Mud

Whilst minding my own business on an exit ramp, I was surprised to hear grinding as my car came to a stop I check the pads frequently and even though I had planned to do brakes in a couple of months, they still showed some thickness left. My car has 48k miles on the original brakes/rotors. It has the sport package with the 322mm drilled rotors on the front and single piston floating calipers, all in all an average brake setup.



Anyway, that grinding seemed to come from the drivers side front, so I pulled the caliper and found ZERO material on the inner pad. All other pads had about 3/16".



The wear sensors are on the passenger side and those pads were fairly evenly worn.



The front rotors had been doing the cheese grater action on the pads, note the plugged holes on the inboard side on both rotors.






Typically, uneven pad wear can be a number of issues - stuck/corroded caliper piston, stuck guide pins, brake hose internal breakdown, or master cylinder. I decided to cover the first 3 things on the premise that the master cylinder was ok.

Parts gathering commenced. I don't care for drilled rotors on a daily drivers so I ordered a front/rear blank rotor and ceramic pad eline kit from R1 Concepts. I've used their stuff before and no issues after many miles. I think these look like Centric rotors which I have also used before. I'm not an aggressive driver, I just go with the flow. This isn't AMG/Brembo level stuff so some here may be disappointed but I'm fine with these selections.




Rotors had a decent cross-hatch finish. They also had all of the correct cooling vanes in the castings.



Pads. Note the part numbers that have come up before in threads here that reference Akebono and Duralast Gold. I don't know who makes these pads.



I also ordered front caliper rebuild kits, brake hoses and the rubber sleeves for the caliper pins. Incidentally, Rockauto sells the Pentosin Super Dot 4 for something like $8/liter. I ordered 2 liters and now have enough of it for my lifetime.



Masking paper applied so I could paint the rotors with black caliper paint. The picture above is with the painted rotors. I also painted the vane centers as well as the front/back of the hats. No paint where the e-brake shoes contact the rear rotor.





I had a concern about the front caliper pistons but they were perfect. So a bad or sticking piston seemed to not be the issue. Used the rebuild kits and all was good.






I did find that the caliper pins were dry, so I'm thinking that may have been the cause of the uneven wear. As mentioned, I also replaced the front brake hoses so I can't say for sure it was only pin or hose. Easy enough. A little trick to keep from losing fluid is to use a soft rubber cap with a couple of zip ties on the end of the hard line while you're doing your other repairs until you re-attach the flex brake hose.



Fronts done. VHT silver caliper paint was used. I will re-install the MB tags as soon as I get the vinyl stickers for them. I think its a nice touch.



Rears were generally ok other than some persuasion needed to get the rear rotors off. E-brake was not the issue, just rust at the center and behind the face. ALWAYS ensure that the hub face/edge and the back of the rotor hat (if re-using old rotors) are clean and smooth. You want them to fit together level and with full contact. I use a wire brush and a Scotchbrite drill pad to get those surfaces nice and shiny. I also put a light paint coat on the hub and then a very light smear of anti-seize that should keep the rotor from sticking. Future generations will thank me.

Here's what the e-brake assembly looks like.



Ready for rear rotor installation.



And done. New wear sensors came with the R1 kit as well.



Last step was to flush and bleed the system and then some controlled stops to start bedding the pads. Generally I have found the ceramics to get better after about a week of driving. All works fine, there is the new-brake improvement feeling of course but it was surprising to see the condition of the front brakes. But nice to know that the whole system is now working as it should.

EDIT: I wanted to mention a few things about caliper slides and pins. My suggestion is when you do the brakes, go ahead and replace the rubber slide boots at each caliper - they are so inexpensive that it's worth having everything new. New pads will come with metal slides that clip into the caliper mounting brackets - these are what the pad ears rest upon and slide a bit back and forth as the caliper assembly itself moves. That's essentially the definition of "floating caliper". Always replace those slide clips, along with any pad retention clips.
Check the caliper slide pins and attachment bolts - if the pins are corroded, replace them, they are not expensive. Same for the bolts, but get the right (graded) bolts, don't get ungraded hardware bolts. I typically use a wipe of anti-seize on the threads of all attachment bolts for caliper brackets and caliper attachment bolts, but others use Loctite Blue with equal success.
Be very careful about what you use to lube the caliper pins - the wrong grease can swell the boots and cause the pins to stick. I use Permatex Ceramic Extreme Brake Lube for pad contact points and the metal bracket slides (clips). I used to use CRC (the orange stuff) but it sets up a bit rubbery. That's ok for the pad contact points but on the slides, I wanted something that would set up but allow sliding movement, so I've switched to the Permatex lube. Syl-Glyde is used on the caliper pins, and only a light coat is needed, as the pins are protected by the rubber boots.

Here's a good example, actually on an E350, rear caliper pins and boots. That black stuff you see on the concrete and on the pins used to be some sort of grease at one time. Now it's a sticky goo that has reacted with the rubber boot and turned into a sticky gel material. There was zero movement of the pins inside the boots; in fact, one boot had torn from the caliper trying to move along the pin. I had to use pliers very carefully to work the pin loose, it was virtually glued to the boot and needed a lot of persuasion to be removed. The calipers were essentially stuck in place. When the brake was re-assembled with cleaned pins and new boots, Permatex ceramic lube was used on pad contact points, slides, and at the piston face. Syl-Glyde was used to lube the pins inside of the new boots. The repaired caliper worked like a dream, noticeable even from the brake pedal.



Torque everything as well, there's a reason why torque specs are given, and brakes are kind of important. You don't want brackets or calipers loosening.

thefisch

wow, great writeup with pics.

Mud

Thanks. I was actually a bit disappointed to see this fairly mundane brake setup in what I considered to be a premium sedan. I know it gets the job done but I'm thinking next go-round to consider at least a dual piston setup. I can see why many look into upgrades.

AirCooledTiger

Nice work and nice write-up.

I think your setup is fine. I think a lot of brake upgrades emphasize 'bling' and not functionality. Big red calipers and cross-drilled rotors look cool but pad choice, heat dissipation and stickier tires are factors to consider first if you want to improve stopping distance. Most of us aren't tracking these cars.

Mud

I agree which is why I went with blanks rather than drilled. And yes the brakes work fine, my comment was related to the initial price point of the car - at that cost seems that a bit of an upgraded braking setup would have been appropriate. But it is what it is I suppose. Thanks.
One additional comment I wanted to add is if you are rebuilding the caliper be very sure that the dust seal is completely secured into the groove in the bore. It can sneak out a bit while you are getting the piston all the way in. Check every mm of it with a flashlight. One of the seals did this twice and would have been missed on a casual inspection.

Here's an excellent video on brake basics. IMO Eric is one of the best mechanics out there.
https://m.youtube.com/watch?v=Yhw_d_EWrOQ

Mud

I thought I would add a bit of a postscript to this work. I did start to get an issue with one of the front rotors, brake vibration. I checked the runout and found that the runout was out of spec. I think as the brakes bedded in this became more apparent. Not terrible but noticeable. I also found an oxidized spot (blister) that you can see on the rotor surface just to the right of the dial guage. I almost always mic the thickness and check runout on new rotors (especially more inexpensive castings) and of course this time I didn't do that




Anyway, I contacted R1 and can't say enough good about their service. I sent info and pics, within one day there were 2 new front rotors on the way. Professional and courteous, A+ for me. I will buy from them anytime.

New rotors and runout were checked, all good, braking is well, like new brakes lol.

I also got MB vinyl stickers for the brake plates. I'm not 100% happy with the size but I did find alternate source that will make them almost to the same size and font. MB uses a proprietary font but Times New Roman is almost a dead match. Cost for the custom versions is about $20, so in the meantime I went ahead and used the ones I had. I figured the only ones that will call me out on them will be you guys As you can see the smallest I could find are larger than the OEM versions, but that's ok, I'll change them out a bit later, now have my honey-do maintenance list on wife's truck....

GuestFromTampa

Does E550 have a different brake setup than E350 ?
This is how my brake caliper looks like.

Mud

Looks like 550 has double piston calipers and maybe larger than 322mm diameter rotors. Makes sense since its a faster car with a bit more weight with the V8.

cetialpha5

Yeah, MB does something different on each model, I think E350 is single piston, E550 is double and I think E63 is triple but not sure. That's why the price for each one is different and they keep going up with hp.

aquinob

Appreciate the write-up with pix. I'm going to be doing brakes in the next week or so when all the parts come in. Just replacing pads and bleeding, unless I find something else wrong.

Mud

You bet. If yours is a 350, front caliper bolts are 13mm, rear are T7mm hex (allen wrench). Some time ago I bought a $25 eBay set of hex sockets of decent quality for this home mechanic. Made it way easier to loosen and tighten those types of fasteners rather than allen wrenching.
seller was autobodynow.
look up:

ABN Master Hex Bit Socket Set, Metric & SAE, S2 Steel and Cr-V sockets, 32-Piece

Also be really sure that hubs are clean clean if installing new rotors. Just a bit of grit or rust left can cause even new straight rotors to have run out. In my case it was issue with rotors themselves but just mentioning since sometimes the hub surface can be overlooked with the excitement of new shiny stuff lol.

diesel315

Great article and tips. Thank you