caf

I couldn't find any DIY info for the W166, but there was pretty good online info about the W164. The W164 uses 9 mm front caliper bolts, which is fairly standard; I think most of my BMWs are the same.

Alas, I soon discovered the front caliper bolts on the W166 are 11 mm. This is a rather odd size, and most hex sets do not include one. The conspiracy theorist might wonder whether the dealers have asked MB to cooperate in protecting one of their biggest and easiest moneymakers--the brake job! Anyway, I ordered one off of Amazon for $5, but anyone planning on replacing brake pads and or rotors should make sure they have the 11 mm hex bit available.

Otherwise the brakes are pretty standard, and shouldn't be any problem for the average do-it-yourselfer. I ordered front pads and sensor from pelicanparts.com for about $110. Shouldn't take more than about 30 minutes for each front wheel. There's only one front sensor to mess with, on the passenger side.

caf

I just changed the rear pads on my M350 Bluetec. The "Check Brake Pad" light had come on, and the rear pads were actually getting pretty thin. The inside pads were more worn than the outside ones.

The W166, like a lot of newer cars, has an electronic parking brake, EPB. Personally, I think these are an expensive, overly complicated alternative to the simpler systems on older cars. The EPB module failed on one of my Audis. Repair cost: $1200.

Anyway, before you can manually retract the rear brake piston to change the pads, one needs to disengage the EPB by putting it in service mode.

To do so, enter the workshop menu:

If you don't succeed at first, keep trying. It took me a few tries to get the workshop menu to come up. Mercedes actually made this pretty convenient; Audi requires an OBD reader tool to put the EPB in service mode.

Here's a little more info about the workshop menu where you can also check battery voltage and ad blue level:

https://mbworld.org/forums/new-m-cla...vice-menu.html

14MLBT

Got any pictures! Just curious... I like doing my own maintenance too!

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caf

Sorry, no pictures. But I'd be happy to answer any questions.

14MLBT

Did you have to take the brake line off to compress the calipers or it just slid in place? If you did what process or equipments did you use! I had an issue before on my 12 ML, piece if rock jammed between the pad and rotor. MB took care of it (warrant) but I still think they didn't because it was still digging in to the rotor.

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caf

You don't have to take the brake line off to compress the caliper piston. Once I remove the two caliper bolts so that the caliper is free, I usually use a crescent wrench handle between the old pads and twist slowly. The piston will slowly compress. As I noted above, on the rear brakes you'll have to disengage the electronic parking brake first.

Some people use a brake compression tool, but I've always used the wrench handle technique. Keep in mind that as you compress the piston, the fluid level will rise in the brake fluid reservoir. You may want to loosen the reservoir cap and put a rag around the opening in case the fluid backs up too much. If the reservoir has been topped off recently, you might even have to suck some of the fluid out first so it doesn't overflow.

Here's a pretty good illustrated DIY for the W164. You'll need the crazy sized 11 mm hex bit, however, instead of the 9 mm shown. I think otherwise it's pretty close:

http://audipages.com/Tech_Articles/s...350brakes.html

14MLBT

Thanks. Just making sure it's nothing special that differs from other vehicles. I'm a mechanic for 12 yrs now. I usually disconnect the brake line because the back pressure will damage the seals in the reservoir and for me it seems easier to put it back together. I learn something new every day, I might try your technique... Thanks.

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caf

Obviously your technique will work just fine, but then bleeding the lines is mandatory. My understanding is that there are no concerns about back pressure in modern systems. Just saw an online discussion about this somewhere else (but can't remember where!).

14MLBT

Sweet deal, I really don't trust anyone working on my vehicles. Knowing these technicians they hire aren't really up to the task! How do I know, I'm currently attending a technical college at night and just shake my head how clueless they are (some). To add to it, I've numbered my wheels from the inside and it wasn't rotated when it was supposed to. Thanks again.

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jwsbmwm3

caf, where did you get your rear pads? Do you know where to order rear rotors? What tools did you need (any odd hex sizes) The left side, rear wore right to metal. No lights or warnings came on. Appreciate response. This is a wife and kids car and she (wife) is making weird grinding and growling noises too.

caf

I ordered front and rear pads from pelicanparts.com. I don't believe they showed rotors on the site, but you could call them and ask if they can get them. I'm guessing that W166s are just now starting to need rotors. Other than the 11 mm hex bit I mentioned before, I can't think of anything unusual you need. Here's the 11 mm bit I used:



The sensor for the rear brake pads is on the right side, but I wouldn't expect wear to be much different for the right vs the left.

jwsbmwm3

Thanks. The right side rear has what looks like 20K miles (plenty of pad). That would explain no warning. I dont think MB USA is going to warranty this, though.

Mercapotamus

@caf - on pelicanparts.com they have Textar and Genuine MB rear pads, which ones did you get? I'd like to get the cheaper Textar pads but it only has a single review (maybe it was you?)!

Thanks.

Mercapotamus

@jwsbmwm3 - Did you have to get rotors? If so, what brand and where did you get them from? Appreciate any info you can share. Thanks.

And, Lmao @ the last sentence.

JRHolt

Thanks for the link! Just ordered the hex socket

caf

I got the Textar pads, but the review on Pelican is not mine. I've put a few thousand miles on mine and no problems or extraneous noise so far. I did not use the "goo".

Almost all German cars use something sticky on the outside of the pads to reduce squeal. BMW also uses a sticky liquid; some Audis and Porsches have an adhesive already on the outside of the OEM pads.

I've found there is usually enough residual stickiness from the previous installation that I don't typically have to add any more. Certainly not a bad idea, but if you do apply it, I'd use that stuff in moderation.

I didn't have any shudder or vibration before, and the rotor thickness was pretty good, so I stuck with my usual rule of only replacing the rotors ever other pad change. So no experience on rotors yet.

Mercapotamus

Thank You Caf. The info will definitely help out this noob.

Now to go to the local shop to loosen the lug nuts...

iankayem

Try this - CRC Disc Brake Quiet.

Mercapotamus

HELP! I followed the instructions as above and was able to disengage the EPB (made a rewinding kind of sound for a couple of seconds). After a couple of hours replacing pads & rotors on both sides of the rear axle, I tried to "Exit Fitting Position", and I got the "Cond. for Exiting Fitting Position not correct" message. And so the Parking Brakes don't work!


I most probably went wrong when trying to push/screw the piston back into the caliper. I was advised by the associate at Autozone to use the Disc Brake Caliper resetting tool on the rear calipers because of the "EPB spokes" in the single-piston that need to be rewound. So I definitely did that on the first caliper, but I got tired and lazy while working on the second caliper and I "pushed" the piston back (by retracting the backing-plate on the Tool by using a wrench on the Pressure Screw Assembly, rather than screwing the piston back by turning the T-handle. I don't know how to explain it better.)

I'll try to attach pics of the error message, the Piston and the Disc Brake Caliper resetting Tool.


Any sound advice is appreciated before I take the wheels off again & fiddle around with the Pistons.

Thank you.

Mercapotamus

Hah! This is just crazy! The problem seems to be fixed now, all BY ITSELF!!!

After 2 days of doing nothing to the car (because I was searching for a solution on the web, and waiting for a response on this forum - didn't find anything concrete and no responses), today I decided to have a go and fiddle with the rear caliper pistons. I thought, why not check the error message again. So I put the key to ACC position in the ignition, and what do you know --- a message "Exiting Fitting Position Reached To Confirm: OK".


So I'm hoping the piston and/or the parking brake cable(s) were only slightly out of alignment, and when I unlocked the car, the car did its pre-start routine and in doing so the piston and/or cables(s) aligned/tightened! Or something like that. I'm just putting it out there so that you know I DID think of the "How" it might've got fixed.


AND...the EPB does work; the brake pedal depresses when I press the parking brake lever to engage the EPB, and the brake pedal comes back up when I pull out the parking brake lever to disengage the EPB.


AND...I took the car for a drive to bed-in the pads. The brakes work and no squeals. But I'm definitely driving conservatively for the next couple a hundred miles!

OmniOtter

I just wanted to let you know how much I appreciated finding your comment about how to deal with the electric parking brake. I was searching around for probably 2 hours trying to figure out why I couldn't compress that dang piston. I created this account just to be able to say thank you - it really was a life saver for me.

Kevin350z

What's the torque specs to do the brake job? My ML350 petro only has 25k miles on it and I noticed the rear rotors are warped. Is that normal? I checked the pads they seem to be ok though.

joeban

Please I need the W166 Torque Specs to do the brake job?
I am in the processof changing the pads and I have the tendency of over tighten the screws. Torque specs will be greatly appreciated.
Do you have to perform the EPB procedure if you only doing the fronts pads?Rotor recommendation other then the Mercedes stock?

caf

Probably best to torque the caliper bolts to spec, but I wing it. They should be pretty tight. I always torque the wheel bolts to spec; I forget the number but should be in the regular owner's manual.

You don't have to worry about the EPB if you're only doing the fronts, the EPB only acts on the rear.

I used Textar pads from Pelican and they've been fine with no noise or issues. That's my only experience other than the stock. I'd be happy with either.

Dog hauler

I followed the procedure and all went well. Rear pads now replaced. The only issue is that the inside pad on each side was warn significantly more than the outside pad. The uneven wear was especially bad on the right side where the outside pad had much life left and the inside pad was almost down to the backing plate.

Anyway, I was able to exit the fitting position without issue. Is it necessary to do anything to correctly exit the Service Mode? Or do I just shut off the ignition and that does it?