Hi Everyone,

Nice to be part of this forum. I have 2021 a new GLC 43 that I took delivery from just 1 year ago with, currently with 10,000 km. Everything has been fine (and fun) until recently we went to Costa Rica for 12 days from Dec 24, 2022 - Jan 6, 2023 and the Car was parked outdoors at the Park and Fly in Toronto. Weather was not very cold except for the first couple nights. I have all season tires on it (I work from home). So when we got back, it seemed like the parking brake was stuck. I pulled the release several times and the light stayed on. Anyhow I gave a bit of gas and it unlocked with a 'clunk'. Since then I have been getting a pulsating/vibration when the brakes are applied and it gets worse as I drive longer and the brakes heat up. I have already taken it to my closest MB dealer for the 1st Service A. I told them about this issue and to do an inspection of the wheels and brakes (which I saw afterwards on my invoice is included with the service A). Anyhow when, they said they did a road test and it was just ABS due to slippy roads and no winter tires (LOL). I told them I know the difference and then I found out they did not even remove the wheels nor inspect the brakes (Even though it says right on the invoice that I paid for that). So I got the service manager to drive with me and then he confirmed there was a problem with the brakes. He was also saying the problem is that I did not get winter tires and so the wheels can warp and also the problem could be attributed to the vehicle sitting for 12 days. This all seems bizarre to me. Has anyone else experienced this issue after their vehicle sat for a bit ? I mean I look at their lot and they over 100 new vehicles sitting there all winter, will they all have this problem ? Anyhow, I have another appointment this week specifically to address the brakes.
Shark_27 is offline

 

It's not unusual for brake pads to adhere to the disc, if they were wet when parked. Unfortunately, I don't know a way of parking without setting the parking brakes automatically.
That doesn't give the pad a time to dry out, and it can actually rust to the disc. It's not a flaw, but the friction will be different at that spot and you'll feel it every rotation.
You can see that spot on the disc by looking through the wheel and rotating it.

What is unusual is that it hasn't cleared up with driving. I would take it out and do a series of hard stops and see if that fixes the situation.
Odds are good that it will.
But again, I think it's unusual. I'd consider that series of hard stopping to be part of troubleshooting.
Give it a try and good luck.

 

I agree with mikapen. If I wash my car and then let it sit for a few days, the rear brake pads will stick to the disc and release with a clunk. Usually it clears up with a few hard brake attempts as mikapen stated. Tires flat spotting in the winter (especially low profile) after sitting a couple weeks is normal but should also clear up with driving. Techs obviously didn't check it out (surprise) and "Service Manager" is clueless. Go with your gut on this one, you sound like you know the deal.

 

Thanks for your replies. It has been 1 month today since it started and around 1000 km of driving. I notice the vibrating gets worse after I have been driving a while and the brakes heat up. Ive tried the hard braking several times and it doesn't seem to have helped much, if at all. It was really cold the day we left it in T.O near the Airport, December 24 as that storm was wrapping up, but it was pretty warm in T.O while we were gone. Seems to me that magnetic brakes rusting to the rotors would be a major design flaw. Wouldn't it happen to every car on the lot that sit there all winter ? I think there should be a way to release the brake if your car is going to sit for awhile, seems bizarre to me.

 

May need the rotors turned or replaced.
if one of the calipers needed lubricating on the slides
it could have heated the rotor and warped a little

 

As said above, your rear pads seized to the rotors due to rust and you now have deposits on the rotors. Sounds like they seized pretty good, partly I guess because they had 12 days to rust away. Every time those deposits pass under the brake pad now they cause vibration. The advise to do some hard braking to remove the deposits is a good one, the problem is the rear brakes don't do much of the braking, so it takes a lot of hard braking to have an effect. In the future you should not park the car outside for that long in the cold and wet with the parking brake engaged. It will automatically engage when you open the door, but just use the button to manually disengage it before the car shuts down fully. That way you don't have the pads in contact with the rotors for that long. If you can't get the deposits off with hard braking, you will have to replace the rotors and pads. Turning rotors these days is not advisable, because they have minimal material on them, so you'll be close to the minimum thickness after turning them.