mike10872

2018 GLS 450 68k noise from front wheel changed the pads only since rotor visually looks good. Old pads looked good also. Only happens early morning first brake depress, after a few stop signs it not heard for the rest of the day. Any ideas?

John CC

If it persisted through a pad change I'd look at the caliper sliders, and generally make sure it isn't hanging up (not retracting correctly). Then, you can try some anti-squeal compound on the back of the pads, chamfer the leading edge of the pads, and lube the edges of the pads where they contact the caliper frame.

Were the pads worn abnormally compared to the other side?

mike10872

Thanks John, the old pads had maybe 85% life remaining with both inner and outer wearing same. I changed them because the car was bought from a non mercedes dealer and who knows what pads were in there but they made the same noise only cold first thing in the morning. As per your suggestion and after asking a local mechanic he said also to use the anti squel spray/compound on the back of the pads with 2-3 coats. Another mechanic said also that the brake pads are hanging up. I will update the thread after, thanks.

mike10872

noise is still there after carefully inspecting caliper, regreasing the pins & pads edges, lightly sanding the pads, disc quiet spray at the back of the pads, caliper pushes back smoothly with C-clamp no sign of sticking, even bleed the brake line (all 4 done about a month ago). I've done brake jobs on my other vehicles but never an issue, the other front wheels is quiet as ever, no changes to the noise not quieter or louder making me think that it could be wheel bearing since the car parks at a slight incline overnight after backing into the drive way at night is it possible? rotor looks good but will not rule out the possibility. It's so hard to trouble shoot since everything is super quiet all day after the first 2 initial stops.

I personally would leave it as is but my wife leaves early for work and it's embarrassing to have the car sounding like that. Any suggestions?

John CC

1) use this stuff: Spray cans are for people looking for a quick fix.
2) clean the disk aggressively with CRC BraKleen, Buff the working surface with 100 grit silicon sand paper.
3) Make sure the pads don't bind in the caliper frame.
4) Stop worrying about what other people think...

[Edit] My question before about pad wear was intended to compare the left side with the right side, not the inner and outer pads.

If all else fails, you can try swapping the pads left and right, to help narrow down the problem.

mike10872

Good news this morning, no more noise, I replaced the rotors and with new brake pads (warranty swap) but believe the noise was caused by the inner pad sticking because it was touching the electronic brake sensor plug which was probably bent while handling the caliper There is very little clearance between the plug and clip that goes onto the brake pad, I open the screw that hold the sensor plug and carefully adjusted it further from the pad clip. To be honest this is the first brake job for me on a Mercedes and didn’t know what was normal on these sensors, afraid of braking them, only one side wheel has them so could not compare on the other side. Hope this helps someone. Thanks for all the suggestions.