I have been doing most of my car maintenance since the 50's. My all time favorite being a 3.8 S that I had in the early 60's. To save you the math I will be 69 in two weeks. Actually the Mk II needed very little maintenance but when it did it was unusual, a front natural rubber suspension mount, a rubber steering universal which was quite exciting when it failed, a transmission dash-pot that needed the front suspension and motor lowered to replace and a few other mundane electrical issues. Three years ago I replaced the front brakes on my 2004 S-Type 3 liter (not an R) non-Bremo brakes in about 2 hours. This is the best car I have owned, I love it.

Yesterday I decided to change the rear pad and Rotors and when I removed the driver's side caliper I learned that I was in for more of a challenge. It was only with difficulty that I was able to get the caliper off! Here is blow by blow of what followed,

1. I tried to compress the piston into the cylinder with my trusty C clamp to no avail, turning to Jaguar Forums I discovered that the cylinder had to be rotated which required a special tool.
2. I trundled off to Auto-zone and returned with tool. Having no understanding how the parking break mechanism is constructed and not being able to find a cut-away drawing I followed the directions that came with the tool and rotated the cylinder clockwise but it did not say how far. 90 degrees? 180 degrees? So, I rotated the piston 90 degrees clockwise and nothing happened. After several attempts with the piston in several positions I was still not able to compress the piston. Then I tried rotating the piston counter clockwise and still could not compress the piston.
3. Back to the Forum and that concerned the parking brake might be engaged, up until now I had been working with the key on and because the cable was not taught I naively believed I had circumvented the parking brake activation.
4. Several posts pointed out how to shut of the off the car and simultaneously disengage the parking brake. Then a big mistake, I thought that if I just tapped the brake pedal I would not have to constrain the piston. Well as you can guess it it moved considerably, luckily it did not pop out but now it is extended 3/4 inch more and I still have no idea how to compress it.

Well I have a three legged Jaguar in my driveway and if I can not find a way to heal it I will have the embarrassment of having a wrecker hauling the car away. Perhaps I can find someone that will pick it up at 2:00am in the morning.

Worse yet, you may find this hard to believe, my better half has listing the reasons I should not do this project for the past couple of days.

So How do I compress the pistons at this point? Anyone have a cutaway? Has anyone had one of these cylinders apart? Any ideas to help me out of this mess?

 

I don't see why it won't just rotate back in (though maybe there's a point it's gone past where that's not true - I doubt it, though). Obviously the fluid needs some place to go and it'll be easier if that fluid has an easy way to go there - I undo the bleed nipple as I like bleeding out old fluid anyway.

Mine are the Brembos but I don't see why the above wouldn't apply to yours.

I suppose you could take the caliper off and work on it off the car. Worst case you buy a replacement (I'd get a used one).

I think yours are the sliding pin type. Lots of help on the net about them - very common on cars over here and I would've guessed over there, too.

 

You need to "screw" it in, just keep turning clockwise until done.

 

That's the key- the piston is threaded and need to be rotated as many turns as it takes to fully retract it into the housing. I forget which direction CW or CCW and whether both sides are the same. Now that the piston has been over-extended I'm not sure if any damage has been done.

How you caused the parking brake to release makes no difference with respect to retracting the piston.

 

Did you loosen the brake fluid reservoir cap to allow the preasure not to build up in the reservoir? The Auto Zone tool will only work in 1 direction to screw the piston back in. On my wifes '05 the piston recessed quite easily, on a fellow members '03 it was an SOB even with the Auto Zone tool.

 

At least on my car both are clockwise, I would assume post-facelift are the same.

 

Try the cap thing but another thing depending on how hard you cranked on it with the C clamp you might have it stuck on the threads now and could of possibly destroyed some of the threads. So if the cap doesnt work try pumping the brakes to use the pressure from the brake system to push it off of the threads then retry pushing them in with the special tool. You may just have it seized up on the threads and that may get them unstuck. If that doesnt work you may have destroyed the threads and you may have to take the caliper apart check it and could at the worst have to buy a new caliper. Try the pumping and see how that goes.

 

I'd strongly advise against any pumping! That's a sure way to pop the piston completely out of the caliper.

 

Thanks a million folks!!
I will start tomorrow
1. Loosen reservoir top
2. Loosen bleed
3. Position Auto-zone tool
4. Turn piston clockwise
5. If it does not move the piston inwards I will assume that it was pushed out past the threads
6. I will then try to gently push it in without rotating to try and engage the threads
7. Then try to push the piston in and turn simultaneously

What do you think? You guys are GREAT! Even if this is not the final answer at least thanks to your help I have some things to try. Also if I really am stopped I’ll take the suggestion and take the cylinder off. That way I can take it apart and see how it works and if it is not damaged push the piston back in.
pistonspeed

 

Good luck tomorrow. No need to loosen the M/C reservoir cap by the way, it's vented.

 

Correct...After going for the same super aggravating problem, I posted the screw method in the S-Type FAQ...

 

I am not sure of the configuration between my 2000 and your 2004 but my procedure might help Jaguar S-Type Brakes

 

Sometimes you just have to really push kinda hard while turning to get them to retract. On some cars you need almost no push pressure and they retract when turning. On others, (like my SAAB), you have to smack your thumb with a hammer to get pissed off enough to then push and turn at the same time in a rage of brute force.

 

If the piston's been moving out such that the brakes worked (i.e. the brake pads actually provided braking), the piston ought to wind back in fairly easily - especially as the wind-back tool can readily provide a fair bit of force just where it's needed. No hammer ought to be needed!

If the piston's stuck such that so much force is needed, I expect it means the brakes weren't working right and you can normally tell when you inspect the rotors. It's one of the reasons to inspect them reasonably often

The OP's one may well be different if it's now out far further than normal, as it sounds.

 

The rear parking brake piston and caliper uses a screw mechanism which is held back by a spring at the back of the caliper. When I was replacing my parking brake pad I ended up in a similar situation after turning the key on unintentionally. With help from a friend we first removed the spring and screwed the piston back then connected it back when it was retracted well enough create space for new pads. I found it much easier to do it it this way maybe there are better ways to do it.

Eventually when you recalibrate after the job it'll reposition to the right setting.

 

He doesn't have the same caliper etc as the 03 STR.

 

How I wish this was always true John, but I've had to push pretty hard on a number of my vehicles, all of which the braking systems were working normally. Hopefully in the OP's case the piston is not over extended to the point of no return.

 

You had to push hard when using the wind-back tool (not cube)? I don't even see how you CAN push hard, since the tool exerts pressure as you turn the lever/handle (struggling for the word). Are you talking about a different kind of caliper or a different kind of tool, one where pushing can be done?

The lever/handle I'm on about resembles the one on a bench vice (vise).

 

Is this the tool you are looking for? OEM/18 pcs. disc brake caliper set (27113) | Brake Tool | AutoZone.com It is available as a loaner at AutoZone and I understand it works.

 

Yes, that's the kind. There are tons of similar ones. Thanks, Gus.