Missourian

My brakes were squealing loudly every time I stopped, so I brought it to the dealer and they replaced the front brake rotors and pads under warranty. They said the rotors had hot spots and the pads were discolored. The possibilities I can image causing this:

• Unlubricated brake hardware from the factory could cause the brakes to drag
• Air in the brake line from the factory could cause the brakes to drag
• The adaptive cruise control drags the brakes on the downhill of every highway rather than downshifting, and I use cruise control all the time. Here's a video of it dragging the brakes down an 8% grade in the Appalachians:
  You Tube

AKSwift

I don't know how often you go downhill with it, but I did ruin the brakes on our X166 coming from the mountains into Denver on I-70 last summer. Like you, I use adaptive cruise all the time and it hadn't crossed my mind that it would be braking non-stop for about 2 hours while trying to get a 2+-ton brick to stop accelerating past 70ish.

That said, by that point we had already had about 10k miles on the brakes, so 3000 sounds very low. No squealing here and I've been in the Blue Ridge Mountains for about 1000 miles over the last 8 weeks.

Glad they didn't argue with you over replacing them.​​​​​​​

nc211

That really doesn’t sound right at all, makes me think dragging caliper if just one, faulty system if all around. We’re 65k with plenty of meat left on the pads. Tons of stop/go usage too, and lots of cruise control in hilly areas. How’s your gas mileage reading? You’d have to basically have the brakes applied for the entire 3000 miles to wear them down that fast, regardless if using cruise control or not..

Given how insanely computer controlled everything is on these cars, perhaps a setting for the master cylinder is off?

SW20S

Sounds to me like the dealer didn’t say the brakes were worn, they were just able to substantiate a case to MBUSA to replace them because of your squealing. No way the brakes were worn down in 3,000 miles.

With that said, I come off of adaptive cruise when going down a steep grade so I can use engine braking. Like you said the car will just drag the brakes. Adaptive cruise isn’t appropriate for every scenario.

Missourian

The dealer didn’t say the pads were worn out, they said they were overheated. I never got a dashboard notification for the brakes, I just had loud screeching at every stop.

The paperwork said they replaced two bolts in the calipers. I don’t know if that’s their standard procedure for a brake job.

holeydonut

I just want to know what effing brake pads you all are using that don't spew nasty brake dust all over the front wheels.

mikapen

Metal from the discs is just as likely to cause dust as from the pads. Maybe more so. That's why modern wheel cleaners have iron removers.

Effing pads, if they're aggressive, might exacerbate the problem.

SW20S

On my S Class I'm just running ordinary ceramic pads that my mechanic sourced, brake dust is almost entirely eliminated with no reduction in stopping power

holeydonut

Any chance you know the brand of pad? And whether a part is available that fits a 2023 GLS 450?

SW20S

I don't unfortunately, he said that it was a small manufacturer he gets pads from and they don't sell directly to consumers. I know a lot of people on the S Class forum though use PowerStop Z23 pads and are very happy with them

stktyz33

I don't have a GLS but on my GLE, it will use brakes at low power (<10%) at times when coasting downhill with no Cruise Control activated. I think it's normal, it's a sophisticated system that appears to prefer using brakes and not the engine.

holeydonut

Hmmm ok I hope the 2022 MY GLS has the same brakes as the 2023 MY. They only seem to have Z16 and Z17 to fit the GLS though.

dfskinner

I think they told you what was wrong; in the report, they replaced two bolts, I think your brakes may not have had the bolts to start with, which caused the brakes to drag, wearing them down much quicker than normal. I changed my front brake pads at 120,420 miles on my 2019 GLS450. That's the first change of the front pads, I changed the rear pads about a year ago.