Folks,


I'm new and did not think I would need your help so soon. I am doing a job on the rear axle (which I have performed on many other vehicles, some with screw-in pistons as well). I've read other posts on this forum, purchased new pads and rotors (well worn), I held the parking brake button down as I turned off the engine and removed the key. So, I have a double-pinned tool and as I turn the pistons to the right, counterclockwise, nothing happens; driver's side or passenger side. If I turn the piston slightly to the left, they do start to back out, extend. What gives? Do I have thestill on? I've tried applying some pressure against the pistons as I turn them, nothing, nada. The driver's side piston rotates but is much stiffer than the right yet results are the same. One more bit of info; the pads were extremely worn, 0.020-0.030" on outer pad and just about down to the metal on inside pad (meaning the pistons are quite extended).
Thanks in advance for your help.

 

Folks,
I've re-posted to make this more readable:

I'm new and did not think I would need your help so soon. I am doing a simple brake job on the rear axle. I've read other posts on this forum, purchased new pads and rotors (they were too thin to be re-surfaced), I held the parking brake button down as I turned off the engine and removed the key. So, I have a double-pinned tool and as I turn the caliper pistons to the right, counterclockwise, nothing happens; driver's side or passenger side. If I turn the piston slightly to the left, they do start to back out, extend, then I turn them to the left and they retract a fraction and just spin. Is the parking still on? I've tried applying some pressure against the pistons as I turn them, no change, nada. The driver's side piston rotates but is much stiffer than the right, yet same results. The pads were just about down to the metal backing (piston quite extended).
Thanks in advance for your help.

 

Ah- now I follow. I ran into the same issue. Apply more inwards pressure as you turn. Think of an ex-wife if it helps build adrenalin. Alternatively, open the caliper bleeder.

All will be fine.

 

Don't wind the pistons back too far, i.e. just far enough back to get the new pads in.

If you wind them all the way in the calibration of the park brake end stop will be out.

My mechanic didn't listen to me about this, wound the pistons all the way in, and when he put the park brake on it jammed on because the motor went past it's end position.

Officially you need to use the IDS/SDD diagnostic system to set the park brake in a "service position" which as far as I can tell is winding the park brake motor as far back as possible.

 

I've not had to work on my rear brakes yet but:

With most disc handbrake systems, after reassembly you need to pump the brake pedal hard a few times to reset the automatic adjuster - BEFORE using the parking brake for the first time.

 

Mikey, Cambo351, & Richard,


Thanks for the help. I wasn't able to turn in the piston without opening the bleed screw, I guess I'm getting weak in my old age. With the bleed screw open, it backed in just fine, with good pressure applied. I did not think to do this for I've always just pushed the fluid back into the reservoir. Maybe something different about these brakes because it was a no-go with the bleed screw closed. To ensure I didn't back in the piston too far, I measured the thickness of the new pads & rotor (2 1/8" in my case) and backed in the piston until I had that much clearance between the piston and the support bracket (where the outer pad seats). I bled the brakes and pumped them several times before and after starting the car (for good measure) and all is fine. No EPB fault, good quiet brakes and parking brake works.
Thanks again.

 

WTG Charlie.


I have done 3 rear S Type (3.0's) brake jobs.


One 2003 that I could barely turn the rear pistons in, it took a lot of force without backing off the bleeder and 2-2005's that I could basically turn the piston back in without relieving the bleeder by hand.

 

When I did the rears on our '05 STR the LR twisted in fairly easily. The RR required quite a bit of inward pressure while twisting. It finally retracted though.

I also made the mistake of winding them all the way back... Got them all put back together and, EPB Fault. Grrrr.

Disassembled again and wound out the pistons until the new pads just fit, re assembled and all was well.

Cooper

 

It's not necessary to disassemble. The calipers are self-adjusting. With the engine running, repeatedly apply the foot brake until the pedal no longer sinks to the floor and now has a 'normal' feel.

If the EPB issues a fault, follow the factory calibration procedure which takes maybe two minutes.

 

I'll be replacing my 2005 S-Type 3.0's almost-shot rear brake pads next week once the new pads I ordered from rockauto.com show up in my mailbox, so I'm very glad I found this thread. I appreciate the valuable tips here of not winding the rear pistons in too far, and being sure to pump the brake pedal back up to typical pressure once the new rear pads are in place before starting the engine and recalibrating the EPB system....

My JTIS instructions are fairly straightforward but there is no mention of not winding the pistons in too far to stay out of EPB trouble. Thanks to all who contributed to this thread. Had I not found it, I'm sure I would have wound my rear pistons in all the way since I am accustomed to pushing the conventional pistons all the way into the caliper with my trusty C-clamp....

I'll be using one of the brake caliper piston kit loaners from Autozone or Advance Auto Parts so I hope one of the various disks in the kit will fit my rear pistons perfectly. We'll see....

I wonder why our S-Types have these spin-and-push pistons on the rear axle. Our S-Type front axles have the conventional pistons and all you need is a C-clamp. My wife's 2006 XK8 has the conventional pistons on both axles. So why did Jaguar muck up our rear axle brake systems like this (other than to add a higher degree of difficulty to doing our own brake pad replacements at home)?

 

It's not mentioned because it's not a concern if the entire replacement procedure is followed correctly. The foot brake must be exercised bringing the new pads into contact with the rotor before any attempt is made to recalibrate the EPB.

This is a very common design where the service/foot brake is combined with the emergency/parking brake using a common caliper and pads. The foot brake is hydraulic, the EPB is mechanical. Each system requires a method of compensating for brake pad wear and keeping the clearance between the friction surface and the rotor at a minimum. The screw-in feature is roughly equivalent to the mechanical adjusters found on drum brakes. The same as drum brake adjusters were mostly self-adjusting, so is the mechanism for the EPB.

 

The Brembos are different - just the push-in type - but that's why there's then a separate EPB caliper. Has to be more costly (but then Brembos are - so I suppose I mean even more costly!).

 

I would prefer to have conventional rear brake pistons, no EPB system, and a manual handbrake lever like my wife's XK8 has. Having to replace my failed EPB module back in June at considerable expense further increased my dislike of these EPB systems....

 

Whether the parking brake cable is actuated upon by your hand pulling up on a lever or an electric motor and gearbox does not change anything about the caliper.

Same-same.

 

Jon, as memory serves me correct here. I did not follow JTIS at the time with the 2005 MY's. I basically took the "cube" and rotated it back into the caliper (sorry cannot remember which direction) by hand. I do remember that I retracted the piston to the point they were "flush" with the caliper, inserted the new pads and reassembled without any problems. Followed the recalibration of the EPB and poof, Bob's yer Uncle!

Joels '03 MY was the difficult one.

You know my number if you have questions or problems, which you won't.

 

" Mikey " is spot on with his explanation of piston depth retraction , though
nobody appears to be listening .

 

Au contraire, I'm listening to everyone who has contributed to this thread since I have never personally done a pad replacement on a spin-and-push-type brake caliper piston before. From the comments posted here, I still think it's wise to retract the piston only as far as necessary to fit the new pads. Why ask for trouble when there's a simple way to avoid it?

 

Because the 'just enough' process doesn't avoid the problem unless you're exceptionally lucky. You'd have to assemble/take apart/assemble/take apart an unknown number of times gradually turning the piston until the pads are just far enough to slip over the caliper. It's possible/probable at that point that they would be just half a hair too far apart and the problem outlined above with the EPB actuator being over extended would occur.

The chances of getting it right are the same as having a firm high foot pedal right away with no pumping required.

Much easier doing it the OEM way which also guarantees success the first time.

 

Does anyone who has already replaced their rear brake pads remember which direction the "special tool" must be cranked in order to spin the piston back into the caliper? Knowing that my current pads are no more than a millimeter from being completely spent, my pistons have to be close to full extension and I'm not going to have any margin for error when I begin the process of spinning them back into the calipers....

 

I turned mine clockwise to go in. I didn't have the cube/square, but you still turn the piston clockwise.