Hello all,

I have been following MBWorld for a good amount of time, silently reading people's experiences, especially while waiting in anticipation for my 2014 GLK250 BlueTEC, which I had ordered on August 31st. I took delivery on October 19th, and am extremely happy and impressed with the car. It is my first Mercedes-Benz, which is a long-awaited and happy moment for me. (My fiancée jokes that I was almost as happy when I picked up the car as I was on the day we became engaged. ) I would always go as a child with my father (a German immigrant married to an Argentine immigrant) to the dealers when he would buy his (he started with an '89 260E. Fun story, when I ordered my GLK, he decided to order a new ML350BT on the same day), so to finally have my own is quite something.

Anyway, on to a question for the mechanically and technically-minded. I ordered my car because there were no new GLKs with the driver assistance package. I am a firm believer in these technologies (I am a professor of computer engineering and computer science, so I should be!), and was pushing my dad for years to get a car with it. In the GLK, it works beautifully, I'm so happy I ordered it. So, because I can never leave anything untested, I built a simple radar-reflective rig to test out the PRE-SAFE Brake functionality. Watching YouTube videos such as simply wasn't cutting it. I had to try it myself.

After double-siding a foam posterboard with foil, I propped it up, made sure the car could detect it on radar, and tested it at around 6-7 MPH. Needless to say, it works! It works very well. In fact, it works quite exactly the way it shows in the video I just linked. After the beeping, the brake system groans, and you quickly come to a halt without so much as touching the test rig. (I didn't exceed 7MPH so as not to stress the system too much.) I tried it once more, just for the sake of repeatability, and the results were identical.

So, for those with intimate knowledge of the braking system, I'm guessing that activation of the PRE-SAFE Brake system might be a bit hard on the braking system. Even with hard braking from Distronic Plus, the brakes never make the groaning sound that you hear from the front when PRE-SAFE Brake engages. Is there a possibility that activation of PRE-SAFE Brake could cause any lasting effects? Knowing Mercedes-Benz, I'm sure it's all fine, that it works reversibly, and without any damage, but I thought I'd ask anyway. I've seen countless other demos of various MB classes executing PRE-SAFE Brake, and then continuing on and trying it again. I'm guessing that they wouldn't be doing that with the car if it would damage it. But, just having made such a large investment, I want to make sure that all is well.

Oh, and before I finish this post, I should comment on the AdBlue and MPG threads, in case anyone is curious: Roughly 2700 miles so far, thankfully yet, no CEL or AdBlue warning. My trip from Louisville to Dayton (where my parents live) and back is roughly 300 miles, during which I average about 41.5 MPG+ at 70MPH. Those of you who know that trip know that there are mountains that must be crossed, which can greatly affect fuel economy. When going on 55-60MPH stretches, I can get round-trip averages of 44 MPG+.

Thanks for indulging me in this long post, I always enjoy reading posts here, and hope to contribute at some point as well.
Regards,
-A

 

I'm wondering if the groaning sound is the ABS kicking in to make sure the tires don't slip?

I've taken the grill apart myself; the distronic radar sensor is located directly behind the large Mercedes emblem in the front grill. It's a pretty serious looking box.

 

While I'm sure that the ABS is ready to activate, I think that it's the brake unit going to full power, it's an impressive sound. I also thought it might be ABS activating simultaneously, but it's considerably louder. For sure, it's emergency braking, so they probably push everything to the maximum operating capability to make sure the vehicle can stop as quickly as possible.