Experienced home mechanic here with dozens of brake jobs over the decades. I have a 2014 E550, with about 52,000 miles on it. The front rotors and pads, though only a few thousand miles old from a dealer replacement, were doing a seemingly notorious warped / pulsy thing under any hard braking and I took it on myself, having done brakes on my CLS63, CLK55, and C63 without issue, just to hit RockAuto, order the Brembo drilled rotors and some less dusty pads. Parts arrived, everything came apart with no surprises and went back together, used a fast C Clamp to compress the pistons with the pad still on them so got them both at once. New pad slid right over the new rotor and into the grooves, back together - all good.

I DID NOT have to open the lines up or anything. Only did the fronts, didn't do anything to the rears.

After putting it back together, and firing it up, it stops-ish, but the pedal is soft on first press, and then rock solid on second - like you want that second press to be your first press. Soft in that way like you'd changed a caliper and have lines full of air, but that second press recovery is very odd.

I took it all back apart and examined the anti-rattle clamp things that attach to the front of the caliper, took the caliper back apart and as best I could figure, used them to apply tension to the pad. I'm reasoning that maybe the first press is compressing the caliper and putting the pads into order, and the second one is applying force? The anti-rattle thing is weird. It's like it WANTS to align in the journals where the pad travels, but obviously can't do that.

In speculating, maybe there was air trapped in the cylinders that I released somehow? Moreover, I'm thinking I have something wrong with these clips, it's the only thing that seems to be able to be screwed up here, and it's impossible to find anything about the A207 anywhere as any of you are well aware, let alone the E550 flavor.

Appreciate any help here. I'll start a right rear bleed and rotate around tomorrow, but I already did a front caliper bleed this evening and got nothing even resembling bubbles out. Fluid is also very clear - this is a summer only car that rarely sees any moisture or rain and stays in a dry garage.




The caliper in question.

The anti rattle clips / tension clamps

This is as best as I can figure they install, but they don't seem right.

If you try to move them lower, they're in the journals where the pads travel.

 

I have the exact same car, had the EXACT same issue. Drove myself nuts for MONTHS, bleeding the brake system at least 20x using every method known to man. Finally had the car at a trusted Indy tire shop, mentioned the issue and they fixed it. Guess what it was after all that…that exact clamp installed (by me) incorrectly.

I may have rushed through your post in excitement to help out, but I will take a picture of mine in the morning if you wish? I honestly haven’t touched the brake system since they fixed it

 

Would massively appreciate it. I knew it has to be this thing not holding the pads in the right place. Thanks in advance!

 

I figured it out.

My engineer brain was thinking there had to be some notch or groove or something they needed to hook onto. They literally just rest against the other part of the caliper and then the clip forms a spring to hold torque against the brakes. It just rests atop the other side of the unit - very simple. When I switched to using the original clips, it was very obvious, they had a much less pronounced notch on the end.

Brakes feel perfect. Never have felt this good on this car.





Top side of e550 w212 a07 caliper anti rattle clip

Bottom side of e550 w212 a07 caliper anti rattle clip

 

So glad to hear it, and sorry didn’t get out into the garage yet this morning. Congrats. I don’t know why that didn’t click for me for so long, kudos to you for the quick recovery!!