last ~ 40K

WRC-LVR

Do both engine mounts...That way you have fresh mounts on either side of the engine and it wont be drooping on the collapsed side causing issues. I highly recommend both PLUS the tranny mount be done. Tranny mount is simple...

ToanPham

Hi everyone.

Just to update, took it into a large dealership and they didn’t want to change them, saying no issues with mounts. Didn’t have time to diagnose my vibration though as my engine was hot. Had to leave overnight which they didn’t have a loaner car for me.

I will book it in for full assessment next month.

Thanks again everyone.

WRC-LVR

Was that a Mercedes Benz Authorized dealership ? That is Dealer speak for we did not do anything at all. Engine hot would not prevent them from doing the mount inspection and engine running torque test. Find another dealer or just get them to replace anyways.