jpnn

Twice now I have shifted to reverse out of the garage after start up, and the gear did
not engage. Seemed to stay in neutral even with revving a bit. Same with Drive. Both times
it eventually popped into the gear with a higher rev, but with a scary clunk sound. Then worked fine. Has happened
twice out of a hundred start-ups. Anyone experienced this phenomenon? Thx

kblask

Definitely have not experienced the "clunk", but I have experienced the car feeling very hesitant to get moving upon shifting into reverse, mainly when drivetrain is cold. I've asked around, and seems the sluggishness is fairly common. The "clunk" sounds a little more concerning, however.

AMGRo

Long shot here, but did you wash the car and then park it? I thought there was something wrong the first time I washed it and then parked the car, because the brakes almost "rust" and the brakes semi bond to the rotors. And once you give it some revs they unbond with a pretty substantial clunk sound. Although, in my experience, I've never had an issue with the car not going into gear during this.

MalibuScott

Another long shot -- was the seat belt fastened?

jpnn

Seat belt not fastened, but then again it never is at that point. Car gets washed but this last
one did not follow a wash. The clunk feels like it is in the middle of the car and more like a it is
breaking out from something holding it in place.
I had it inspected at the dealer the first time and of course they could not replicate it and their diagnostics
found no issues. Very odd, especially since so infrequent.

Case1906

This really sounds like your brake caliper/pad seizing up against a rotor. It’s happened to me a couple of times on the next cold start after washing the car following a drive. It’s downright scary. The thump sound is literally the sound of the pad breaking loose from the rotor. To prevent this problem if you have it, drive the car around the block with some light braking after washing the car.

matteRAT

Mine did it right after I got it and washed it the first time. It sat in the garage about a week after wash before I went to drive it. It felt like it was not going into gear and would not move. I called 3 local dealers and no one had ever hear of this problem. I had a Mercedes Master Tech to try to help me via email and he thought the ebrake was not disengaging and advised me to disconnect/reconnect the battery to see if that would solve the problem. It did not. MB was getting ready to send a tow truck over and I read on the P forum about similar happenings. I went out and cranked it up and really gave it the gas. It made such a horrific noise (almost like a shotgun being fired) that my wife heard it inside our house. Looked at the rotors and you could tell where it seized. Now after wash I move it a few times to prevent happening again.

MBgt2018

I have had that happen on my GT and other cars.

Katie22

My 16 Maybach does the clunk if it sits for a week or so with no driving. It’s like the pads stick to a rusting rotor. My 18 GTC does not do the clunk but I have the ceramic brakes.

jpnn

Thanks! If this really is a brake issue, I will be very relieved. It is a scary noise that shakes the whole car.
The fact it has only happened in the garage leaving the house points to the brake theory too.

Katie22

If I recall there is a way to shut down car with parking brake disengaged. If you park car for extended periods try that and I bet you won’t have a clunk when you go to drive the car.

If I recall you shut down car with parking brAke switch pulled to release position to keep parking brake from setting. Give it a try.

BucsFan

After the first time I washed the car, it felt stuck until I rev-ed the engine and then THUNK. It kind of freaked me out. Turns out it was nothing more than the pads adhering to the rotors. Now I always pull the parking brake release I after I wash it. If that's all it is, then it's normal.

Surge

You’re supposed to drive around the block after a wash, to prevent the pads from sticking to the rotors.

I drive mine very little - once every week or sometimes every 2 weeks, and this has not happened. I would get the brakes looked it.

rt7085

After you wash it, when you park it in the garage or the like, pull on the parking release handle to release it (hold it and foot off the brake) and shut the engine off. The emergency brake will not engage and this won't happen.

612ride

I always disengage the e-brake before putting in to gear. It eliminates the normal hesitation, on these cars, of rolling. I have always had to do this on any of my Mercedes cars. Of course, that is not referring to the loud clunk noise some of you have experienced.