Hello,

Pre-note: I have no idea what the correct vernacular is in regards to what I'm about to explain but I will do the best I can.

Essentially there are slew of problems that could be independent of all tied together. I've already taken it to Mercedes but they couldn't find out what or how to duplicate my problem.

Problems:

1. Brake buck = the car will engage the brakes as I step on the pedal then all of sudden the brakes disengage for about two seconds which allows either the tire or rotor to slip or skip and then engage. This happens wet or dry and almost always going down a slope at low speeds (10 mph tops). I call it brake buck because the pedal will try to bounce my foot off of it when this happens.

2. Tranny/Brakes= Whenever the car is started and the gearbox is switched to drive quickly (no gas has been applied yet) the car again seems to have a hard time letting go of the parking brake as it jerks a couple times and then begins to roll. Don't know if this is tied to problem one or not?

3. The battery died not to long ago just randomly. Turned out it was the original battery and was at least 6 yrs old (2011). Had it replaced but I've begun to notice the horn is beginning to become weaker and weaker. The new battery is maybe 2 months old. Start up sometimes takes a little longer as well. I mention this because maybe there is a underlying problem outside of the brake or tranny system that may be causing this.

Mercedes said there was nothing wrong physically with the brakes but who knows what else they looked into outside of the brakes. I mentioned abs because sometimes it feels as if abs is engaged randomly but they didn't say anything was wrong. The car has to have some sort of a problem At least in my opinion. (Whatever that's worth lol). The car is 2011 3.0L C300 Sport with 33k miles. If any one has experienced these types of problems I would love to hear from you. If you haven't I would still like your input. Thanks!

 

By chance, how worn are the tires? If they happen to be extremely worn or all but bald, could they actually be skidding, even at low speeds and the ABS is working properly?

Any lights showing up on the dash?

When you say it kind of jerks when you are trying to go from Park to Drive and release the e-brake it kind of sounds like you might not be giving it enough time to release. Give it another second before shifting to drive. Does that solve the issue?

 

Tires have less than 5000 miles on them so I don't think that's the case. No lights. No anything. E brake was/is never engaged and I've given the transmission plenty of time to be in the proper gear (about 15 seconds). However the car begins to roll for 1 second then begins jerking for 2 then everything is normal. I can give it more time but it's not like I start the car and switch to drive and try to take off in 10 seconds.

 

"2. Tranny/Brakes= Whenever the car is started and the gearbox is switched to drive quickly (no gas has been applied yet) the car again seems to have a hard time letting go of the parking brake as it jerks a couple times and then begins to roll. Don't know if this is tied to problem one or not?"

I am guessing it is just a confusion over terminology, but when I said '"e-brake" I was referring to what you mentioned as "parking brake". From what you describe you do use the parking brake. Maybe that is sticking slightly, but if that would be the case I am guessing that would throw a light.

Was your mechanic able to duplicate the condition you describe and still said there is no issue and that it is working normally? Or did they just say everything appears to be working?

How does it shift when driving? How are the motor mounts? Can you pinpoint exactly when this started happening, like right after having some service done, etc.?

 

Motor Mounts I am not sure. It first occurred a 2 weeks to a month after I bought the car in wet conditions. Didn't do it again until 1 month later in dry conditions. I thought it might be air in the brake lines. When driving it shifts normally but on some occasions it drives as if I have my foot on the brake when I don't. In other words it feels like something is holding the car back.