Can't get the rear brake piston to compress! 2016 CX-5

I scrolled through that video on the CX-9 brake job, and nowhere did I see him talk about going into or out of maintenance mode. That's scary stuff.
I've watched a few youtube videos now on Mazda rear brake jobs with EPB's, and no two guys do it the same way.
Most of them are amateurs and look like they're just winging it, pretending to be experts.
One guy didn't remove the EPB motor, while others did.
Some guys lube the pins, others didn't bother. It goes on.
My advice for anyone contemplating doing this (I'm one of them), is to watch as many different videos as you can, and take the best practices from each one before proceding.
 
$150 for brake pads? Where I live, it ranges from $210 to $500 depending on how greedy the dealer wants to be.... :(
 
As a follow-up... with some help, I've managed to solve the issue. I will try and post some photos tonight when I have it more apart.

Basically, I had to get some help and we had to further take everything apart. The EPB motor turns a collar that engages a screw and that can move the piston in and out. When the EPB was put in maintenance mode with no pads, the screw came all the way out of the collar and because of the way it can kind of float in the caliper it's pretty much impossible to get it back in and pushing the piston straight in will not get it in. Taking it all the way down is the easiest way to do this and in fact on the side where I didn't monkey around as much I was able to get everything back together with some help in not too much extra time. However, in the side where I really monkey'd around with stuff the collar and screw became crossthreaded and I'm lucky we were able to remove it.
 
dpvu said:
As a follow-up... with some help, I've managed to solve the issue. I will try and post some photos tonight when I have it more apart.

Basically, I had to get some help and we had to further take everything apart. The EPB motor turns a collar that engages a screw and that can move the piston in and out. When the EPB was put in maintenance mode with no pads, the screw came all the way out of the collar and because of the way it can kind of float in the caliper it's pretty much impossible to get it back in and pushing the piston straight in will not get it in. Taking it all the way down is the easiest way to do this and in fact on the side where I didn't monkey around as much I was able to get everything back together with some help in not too much extra time. However, in the side where I really monkey'd around with stuff the collar and screw became crossthreaded and I'm lucky we were able to remove it.
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Thanks for the update. Since all rear disk brake calipers on 2016 CX-5 with EPB have some manufacturing flaws based on the TSB which would cause EPB dragging or locking-up, I’d get a pair of newly revised rear disk brake calipers and just be done with it for safety reason.

TSB R052/16C: Noise from REAR BRAKE/Trace of Rear Brake Dragging
 
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So I couldn't get good photos but the diagram in the TSB is pretty good. The EPB motor (A) turns the screw (B) to retract or compress the the brakes just enough to apply the braking for parking. I believe the purpose of maintenance mode is actually not to protect the motor as much but to retract the ball and ramp (C) so the piston can be pushed straight in. In my case, the screw (B) got pushed out so far it was no longer in the collar and trying to push straight in and turn the screw would have worked but it's very hard to get lined up. On one side I ended up crossthreading it pretty badly.

Capture.PNG
 
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dpvu said:
So I couldn't get good photos but the diagram in the TSB is pretty good. The EPB motor (A) turns the screw (B) to retract or compress the the brakes just enough to apply the braking for parking. I believe the purpose of maintenance mode is actually not to protect the motor as much but to retract the ball and ramp (C) so the piston can be pushed straight in. In my case, the screw (B) got pushed out so far it was no longer in the collar and trying to push straight in and turn the screw would have worked but it's very hard to get lined up. On one side I ended up crossthreading it pretty badly.

View attachment 227081
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The TSB says:

DESCRIPTION
Some vehicles with the electric parking brake (EPB) may exhibit the rear brake dragging resulting in brake noise and the outer disc pad abnormally worn out. Or the vehicle may roll momentarily when starting from a standstill with the EPB applied. (The EPB is not automatically released for both wheels at the same time.)

CAUSE
This concern is caused by the EPB being not completely released.
The EPB control module judges that the parking brake is completely released when the current value flown to the motor (A) drops to the threshold, namely when the rotating torque of the spindle (B) drops.
Due to insufficient accuracy of the screw threads of the ball and ramp (C), the spindle (B) may idle momentarily during the EPB release operation causing the spindle rotating torque (the current value to the motor) to drop to the threshold before completely releasing the parking brake.

MASS PRODUCTION CHANGE
The ball and ramp has been modified to improve the accuracy of screw threads.

That’s why I’d go get a pair of new and revised OEM rear disk brake calipers instead of trying to salvage the original ones which have flaws.
 
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yrwei52 said:
The TSB says:

DESCRIPTION
Some vehicles with the electric parking brake (EPB) may exhibit the rear brake dragging resulting in brake noise and the outer disc pad abnormally worn out. Or the vehicle may roll momentarily when starting from a standstill with the EPB applied. (The EPB is not automatically released for both wheels at the same time.)

CAUSE
This concern is caused by the EPB being not completely released.
The EPB control module judges that the parking brake is completely released when the current value flown to the motor (A) drops to the threshold, namely when the rotating torque of the spindle (B) drops.
Due to insufficient accuracy of the screw threads of the ball and ramp (C), the spindle (B) may idle momentarily during the EPB release operation causing the spindle rotating torque (the current value to the motor) to drop to the threshold before completely releasing the parking brake.

MASS PRODUCTION CHANGE
The ball and ramp has been modified to improve the accuracy of screw threads.

That’s why I’d go get a pair of new and revised OEM rear disk brake calipers instead of trying to salvage the original ones which have flaws.
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I will for sure inquire about it. My pads looked exactly like the ones on the TSB with the one inner one way worn down so I think I was impacted by this flaw. For now, I'm happy I have a driveable vehicle to at least get it to the dealership.

One last issue... When I apply the EPB I hear the motors engage and I can verify by trying to turn the wheels that they do engage and disengage. However, when I engage the parking brake with the car on the red parking brake symbol flashes and the yellow parking brake warning comes on. The yellow light on the EPB lever also flashes and the warning guidance just indicates "Parking Brake Failure". I can disengage the parking brake and all warnings disappear. Probably just going to take it in to Mazda at this point now that I can drive it but hopefully I can show them my pads and convince them to cover part of the costs...
 
dpvu said:
I will for sure inquire about it. My pads looked exactly like the ones on the TSB with the one inner one way worn down so I think I was impacted by this flaw. For now, I'm happy I have a driveable vehicle to at least get it to the dealership.

One last issue... When I apply the EPB I hear the motors engage and I can verify by trying to turn the wheels that they do engage and disengage. However, when I engage the parking brake with the car on the red parking brake symbol flashes and the yellow parking brake warning comes on. The yellow light on the EPB lever also flashes and the warning guidance just indicates "Parking Brake Failure". I can disengage the parking brake and all warnings disappear. Probably just going to take it in to Mazda at this point now that I can drive it but hopefully I can show them my pads and convince them to cover part of the costs...
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Honestly, the TSB means nothing to you since you don’t have new-car warranty and this job would be costly from a Mazda dealership. Go get a pair of new calipers online (see TSB for the parts needed with correct part numbers) for lower price, check the date code on new calipers making sure they’re revised version (see TSB), and put them on by yourself following the procedure of Mazda Factory Workshop Manual. If after everything been done correctly with new revised calipers and you still get EPB warning lights, try to get into maintenance mode and out, and may be a battery discount reset, and see if you can clear the warning lights. If you still can’t, then go to Mazda dealer to reset the EPB control module that should do it.

Not sure if you have read this helpful thread by tomcat1446:

Maintenance Mode for 2016 / 2017 CX-5 electronic brakes
 
Bringing this mofo back from the dead b/c I was the idiot who engaged "rear brake maintenance mode" AFTER I removed the rear caliper, and yes, the caliper piston came out all the way and would not thread back in.

The solution: Disconnect the EPB motor from the caliper. Use needle nosed pliers or that fancy brake tool with the notches that fit into the piston slot to rotate the piston counter clockwise while applying pressure. The piston will rotate all the way back in. Be sure to rotate the piston so the notch lines up with the bump on the brake pad. Re-install EPB motor, button everything up.

Took me a bit to figure out that I could safely rotate the caliper piston once removing the EPB motor after reading the many warnings earlier in this thread about not rotating b/c of the risk of damaging the EPB motor itself.

I didnt take any photos or videos, but it's pretty self explanatory. If anyone else has this problem, you're not alone, and it is fixable with regular hand tools.
 
RL911 said:
So what’s the consensus on the proper tool to compress the piston back into the caliper? Plan on using it across several vehicles. Not a huge fan of the c clamp since it’s not quite as precise applying force on the piston And it’s a bit clunky
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Firstly, you cannot compress the piston back into the caliper if you engaged maintenance mode after removing the pads or removing the caliper. The EPB motor will have pushed it all the way out and you cannot push it back in.
Secondly, the piston is physically attached to the motor, so even if you just remove the caliper and pads and didn't engage maintenance mode, and try then to push the piston in, you can't.
Worse: some people think it's old tech and try to turn the piston to get it to go in. That's a big no no.
I suggest you read the other threads on what some people did after messing up the rear brake job.
In a nutshell though, if you engage maintenance mode properly, the EPB motor will pull back the piston and allow you to do the brake job.
 
Thx. I’m aware of maintenance mode, just didn’t realize it retracted the piston fully. Thought it only allowed the piston to retract.
 
The nice thing about this system is that after retracting, the motors will set up the clearance for any thickness of pad so you could service the brake half life and then it uses back pressure to determine the pad thickness.
 
RL911 said:
Thx. I’m aware of maintenance mode, just didn’t realize it retracted the piston fully. Thought it only allowed the piston to retract.
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Unfortunately, the piston cannot be pushed or retracted manually (more on that in a moment). The motor assembly is directly connected to the piston so any attempt to compress the piston will be met with resistance.
Now, I haven't done this myself, but....you should be able to manually retract the piston by removing the motor assembly. That gives you access to the back of the caliper. Apparently you can then turn the mechanism with a screwdriver (clockwise I'm told) that will "pull" the piston back into the caliper.
Again, I have not done this myself, but my son has a BMW with the same system and he and a techy friend did exactly that with the rear brakes on his 2017 X1. They did not activate service mode, and got it done that way with no problems. It should be the same process on the Mazda.
Disclaimer: if you try it this way, do a little more research before going ahead. I don't want to get blamed if something goes wrong...:cool:
 
pbesong said:
Well that didn't go too well. I ended up finding a youtube video on manually resetting the electronic brake here: https://www.youtube.com/watch?v=wAB43eO7wIs and it allowed me to reseat the piston, however I could not get it down far enough to span the new brake pads. All I could do was to put the old rotor and brake pads back on till I can figure it out. At least I can drive it now. The procedure in the video is the same for the Mazda, instead of torx screws they use allen bolts and a hex-headed adjuster bolt. I wound the adjuster bolt all the way down till it stopped and compressed the piston as far as I could but it wouldn't budge after it got down to about 3/8" from where I needed it to go. Just could not fit the caliper over the new pads for anything

The brake maintenance mode light will not turn off either. I tried holding the switch down and foot on the gas while hitting the start button 3 times twice, but it won't turn it off. Tried resetting it into maintenance mode again, then trying to turn it off, but that didn't work either. I can drive the car, but the emergency brake light keeps flashing and it's still in maintenance mode. pissing me off. half hour job is turning into a nightmare. Any help gladly accepted!

I'm also going to get that compression tool as I don't think the C-clamp is probably a good idea being that I had to attach one end to the plastic housing of the EPB. Ended up making my own tool to use for tonight.
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Did your problem got resolved? I am having the same exact issue.
 
yrwei52 said:
The fancy brake tool set with many adapters you linked is mainly for the rear disk brakes also used by mechanical parking brake. The adapter needs to fit the size of the caliper piston, and 2 dots on adapter are to fit 2 holes on piston to turn it while pushing the piston into the caliper. You can also rent this brake tool set for free from AutoZone even if you dont get pads from them.

But for rear disk brakes with EPB on 2016 CX-5, you dont turn the piston while pushing it into the caliper, or the internal components may get damaged.

Read the warning in official Mazda document I posted earlier.

ABN_brake_caliper_tool_md.jpg
So if you have a wrench, you can move the large nut down. It won't spin the shaft but push instead.
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