Wow, that is grasping at straws. Has it really come to quoting random sentances out of context? Really? I know this is the internet Sid, but this is hardly Facebook. I don't understand your motive here?

As I have already quoted three times now, from the very first reply to this thread:

A simple answer to a simple question. I think that is very clearly written, and follows the guidance given by Jaguar to the letter. I emphasised the words you seem to be confusing with "remove".

Simply releasing the park brake using the cabin switch will not release the cable enough to fully rewind the adjuster screws unless the pads/discs are very new and barely worn. The lever will not be fully retracted. That is why a service reset procedure exists, where the actuator/motor will extend the cable until the lever is fully at rest and then you can rewind the screw+piston all the way back in. There are ways to trick it into working by directly powering the motor (Jaguar refer to it as an emergency release only to be used when the system has otherwise failed), but both techniques are quoted above. If you do it with the lever still holding the cable under tension then you risk damaging the gears in the motor, and you are turning an effortless rewind job into an effort requiring herculean forearm muscles. The risk is well described by Jaguar in their own words above. If you want to see the damage that can be caused first hand then buy any of the many used motor assemblies on eBay that have not come from cars being broken and open it up. They are being shifted for a reason.

The last two paragraphs in my reply are advice/tips that will assist when actually changing the pads. Paragraphs are often used to indicate to the reader that there is a logical break in the writing, and the start of a new section or theme. As you say so succinctly, I would expect most people to have understood that, but I do apologise for getting that wrong.

I like cats, particularly orange ones.

The physical action of removing the caliper from the brackets requires you to temporarily relocate the caliper, and the way Jaguar advise in their training is to tie it to the top of the suspension. There is a cast nib there for you to cable tie it so it does not move. You cannot do that without removing the park brake cable from the caliper because it is not long enough to reach. That requires you to remove the round plastic retaining clip which has often seized up because brake dust/road dirt gets in behind the clips which can be freed with WD40 or similar.

You will note that the paragraph above has nothing to do with my love of cats. This punctuation lark is easy isn't it?

This has been done this to death now. Unless you or another member has an question, then I have more important things to spend my free time on than repeating the this verbatim until the end of time.

 

Still curious here.

When I release the EPB manually, the cables go completely slack and the actuator lever goes to the fully released position, that being a mechanical stop on the caliper. As I wind back the pistons, the lever remains on it's stop. There is no binding of the cable or any resistance felt, beyond what would be expected from pushing the brake fluid backwards.

What additional benefit would the OEM computer have?

 

Is that on your 2003 S-Type, Mikey? If you would PM me with the last 8 characters of your VIN I will look up which system it has fitted and check the WSM and bulletins for that vehicle to see if there are any notable differences. I think they are the same though because the EPC shows X350 parts fitted from M45255 onwards. (Was M45255 the mid-production facelift for the S-Type, or the launch?)

I know the calipers fitted to the S-Type (and pre 2006 facelift X350) were totally different, and obviously the SC versions had a separate Brembo park brake caliper on those, but the motor-side is largely the same AFAIK without looking into specific models. That (and your description above) may suggest that the levers on the earlier calipers would be fully released with a normal switch release. With your VIN I can check the service procedure. That could be either the EPB module software is different allowing for a greater release, wear to the motor gears, or age-related play in the cables (they do lengthen over time and need recalibration, which is why the tension should always be recalibrated after every pad/disc change or service).

If you park the car against a wall with the window open so the sound will bounce back and apply the EBP and then release it a few times, do you hear the motor gears at the end of the release sequence? You should hear them clicking at the end of the apply sequence as the module monitors the current drawn for about a second to ensure the motor cannot get any more tension before it disables it, but on the release you should not hear any clicks, just a smooth motor running sound. If you can hear clicks then the EPB needs recalibrating by disconnecting the power to it (or the battery) and then reconnecting and following the prompts given on the instrument cluster. If it is still audible at the end of the release after a recalibration then something may be wrong with the motor gears like some broken or worn teeth, etc.

 

Was looking for a short answer to my question, not a dissertation in which I can find a good half dozen technical inaccuracies.

Never mind.

Poor OP probably regrets asking the question.

 

Man, did this discussion go SIDEWAYS!!!




FWIW, here's the way I see it......the "adjustable pistons" on the calipers appear to be compensation device, for brake pad wear, on calipers that use the brake pads, for parking brake actuation. As the pads wear, the pistons have to extend more, to develop the appropriate force to hold the car. The pistons can only extend so much in the bore of the caliper, before they'd pop out of place. This is where these "extending pistons" come into play. Something or other causes the pistons to "extend" as the pads become thinner, generating the necessary force to hold the car.


My '09 XF has these pistons, my late, great '12 XJ had them, I'm pretty sure that my '16 XJ has them, and even my former '00 Lincoln LS, a cousin to the XF, had them. My Corvette and Jeep Grand Cherokee, however, do not have these pistons, as they use a different e-brake system. The 'Vette and Jeep have an "inner brake drum" cast into the rear rotors, and a pair of shoes press out against the surface of the drums, when the brake is actuated.

 

Ok, I am going to ask a silly question and hopefully I am just not being blind to this information. I see where some have used the "emergency brake rewind" procedure where you install a switch and manually drive the EPB actuator until it is at the full release position. My question is "Where did you get the switch?". Looking online, I am not directly seeing it. I can see via the diagrams that I have what would be needed to manually drive it (2 pins on plug B, 2 pins on plug A). Then it is a matter of simply getting the temporary switch I make up to control the power accordingly. Did you guys make your own switch assemblies or is there a manufacturer that we can get these switches from. If you made your own, do you simply slide some pins into the plugs or did you find the matching plugs to connect up to the OEM connections (if so, who did you buy them through?).

On a side note, I saw something on Youtube that got me thinking that once I locate the EPB actuator, that it may be possible to simply remove a portion of the EPB actuator and manually drive the release mechanism to the full release point. Granted, this would have to be done with the battery disconnected to 1) not cause the motor to start and be a hazzard to the person working on the car and 2) to force a recalibration of the system once the brake work is complete.

Waiting to hear back.

 

Reading your post a couple of things come to my mind.
(1)To remove the caliper in order to change the pads you have to find a way to back off the EPB beyond it being off/released, some may disagree, but to my mind that's what jaguar requires and if there's a lip on the rotor, likely if the pads are worn, then its seems necessary. To back off the EPB you can use SDD, if you have that capability, and it seems to me that's the way to go. Jaguar do mention a standalone switch/module that is connected to a module in the trunk - I expect this would be expensive for its limited use. Then XDave has suggested a means of reversing the power to the actuator.
(2) Once the caliper is removed the piston has to be retracted into the cylinder to allow for the new "thick" pads to be fitted. This can be accomplished using a tool to rewind the cylinder back into the caliper. I have borrowed a caliper retraction kit from Autozone which works and free of charge . I am not aware that you can use any of the options in point 1 to accomplish that.


I found this XF post to be helpful fyi https://www.jaguarforums.com/forum/x...job-how-85582/

 

hafren, I realize that I will need to push the caliper piston in once I get the EPB actuator fully released (I have one in my tools in my garage). My question comes back to where I can find that switch assembly. The switch assembly is what reverses the power to the actuator (as XDave refers to), allowing it to release itself fully.

Unfortunately, I don't have access to an SDD computer at the moment. So, I am looking for the alternative method. But, the switch assembly seems to be an elusive bugger unless I buy it from the dealership (would be curious if they even sell it). I have found a few modules on e-bay that say they will fully release the EPB actuator by plugging into the OBD port. I would just need to do some research into these to make sure that they would work with a Jaguar. These seem to run about $150.

 

Now I cannot confirm without a doubt, but I have never seen my tech have to use any electronics to replace the rear pads. IMHO if the EPB is not actuated the cable and paul should be fully released so piston puck retraction with a tool should not be an issue.

 

If you read what leadfoot4 and XJsss are saying , it really doesn't matter where the cable is sitting or the position of the lever , WHY , because the piston has a spiral thread that when turned ( clockwise ) has no where to go but back in the caliper.

Thermo , stop looking for that " alternative method " it does not exist

Even if you could reverse polarity the EPB , it does not retract the piston , you have to do that manually , the lever can only go as far as it's stop point (which you know anyway) .

However if you own a VW , AUDI or VOLVO , the EPB is built directly into the caliper itself , no cables are used . That where you use the reverse polarity if you wanted to .

Cheers ,

 

Chris,

No extra switch required. Use the existing switch on the centre console. From page 72 in the owner's manual:

The switch which operates the parking brake is
mounted on the centre console to the rear of
the gear selector.
To disengage the parking brake (1): With the
ignition system on or with the engine running,
apply the foot brake and press the parking
brake switch down.

Just keep the switch pushed down while shutting down the car. The EPB will remain off.

Easy-peasy.

 

So, let me get this right. To replace the rear pads (lets assume the piston is extended as far as it can go for a worst case situation), all you have to do is disengage the emergency brake normally and get the car shutdown. This will then put enough slack in the e-brake cable that you can do what is necessary to replace the pads (pushing the piston back in using the mechanical push in tool). Then, once the new pads are on, you do the calibration procedure to reset the EPB module to learn the new pads.

This is not necessarily what I was getting earlier. Maybe I was reading things wrong. What I was getting is that there was "minimal movement" of the cable during a normal release and to get the e-brake mechanism to back off enough to allow the installation of new pads, you had to force the actuator to go further than what it would normally during a normal e-brake release.

 

Almost. The piston gets screwed back in, using the appropriate tool. Pushing alone will either get you nowhere or will damage the caliper.

That's what one poster was getting at, but no one else seems to have had the same experience. Since normal release of the actuator allows the caliper levers to reach their stops, there would be nothing to be gained by further releasing the actuator.

 

Mikey, thanks. Got it now. Guess I will be doing a brake job here in the near future after a day of work. The more I looked into it, the more difficult it seemed to be getting and was making me start to wonder as a brake pad replacement should not be that difficult.

 

That is correct. Keep in mind, that the piston "unwinds" (but 'm not quite sure how) to compensate for the wear on the pad. Therefore you'll have the same amount of clearance when the piston is extended and the pad is worn, as you have with the piston fully retracted, and a brand new pad, assuming, of course, that the parking brake is disengaged.


However, as someone mentioned, it the rotor is heavily worn, and there is a significant "lip" around it's outer edge, there might be a bit of a problem, HOWEVER, the piston can still be retracted into the caliper a little, by hand.


Absolute worst case, if your rotors are THAT worn, you should be replacing them anyway, so your only goal is to get them off the car. Therefore, you COULD take a hand grinder and grind down the lip, for about 30% of the rotor, then rotate that portion of the rotor so it's within the caliper, and that should give you the needed, additional clearance, to remove the caliper.

 

All, just completed the pad change on my car. All the worrying is for not. Moved the car in my driveway to get it where I needed it and didn't set the e-brake. That left the e-brake fully released. From there, you undo 2 bolts and the caliper comes off (don't forget to remove the spring on the outside). From there the piston winds in with no problem. The install is simply taking things in reverse.

I did notice a few things and others might find this of interest:

1) you do not need to reset the e-brake computer like was mentioned above. If you are questioning the need to disconnect the battery/use a special reader, you have an option. I did not do anything to the computer, but after putting the pads on and mounting the caliper to the car, I used a large flat blade screw driver. I placed it between the upper bolt and the e-brake lever (end opposite the cable). From there, you can manually actuate the e-brake by using the screw driver as a lever. This will take up any play that may be in the caliper/pad assembly. Once the pad is against the rotor as you manually do the e-brake lever, the computer will not know the difference (atleast in my case it didn't). Pre-adjust the e-brake mechanism before you apply the e-brake from inside the car and all will be good.

2) something I noticed with my car is I was starting to get a "pad worn and it is eating into the rotor" sound (that metal on metal sound). Inspection of the pads and the rotors showed that this was not the case. What the sound was created by was the fact that the rotor was just starting to touch the worn pad indicator. This noise was normally only present after the car had sat for say 24 hours. After a few brakings, the noise went away. So, keep an ear out in the morning as this may be a way to tell if you have a brake job coming up in your near future. I managed to get 63K miles out of the factory pads (if someone was interested).

3) the wear indicator. What a PITA that little device is if you don't know the trick. I thought you simply had to push the 2 ends of the clip together and that would give you enough room to remove/insert the wear indicator. TRUST ME. That doesn't work. In short, use a screw driver and pry the metal clip from the pad. At that point, the wear indicator can be removed. With the new pads, pull out the metal clip, insert the wear indicator and then push the clip back into the pad.

4) pay attention to the caliper unwind tool that you get. The one I rented was able to do the job, but the only piece that would do what I needed really didn't fit. It was just that tidbit too big to fit into the holes in the piston. So, it made winding the piston back in a little challenging. So, pay attention to what you get and be ready for a little bit of work if things do not fit just so.

 

Well done Chris!

Next time- or for others, no need to ratchet the lever back and forth. Sit in the drivers seat and slowly push the brake pedal as many strokes as required until firm resistance is felt.

The rear brake pistons and EPB mechanism have now been pushed fully into their correct position and EPB recalibration will most likely not be required.

Other have gotten themselves in trouble by trying to calibrate the EPB without first pumping the foot pedal. The actuator will over extend and cause a fault.

 

Mikey, maybe this caliper is different than others I have worked on, but others have 2 separate actions. You have the piston that moves in and out, then you have the action of the e-brake mechanism. They somewhat work independent of each other. So, if you pump the brakes a few times, yes, that will push the piston out to where the pads will touch the rotor, but the e-brake is still sitting back where the piston started and therefore when you "engage" the e-brake, the first few times it will engage all the way and still not apply pressure to the pads to do the e-brake job. After a few cycles, yes, the e-brake will have finally positioned itself to apply pressure with only the e-brake actuator. That is why I say to cycle the e-brake lever a few times to bring the e-brake in line with where the piston is actually sitting. This is why you have to spin the piston numerous times to get the piston all the way back into the caliper body. If the e-brake mechanism simply followed the piston, then you would be able to push the piston straight in.

 

Fair enough.

 

1. So am I to understand from this that you did NOT need a special EPB tool to retract the pistons on the rear calipers to replace the pads? (God, I hope so.)
2. What is and where did you rent the special tool to retract the pistons? I'm gathering from this that a C-clamp is NOT the method here.... Some type of twisting tool is required, yes?
3. Where did you source your brake pads? Seems Jag pads are hard to find in the typical auto parts store. Ceramic or Semi-metallic?

Forgive the "newbie" questions. I inherited my 2015 XJL and experiencing a bit of "sticker shock". I'm all about DIY, but still in the learning phase on the maintenance basics of this vehicle.