HELP! Can't get the rear brake piston to compress! 2016 CX5

:
Ottawa, Ontario
:
17 Mazda 6 GT
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.
 
:
2017 Mazda CX-5 GT, 2016 Mazda6 iGT, 2014 Mazda3 sGT hatchback
$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.
 

yrwei52

2016 Mazda CX-5 GT AWD w/Tech Pkg
Contributor
:
Plano, Texas, USA
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.
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
 
Last edited:
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
 
Last edited:

yrwei52

2016 Mazda CX-5 GT AWD w/Tech Pkg
Contributor
:
Plano, Texas, USA
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
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.
 
Last edited:
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.
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...
 

yrwei52

2016 Mazda CX-5 GT AWD w/Tech Pkg
Contributor
:
Plano, Texas, USA
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...
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
 
Top