[ArmyAnt]

I have a 2014 GLK350. Under acceleration, the interior of the car is so loud. Bought this car new, my wife drove this car for a few years and then we gave it to my daughters who drive it now. So, I dont remember the interior of the car being this loud when accelerating. If I had to compare to something, it sounds as if the catalytic converter is removed, but its not. I remember back in the day, guys would remove them from their trucks so that they sound louder, well...this is what it sort of sounds like. Its not loud when idling and its not loud when braking or cruising, its only under acceleration. Its pretty consistent. It seems louder when the engine is cold and not as loud but still very noticeable when the engine is warm.
Anyone else??

 

[Witek_M]

Engine mounts and transmission mount? X204 eats those for breakfast.

 

[ArmyAnt]

Engine mounts and transmission mount? X204 eats those for breakfast.

Thanks for the suggestion....I have very limited (actually zero) experience with bad mounts. So with that said, I dont feel any vibrations or hear any knocking that I would assume comes with bad mounts. But no harm in checking them today.

 

[Vailcoyote]

It sounds like an exhaust leak. Have you checked under the car to see if there is any damage or rust to the exhaust system?

 

[ArmyAnt]

It sounds like an exhaust leak. Have you checked under the car to see if there is any damage or rust to the exhaust system?

I checked briefly back when I wanted to make sure my catalytic converter was still there (it was) but I'll do a more thorough check while im under there.

 

[ArmyAnt]

Here's a view of the transmission mount from both sides. Not really sure what a bad mount would look like.

and here's a view of most of the exhaust system. I did not see any major rust, rust through or holes.

 

[John350]

If the converter(s) was missing there wouldn't be any question.

Block the exhaust pipes with a rag or something and see if the noise increases under the car (at idle, not while driving!)

Otherwise, you may have a loose baffle in the exhaust somewhere or the mounts may be allowing the drive train to contact the body somewhere.

Loose baffles don't seem to be as common as they once were, but they do sound a lot like an exhaust leak.

 

[ArmyAnt]

Also forgot to mention, the loudness seems to emanate from the front of the GLK. The sound fills the car (Im already kinda deaf) but it's very difficult to hear someone talking in a normal voice when under acceleration. And Im never in the back seat, but I definitely feel like the sound comes from the front. I might try to capture it on video. I'll post later.

 

[Vailcoyote]

I could be where the exhaust connects to the manifold. It's possible the gasket has failed.

 

[ArmyAnt]

I could be where the exhaust connects to the manifold. It's possible the gasket has failed.

I'll check. Thanks

 

[Brian Cole]

Mine has a bit of a throaty rumble from the rear at low speeds when accelerating. Like some muscle cars. Not annoying but noticeable

 

[ArmyAnt]

Mine has a bit of a throaty rumble from the rear at low speeds when accelerating. Like some muscle cars. Not annoying but noticeable

Yeah….”throaty rumble”. That’s a vey accurate description. Mines sounds like that but in the front. But it it fills the whole car. It happens only under acceleration. The sound levels off like diminishes as I ease up on the throttle like when coasting.

 

[markbenj]

I'll check. Thanks

Yes, it sounds like an inlet or exhaust manifold / gasket issue if the engine & transmission mounts etc are ok.

I have exactly the same symptoms on my W220 inline 6 cylinder S320 cdi (which should be almost silent apart from a distant high pitch diesel engine rattle). Much 'rasping / booming' noise from somewhere in or around the engine bay when starting from cold & accelerating - but a still noticeable low pitch 'thrumming / dis-harmonic' sound when warm.

Following with interest in case anyone else here has any suggestions...

 

[John350]

Mines sounds like that but in the front. But it it fills the whole car. It happens only under acceleration.

Are you sure there isn't something disconnected on the air intake side? I remember the roar when the two dumpers on a tri-power setup opened up...

 

[markbenj]

Are you sure there isn't something disconnected on the air intake side? I remember the roar when the two dumpers on a tri-power setup opened up...

Yes also. I've read on other forums that a loose / rattling air intake box & worn rubber mountings can cause metal-to-metal contact with the bodywork and create a similar noise / resonance. Worth investigating?