When replacing the rear brake pads, I put the car in brake maintenance mode, and removed the old pads without issue. Unfortunately, before re-installing the pads and caliper, I pressed on the brake pedal and extended the piston to the point where I cannot get the caliper on. I’ve tried taking the car in and out of brake maintenance mode several times, but now the piston is quite extended (photo), and I’m getting a warning on the dash to recalibrate the parking brake. The car is currently in brake maintenance mode, and it will not come out of this mode. Is there a way to fully retract the rear caliper so as to complete the pad installation?
thanks
steve

 

I see in the doc I have that there is a manual mode for retracting the piston. You need to remove the actuator and wind the spindle back in. Note the direction of rotation. They don't mention needing to push the piston back in also, but I wouldn't be surprised if it's necessary. Hopefully the piston hasn't come out far enough that the seal is exposed.

 

If they are in maintenance mode you should be able to push them back in normally with any caliper spreading tool, i use a large C-clamp or slip-joint pliers if you can do so safely.

You pushed them out with hydraulic pressure, not the parking brake, if you stepped on the pedal to start the car or whatever.

 

He mentions going out of and back into maintenance mode several times, so I'm not sure that's a valid assumption. It sounds like it was both mechanical and hydraulic.

 

Yes and no, he may well have locked them back into normal mode if maintenance mode was exited, but the pedal press will extend them fully using fluid. Either way he needs to be sure he's in maintenance mode/EPB motors retracted, then push the piston back manually. It will not pull the piston back with the EPB anyway.

 

Thanks for the suggestions everyone. I will try winding back the actuator first, then try compressing the piston. I have tried compressing the piston with a compression tool, using low force, and got no movement. Hopefully I’ll be able to compress the piston having wound back the actuator. If not, it may mean that the piston has extended too far to retract, in which case I’ll try opening the brake line, and if necessary remove the caliper and refit the piston.

Assuming I get the piston back, should I expect that the dash message regarding calibration will still be present, and that I should allow calibration once everything is assembled?
Thanks
Steve

 

b

 

Yes any time you manually move the parking brake you will need to recalibrate, it winds the motors all the way in (released), then engages them until the force increases to a preset amount so it knows it's grabbing the rotor, and it saves the number of turns. Any movement not by the motor loses that calibration.

 

Thanks for info everyone. I was able to manipulate the piston back into the cylinder with only a small loss of fluid. I then retracted the parking brake per the instructions posted, followed by the compression of the cylinder to the fully retracted position using my regular compression tool. The car then did it’s calibration and all seems to be well.
thanks
Steve

 

Glad you got it handled! Good warning to always be careful that nobody can press the pedal while the brakes are apart, to avoid this issue.

On newer JLR products with the IPB system, they can auto-pressurize when a door is opened or for other reasons, so the system has to be put in service mode using the scan tool before any brake work, not just the parking brake issues. Good times.