ddombrowski

Did a brake job on the GLK this weekend and while I did find one users procedure written down, I didn't find one that had photos so I wrote up this quick one to hopefully help someone out in the future.

First, I went with Akebono Euro Ceramic pads as I've used these on many other cars and been very satisfied with the results. For the rotors, it appears that these rotors have seen at least 2 sets of pads as they're pretty grooved and have a significant lip on them, so I went ahead and replaced them.

I went with Wearever rotors from advance auto parts. With the exception of one rotor (out of a pair), I've had good results with these on several cars. It was a tossup between going with the zimmermans (good quality) versus the Wearevers at a significant cost savings. We decided to go with the Wearevers as a test. Skipping to the end - the wearevers are straight with no runout and they perform quite well. With AAP coupon codes the pair of front rotors came to $65.

Start by cleaning the rotor with some brake parts cleaner. I skipped a lot of steps in the photos - you have to lift the car (I did from the center jack point) and then place it on stands. Remove the wheel. Remove the 15mm hex head bolts that secure the caliper to the caliper carrier. Disconnect the brake pad sensor wire and wiggle the caliper off of the pads. Hang it from the suspension with something like wire or bungie cord to keep the stress off of the brake line.



Now, remove the caliper carrier bolts. In this GLK, the caliper carrier bolts are Etorx. I don't know the size (its bigger than 16). Instead of Etorx, I used my splined bolt tool, size 14. Other owners have mentioned that a standard 14mm socket will work here. Your call, but I wouldn't want to strip these. I bought a kit of 'spline sockets' in metric size, 1/2" drive from harbor freight for $9 with a coupon. Also note that these bolts are probably in there pretty good. I used my impact gun, but I imagine doing this by hand you'd probably need a good breaker bar or decently long socket.

Attachment 447122

After that, spray some PB blaster around the hub bore and in all the wheel lug threads, and in the rotor set screw. Rotor set screw is a T30 torx. After removing the rotor set screw, you can remote the rotor. Its probably stuck on there pretty good.

To remove the rotor, some say to just wail on it with a hammer, but I don't like potentially ruining the old rotors. You never know when the new rotor is the wrong part # or doesn't quite fit the hub right or has a manufacturing defect you didn't realize until you opened the package. I setup a block of wood across the lower rotor face and hit that with a sledge - the rotor popped right off.

Attachment 447123

Wire wheel/Steel wool the rust off of the hub and apply a light layer of grease.

Attachment 447124
Attachment 447125

New rotor on, set screw in place. Put the caliper carrier bolts back in. Not sure what the torque is on these but being that the thread size seemed similar to the wheel lugs I torqued to 90ftlbs.


Now you're going to have to press the piston back into the caliper. On smaller cars I've dont this by mounting the caliper and pulling it towards me, which forces the pistons back in. On a caliper this big with two pistons thats going to be tough so I used the old brake pad and a c-clamp. Be sure to check the brake fluid reservoir. I removed a few oz of fluid before I pressed the pads back in and still ended up overflowing the reservoir and having to clean up brake fluid. I underestimated the amount of fluid that comes out. Alternatively, you can crack open the brake bleeder, but I'd recommend against that unless you're comfortable bleeding brakes.



New pads next to old pads.



Install the brake pad sensor into the pad and put the pads in place in the springs. I reused the springs even though the akebono pads came with new ones.



Reinstall the brake caliper bolts. I think technically you're not supposed to reuse these. I used around 60ftlbs of torque for these.

Attachment 447130

Put the wheel back on and torque it down. Good to go.

Koenig1

Excellent write up!
I've been using the Akebonos ceramics for 8 months now, great smooth stopping power. I have them running with the more expensive Zimmermans. The old rotors were horrendously grooved, not to mention the continuous black sh-t covering the wheels. Please post an update on the 'Wearevers' once you have some miles on... significantly cheaper rotor price....
From what I hear (& seen) the orig MB pads eat rotors. My pads were still at 40% when changed out. I just couldn't stand the constant BLACK wheels!

mjhawkins2346

How about using Copper anti-seize lubricant on the back of the rotors? Any reason not to? I've used it in the past with brake jobs and it sure makes rotors easy to remove. I think the copper helps with heat transfer too.

ddombrowski

I just use regular old axle grease (says valvoline synthetic on the jar). Copper grease should be fine but you don't want to assist in heat transfer. You want to keep the heat in the rotor and out of the hub.

ble2716

Great write up.

The correct etorx socket is E-18.

As mentioned before, don't use regular (14mm) socket even it fits.

NYCGLK

thanks for the write-up.

I read that OEM rotors are soft and sometimes last less than the OEM pads. My pads look great with 46k miles. I'm going to check rotor thickness during next tire rotation.

ddombrowski

My personal, speculative opinion? I think the whole 'soft rotors' is mostly just shops playing it safe because they don't want a customer to come back and complain later. It makes their work look poor.

As someone that is not a professional shop, but has done many brake jobs for money, I kind of see where they're coming from. On one hand, I can tell someone 'you don't need new rotors. Just turn them, or even leave them be and do a pad slap and call it a day'. They save a little money and they go on their way. Halfway through their pads (so 1.5 pad lifetimes total) the rotors get too thin, or too scored, and they start to vibrate or squeal. Now the guy needs rotors (and has to pay labor all over again, so even more expensive than the original brake job) halfway through a set of brakes.

So, we replace the rotors with half the pad left and then what? They need ANOTHER pad replacement when the second half of the pads are gone. You've hit them for labor and had them in the shop 3 times instead of two.

Or....you tell them they need new pads AND rotors. Put a fresh set of everything on and the car has great brakes. The customer has to spend a little more money up front but at least is satisfied with the quality of the work over time and will be happy to come back. Tell them a little story about how 'the new rotors are all like this' to make them feel better about how much they just spent. 'Its Mercedes and their new engineering.....ya know?'

My personal opinion is that if you're paying for labor, I'd probably do a new set of rotors with the pads. If you do it yourself, just do a pad slap (2 pads per rotor) and call it a day. If, down the road, your rotors warp or squeal or whatever, you can do the rotors then, but if not, you saved a good bit of cash. Up to you. Since changing the rotors is an easy job for me I tend to reuse rotors more often and it usually works out where I can get 2 or even 3 sets of pads before they warp too much.

NYCGLK

I hear you...I'm not in rush to replace rotors. My plan is to keep driving until pads are done and replace everything. Brake jobs are easy, so I'm planning to DIY.

Did you flush the brake fluid? Would be great if you do a quick DIY write-up on how to do that with a bleeder. From what I read it's very straightforward, but never done it.

bop11

Here in PA, you have to have the rotors checked once a year, one front and one rear. On the inspection sticker they indicate which front and rear wheel they checked. I was surprised that the front rotors were under size with about 1/4 of the pad left. First time I ever had a rotor go thin before a second pad change in 50 years of doing brakes on my cars.

ddombrowski

I flushed the fluid about a year ago on this particular car. Funny actually, I had bought the pads and the fluid at that time to do the brakes because the owner of the car had been told at the dealership that the brakes were 'metal on metal' and needed to be done immediately. When I took the wheel off they had almost half the pads left! Ridiculous. So, I flushed their brake fluid and told them to come back in a year and we would do the pads and rotors then.

As for flushing it, don't sweat it. I have the motive power bleeder, but if I didn't I would say just to buy the cap (screw type for european cars). It comes with a standard air compressor type fitting on the end. You can connect it to your air compressor and set the regulator for around 15 psi and get the same effect (actually, its a little easier this way). Also, I never filled the motive power bleeder with brake fluid. I only used it for pressure and would top off the reservior after each caliper.

Anyway, as for a procedure, its been awhile, but I *think* you can get to the bleed screws on the rear caliper without removing the wheel but don't quote me on that. Fronts you will have to lift the car and remove the wheels.

First, siphon the brake fluid out of the reservior completely and refill with clean fluid. Then, apply your pressure bleeder setup and set it for around 15psi. Like I said before I don't fill the thing with fluid, I just fill the reservoir to the max and use the air pressure.

Working first with the right rear, spray some PB blaster on the brake bleeder screw. Use either a flare nut wrench or a closed wrench on the bleeder screw - don't use the open end. These bleed screws are soft and strip very easily. If you live in snow and salt - even worse. Crack the bleed screw and close it again quickly. Now connect your brake fluid drain hose line and run it into an empty bottle. Water bottles with a hole punched through the cap work great for this.

Now, use your wrench to crack open the brake bleeder screw and examine the fluid as it comes out the drain line. Look for air bubbles, dirt, debris, and color. The right rear will take the longest to change color, indicating that clean fluid has reached the caliper. I would guestimate around 15-25 seconds of fluid flow before it runs clear. If this is your first time bleeding calipers, stop the flow at 10 seconds and check the reservoir, then again at 20, 30 etc until you get a good feel for how long you can bleed before you have to refill the reservoir. You may have to refill the reservoir halfway on the right rear caliper (all the others *should* be doable on a one fill/one bleed basis).

When the fluid runs clear (and it may be hard to know your first time), its done. Tighten up (don't over tighten) the bleed screw and disconnect your drain hose. I turn until fluid stops flowing then + 1/4 turn.

Refill the reservoir and do the left rear next. Then right front, then left front.

As you move closer to the brake master cylinder, the time it takes to flush the line will be shorter and shorter. Drivers side caliper will be around 5-10 seconds to get clear fluid out.

Normally, on euro cars, I use ATE super blue (gone now) / ATE type 200 gold. For the MB, for whatever reason, I researched the spec fluid and decided to use the stuff from the dealership. Don't remember why.

I don't do anything to cycle the fluid out of the ABS pump. My opinion is that people make a big deal out of this for nothing. If it makes you feel better, jump on the brakes the next time you've got a straight section of road in the snow or wet and get the ABS to cycle which will get the old fluid out of there and mixed with the new stuff. Really, thats all you need to do.

ddombrowski

Wow...I stand corrected - maybe they are building them softer / thinner from the factory.

Another theory I've heard is that ceramic pads (which are becoming far more common) wear the rotors harder than traditional pads, which could also be true.

Maybe they're actually doing a different heat treat on the rotors, reducing hardness in favor of quiet operation. Who knows? I'm not a mechanic, I'm an engineer by trade, and unless you know the material spec of the iron that goes to the factory casting these rotors its all speculation.

I'm not that old but I too remember the days of getting rotors turned once and even twice before having to replace them.

We don't have rotor inspections in Florida so its never been an issue for me.

Mr. JLT

I plan to use brembo cross drilled and slotted rotors with ebc green stuff pads and some stainless steel lines. And a brake fluid flush with new fluid.

NYCGLK

ddombrowski,
Thanks for the detailed write up on the brake flush, that's very similar to another one I read for Porsche, so I guess they are all the same except some fill the pump and some don't. I like your method better, and read it's cleaner.

Seems that you are a Porsche guys as well, I bought 993 last year....what a fun car.

Lastly, Bob's post above is what I was referring to in regards to softer rotors.

ddombrowski

I have more experience with BMWs than I do with the Porsches, which are new to me. The 944 I own is a race car - stripped interior, roll cage, etc. It was a Spec 944 car in a previous life. I also have a second stock 944 that actually drives decently well but the great state of Florida refuses to play ball with the title work so I can't drive it. Its sad. Never did get into the 'real' Porsches, too expensive for me.

And yes, brake fluid flush is pretty common across the board (except for some dealerships that just siphon out the master cyl reservior, refill, and call that a 'brake flush'). The euro cars with the screw on cap are the easiest to pressure bleed. If you don't have a screw on cap like the american or japanese cars you have to use this chain device that wraps around the master cylinder. Its a pain in the butt and I usually end up having someone pump the pedal at that point.

rmfnla

Good write-up, but I would have replaced the springs, especially since new ones came with the pads.

Heat can cause springs to lose temper, and brakes get hot...

ddombrowski

They did come with the pads, so I was lazy in replacing them, but I'd have to disagree that they'd lose any heat treat, if they had any heat treat to begin with.

Most lower level steel alloys don't change structure until around 700C. Pads on a typical car/truck might hit 1100F/600C at their hottest, with temperatures dropping as you get further back into the caliper. Remember brake fluid boils at around 400F/200C.

Still though, they do age and theres no reason not to change them other than its faster not to. I've yet to see one crack or start squealing but I wouldn't be surprised if one did.

mbussado

Copper grease doesn't transfer heat anymore than standard grease. The copper particulate is for anti seizing properties... you're out thinking it too much...

tbishop

@ddonvrowski... how are the Wearever rotors working for you? I have a C240 and I'm looking to replace my brakes this weekend as the OEMs have warped, and the wearevers allaround pads and rotors are half the price.
I'm looking to get wearever rotors and their Platinum Pads for front and back. would you suggest them or the extra $100 for Beck/Arnley?

ddombrowski

They're fine so far, but its not my car so I don't drive it on a daily basis, or ever really. Every once in awhile I will ask the owner how the brakes are and I usually get 'fine' as a response. I don't think they care, which is good, because it means they're not warped.

I used wearever rotors on my wifes Honda Pilot. One was badly warped out of the box, which made me hesitant to use them on the Merc. I took the badly warped rotor back to AAP and they exchanged it and seemed unconcerned. The new one was straight and the car had great, smooth brakes after that.

About 50k miles after that, the Pilot's pads are getting pretty low and it has developed a noticeable warp. I will probably have the wearevers turned on the pilot and reuse them. I used them with the factory Honda pads that were on the car when we bought it.

Of note, the Pilot I believe had its rotors turned when we bought the car with 29k miles on it. They were already warped by 60k miles when I put on the wearevers. Now they're warped again at 110. Pilot seems to have a habit of warping rotors. Hmm.

Sorry, I realize I didn't answer your question. I would go for the wearevers over BA for the cost savings. When you buy them, be sure to use the AAP coupon codes (online ordering) and do in-store pickup. Using coupon codes I was able to get the two MB rotors at $65 FOR THE PAIR. As a side note, the wearever box actually has several brand names stickered near the UPC code. I think I saw BA, raybestos, and a few others. Should have taken a picture of it. I would not be surprised to find out all of the 'cheap' rotors are made in the same factory and re-branded, but thats just speculation on my part.

tbishop

Thanks. seems like if they aren't warping on your customer they should hold up fine. my main worry was not having comparable life (relative to price difference) and stopping power. But my MB ones are soft and warped so I guess that doens't really matter.
Normally I would cough up the cash untill this weekend I had to replace the Crank shaft position senson 18 mons after MB did it.... MB parts are supposed to be better than aftermarket .

Thanks for the information... This is this weekend's project.

ddombrowski

In my experience, the Akebono ceramic pads (and similar aftermarket ceramics) have adequate stopping power, but they do not have the same 'cold bite' that factory pads have. This means you have to get on the pedal slightly harder, but this is due to the pad choice, not the rotor choice. It also seems that ceramics are a little harder on the rotors than traditional pads.

With my previous car, a BMW E46, I regularly swapped out my pads when going to track days. I used akebono on the street and Porterfield track brakes on the track. Just after swapping, I would notice a huge difference in cold bite between the two, but after a day or two I just got used to it and forgot about it.

tbishop

okay. I mean unfortunaly I use the car as a station car 90% of the time and there are no tracks around me. with the amount of play they have now i'm sure I'll think anything is amazing once they are on. Thanks for the help. made my searching alot easier. there are so many brands and levels was spinning my head.

jgoga

Great write up, any issues with the rotors like warping yet?

John

miked807

DD*... thanks for GREAT WRITE_UP! .... great tips and suggestions.

for me - I have always bought "good/quality" rotors; and used softer PADS (usually the cheapest) > as my 'theory' was/is .....pads are most easy to replace & often DIY!!!

Rotors usually warp for lots of reason , some caused by driving habits , some are just how the "assembly" from factory works (since most cars these days are built to a PLUS or MINUS range of tolerance's/RANDOM PAIRS are always matched- Thus you will ALWAYS GET A WARPPED ROTOR!!!) IMHO - the only way you can fix the TWO MATE(ing) parts are by MANUALLY CHECKING the matching CALIPERS/ROTORS for each wheel(s) ....eg like most prof. racing teams do!

Thanks again for great write up!

NYCGLK

You know that when you replace pads on most cars right? The rotor replacement is extra 1% of the work (i.e. just slide the rotor off and put new one on).

The best would be to have pads that last as long as the rotors.