We purchased our new GLK 250 and for the most part have really enjoyed it, especially the fuel mileage. The car is pretty well equipped with the premium package , multimedia package, sport appearance package / 19" wheels also the keyless go and heated seats.

My concern is we had to take the vehicle in for a check engine light at 3500 miles. So while it was in I had them check the wind noise coming from the windshield at around 70 mph it's pretty annoying considering its a Mercedes ! In addition we have experienced on occasion a high pitched noise that sounds like a 18 wheeler is right next to you rolling down the highway.

So SD Mercedes did the warranty work and determined the check engine light was a bad NOx sensor, which was ordered and installed within a day.
The windshield wind noise has been reduced somewhat with the addition of sealer behind the windshield trim. They weren't able to eliminate the wind noise completely. I'm not real happy that this is apparently a design issue and is very noisy especially when you are driving in windy conditions
The loud, annoying intermitant noise wasn't duplicated after a couple of road tests / no fix, I hate gremlins. However the dealer stated it might be related to the run flat tires which are the Dunlop Grandtrek Touring.
Has anyone else experienced a nasty loud noise that lasts around 5 minutes while cruising the highway at 70. The engine remains responsive no loss of power.
I know what tire noise is and this really doesn't fall in that category, because I would be able to duplicate it on certain road surfaces multiple times. Please help before the engine or drive train grenades.

 

There have been some reliability issues with the 4matic on these, transfer case or something (been a few years since I read about it), I thought there was a thread on this forum. Didn't pay much attention as I have RWD.

 

I had read other complaints of wind noise when I got mine so I was critically tuned to seek the source. Did find what I felt was the real issue. I noticed the noise moved depending on speed and wind direction. I concluded it had to do with the turbulence caused by the roof rails. I can duplicate it depending on wind direction and speed. No problem. Normal. Likely the reason your shop couldn't duplicate and locate. I've forgotten about it. Mine is quiet enough!

 

This is just a guess. When the DPF (diesel particulate filter) was introduced, there is a burn off cycle that comes on at certain intervals. This is to burn off the diesel particulate caught in the filter. Not sure if this is true today. This could be the sound you are hearing.

 

any idea if this issue has been resolved yet? I read about the 2010 models being very prone to it.

 

Ive had zero issues with wind noise even up to 110mph. It's more noisy than a CLS550 that I've test driven, but it doesn't have such a vertical windshield either.

 

I had the wind noise issue and had the weatherstripping replaced. It helped a little but I'm planning on having the sealant added the next time I have it in for service. The loose rubber plus the steep angle of the glass contribute to the noise. It is there on every GLK, but some folks might not notice it if they are used to louder noise from a different car.

 

I wish the roof rails were optional like in Europe/South America. I was in Buenos Aires and saw a few GLKs with no roof rails. Looks much cleaner with a smooth roofline, probably has less wind noise, and honestly I don't think I'm ever going to use my roof rails.

Even though the GLK has a very respectable .35 coefficient of drag, it's not exactly aerodynamic, from the sides. Any cross wind is likely to cause noise with the brick-like side profile of the vehicle.