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Discussion Starter #1
I forgot about this until now, but I noticed when changing my rear pad wear sensor that the rear caliper was wound all the way back, there was no budging it at all with my wind back tool and I checked both the dash and the spring position that the EPB was definitely disengaged.

I use the icarsoft EPB service mode when doing the rear brakes which released the EPB and when you activate it there is a ratcheting noise for a second or two from the rear brakes. Is it possible that it is also winding back the calipers and is this even possible for the car to do via diagnostics? I can't see how but would anyone here know?
 

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I tried that on mine and assumed it did the same when I saw the option, but I still needed to wind it back manually.


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I still had to wind mine back, I thought you always had to.
 

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Yes i wound then back manually too. I’m looking forward to the F-Type rears as they’re push in like the fronts.
 

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Discussion Starter #5
I guess my rear pads must have not worn down much then, they are fairly new. Oh well, would have been handy! lol
 

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I also have the iCarsoft LR V2 and used it when servicing my rear brakes. I found the same as the others, you still need to use a wind back tools after releasing the EPB.
 

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Discussion Starter #7 (Edited)
Does anyone know if it's something which is technically possible, whether it be a Jaguar or any other car? I've never come across such myself, but wondering if the mechanics and electronics are there to remotely wind back the rear caliper.
 

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As far as I can figure out all Jag rear brake pistons that wind back MUST be manually wound back and there is no auto way of doing so, and conversely all more recent models with twin EPBs mounted on the calipers and "EPB service position" functions you don't even push them back let alone wind them back, you just invoke the service position and the leccy motors on each caliper then move the pistons all the way in. Two things I am not sure about though - when the leccy motors move those pistons in do they turn/rotate/wind the pistons or do they just push/pull them, and can you if you want or need to manually push the pistons in?
I have not yet needed to try this and in fact I have never invoked the EPB service position on the F-Type as the only time I changed the rear pads was when I also fitted new 386 mm calipers and the pistons were already fully wound in.
 
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I've stripped the rear brakes down myself right down to the mechanism that activates the parking brake. There's absolutely no way they can be retracted by any other method than winding them back.

It's a screw thread inside which is pushed in an out mechanically, but the pressure of the hydraulics unscrews the piston out to get the initial bite/position of the pads. The only way you can get the piston back is to screw it back on the thread the other way.

The actuating cable will only put tension on, but once it's put in service position it'll just go slack.

I'd also never recommend stripping them to the extent I did, they're an absolute pain to get the cone spring retainer back in!
 
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As far as I can figure out all Jag rear brake pistons that wind back MUST be manually wound back and there is no auto way of doing so, and conversely all more recent models with twin EPBs mounted on the calipers and "EPB service position" functions you don't even push them back let alone wind them back, you just invoke the service position and the leccy motors on each caliper then move the pistons all the way in. Two things I am not sure about though - when the leccy motors move those pistons in do they turn/rotate/wind the pistons or do they just push/pull them, and can you if you want or need to manually push the pistons in?
I have not yet needed to try this and in fact I have never invoked the EPB service position on the F-Type as the only time I changed the rear pads was when I also fitted new 386 mm calipers and the pistons were already fully wound in.
This guy did it manually. And you can put the EPB in maintenance mode without anyting plugged in.

 

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Discussion Starter #11
I wonder why the epb makes such a noise when being put into service mode compared to simply using the button in the cabin?
 

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'Cos it is running further?
 

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Discussion Starter #13
'Cos it is running further?
I would have thought the normal operation of the EPB would be the full travel as well though? I suppose next time I'm at the rear brakes I could try each method and look at the spring mechanism.
 

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I would have thought the normal operation of the EPB would be the full travel as well though? I suppose next time I'm at the rear brakes I could try each method and look at the spring mechanism.
No, it's calibrated to just release tension off the pads, there's no need for it to run any further as it would take 2-3 seconds longer each time to apply if it ran it's full travel.

It probably is worth doing every now and again though to keep the cables clear of crud as they can stick after a while of only doing short movements.
 

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Discussion Starter #15
No, it's calibrated to just release tension off the pads, there's no need for it to run any further as it would take 2-3 seconds longer each time to apply if it ran it's full travel.

It probably is worth doing every now and again though to keep the cables clear of crud as they can stick after a while of only doing short movements.
How does it detect the tension, is there a sensor somewhere?
 

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How does it detect the tension, is there a sensor somewhere?
Wee solenoid or switch that registers increase or decrease in hydraulic pressure.....? By my own standards, that is NOT a bad guess, mins.....! Lol.
 

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How does it detect the tension, is there a sensor somewhere?
Probably judged by the electrical load on the motor I'd guess.
 
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Wee solenoid or switch that registers increase or decrease in hydraulic pressure.....? By my own standards, that is NOT a bad guess, mins.....! Lol.

It's not hydraulic, the parking brake is mechanically operated using a lever system inside the caliper. A wire rope/cable is connected to the caliper from the parking brake actuator which is just above the rear diff.

I too would go with pete's suggestion that it's based on load on the motor. Given that it can also be dynamically applied while on the move in an emergency. I can't remember the exact figures but it's something like 70% above 30mph and 100% below 30 mph. It wouldn't be pleasant however, but neither is having no brakes at all.
 

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How does it detect the tension, is there a sensor somewhere?
There's a hall effect sensor, in the EPB unit, I think it's used to sense the magnetic field generated by the motor ( and hence torque ), probably as a fail safe to current measurement in the EPB control module so it can warn if the brake hasn't applied properly even with wiring/motor faults.
 

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Discussion Starter #20
Ah that's right I mind that emergency use, I think it gradually applies until you come to a stop.

Well, good to learn a few things.
 
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