XJS ( X27 ) 1975 - 1996 3.6 4.0 5.3 6.0

Rear inboard brake caliper change, on car

Old Feb 12, 2023 | 12:32 PM
  #1  
Greg in France's Avatar
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Default Rear inboard brake caliper change, on car

I have always thought that it was just about impossible to change a rear inboard brake caliper without dropping the rear axle cage first. I know some people have claimed to do it, but as far as I know, nobody has ever explained or posted how, if it is indeed possible.
Well yesterday I looked into brake fluid loss which had been slow, but there for a month or so. I am not using the car that much, being winter, but the few times I have, the fluid has gone down more that it should normally. Car up on ramp, looked aroound with No. 2 son and he found it. Rear LHS caliper and the pads soaked with fluid, so a seal breakdown on one or both pistons.
I needed to use the car on Monday, and I could not face a cage removal, so I though I would give it a go, axle cage in car. On a DANA diff car the caliper is undone from the outer side of the disc through a hole provided for the purpose. The hole provided by the manufacturers, including Jaguar OEM discs, is in the wrong place and not big enough. I had my mate "Louis, Roi Des Tours" (Louis the Lathe King) enlarge them for me some time ago when I did my diff and axle work (see thread "DANA differential Demystified).
So this is what I did:
  1. car up on ramp
  2. driveshaft unbolted from diff output shaft studs
  3. radius arm unbolted from chassis at the large bush end
  4. shock absorber lower fixing pin undone and removed; this allowed the lower wishbone and driveshaft to hang downwards, allowing access to the disc. BUT see point 11 below
  5. Caliper feed line from cage central T piece (feeding both calipers from this T) undone and capped to reduce fluid loss. To remove it from the caliper requires both ends to be undone, the the T piece end refitted and the caliper end capped
  6. handbrake cable released from the lever
  7. HB return spring removed from caliper
  8. exhaust pipe over axle section removed
  9. pads removed from the caliper (HB pads not touched)
  10. Caliper bolts undone
  11. tie plate under the diff has to be unbolted and removed or else the lower wishbone does not drop enough to release the disc.
At this point the entire caliper and handbrake assembly is loose and the entire thing, disc and all, can be wriggled free. The caliper naturally drops down a bit and it was heavy on my ancient arms, but otherwise not hard to do. WHHOOPPEE.

Wishbone and driveshaft released

Caliper bolt visible through access hole in disc. Once the hole is aligned with the bolt it can be undone 5/8th A/F

No. 2 son and I had rebuilt a NOS caliper I had in stock with new seals the day we found the leak, so all ready to go. The handbrake caliper was fitted to the rebuilt caliper and the HB pads loosened off a bit using the slotted adjuster (splitn pin removed to do this). Then and this was the hardest prt of the entire job, the caliper is fitted over the disc and the lot offered up so the disc could engage onto the diff output flange studs. Because the caliper tends to drop downwards, it was a strain on the ancient GiF arms but on it the disc eventually went and the caliper was in more or less the right position. The disc prevented it from dropping out.
The caliper now had to be pushed upwards and clockwise so as to align the caliper holes with the threaded holes in the diff casing it bolts to. Not too difficult and 15 mins later it was bolted in place.
  1. next the handbrake adjuster was tighted up so the pads were close to the disc and the split pin inserted
  2. then I refitted the over axle exhaust section
  3. then, using my transmission jack to lift the hub, and No. 2 son helping, we refitted the camber shims (I forgot but realised after one metloc was finger tight, thank goodness!) and the driveshaft to the diff output studs.

caliper exhaust and disc back on, ready for driveshaft

After this it was a matter of attaching the lower shock absorber pin to the wishbone and then refitted the radius arm to the chassis.
Under the car, the feed pipe to the caliper has to be attached, new pads fitted to the caliper, and the rear brakes bled. I have remote bleeders so this is less painful than it used to be. The handbrake caliper lever has to be attached to the HB cable and the return spring fitted. NOTE: once the cable is released from the lever, I have found that it is impossible to get it back in unless you do as follows:
  • someone in the driver's seat
  • me pulling HARD on the cable, using pliers, under the car
  • person in the car pushes in button in on HB lever and keeping it pushed in moves lever up and down. You feel the cable give enough to allow it to be re-engaged in the caliper lever. I have no idea why the cable does this automatic 'shortening' when released from the caliper lever, but it does!
Tie plate refitted, wheel on, road tested, no leaks and all good! Took a day all in.

Disc on, caliper on, ready for driveshaft to be fitted

I would say this is easier than removing the cage, but still hard work, and just about impossible without a lift, certainly for the aging pensioner!
 

Last edited by Greg in France; Feb 12, 2023 at 11:58 PM.
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Old Feb 12, 2023 | 02:22 PM
  #2  
motorcarman's Avatar
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From: Wise County,TX
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That is the way I have done it when a lift is available. I did have to remove the rear suspension when the lift was NOT available.
 
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Old Feb 13, 2023 | 07:57 AM
  #3  
3Jagsplusothers's Avatar
Joined: May 2021
Posts: 40
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From: Efland, North Carolina
Default I did it on my 90 convert - wrote if in Jag--Lovers forum no pix. sorry

This topic has been discussed previously and several folks in years past have posted lengthy and helpful descriptions of the process. I recently finished the job and I thought I would offer (without pictures unfortunately) some of the things I found whilst doing it. Let me say that this is not a job for impatient people. One old pro said that he did it in an hour per caliper. If so, the hand of god must have helped!

I did it with the IRS in place in the car. Fortunately I have a 4-post Backyard Buddy lift which helped immensely. I began by removing the under plate to the IRS. I’m not sure it was necessary ultimately. 13 mm wrenches and sockets did the job nicely.

The bolts holding the calipers in place are very difficult to reach and have a factory-installed wire between them. That was a challenge to get loose, but patience and needle-nose pliers manage the task. Start with the bottom because the twisted ends are there. I did not attempt to reinstall the wires after doing the rebuild. Didn’t see the need for Coventry’s belt and suspenders approach.

I was able to us a 16mm offset closed end wrench to get to the top bolt and a regular 16mm wrench to do the bottom one. I did need to use the boxed side initially and used a cheater to break the bolt free. After that, it’s one flat at a time to undo both bolts. They cannot be removed as there is no room and must stay whilst removing the caliper. I also undid the fluid connection with a 7/16 brake fitting wrench (broke it free and then used a regular 7/16 wrench to finish). It leaked fluid even after plugging it.

The handbrake cable must also be removed by pushing the cable to get it out of the right handbrake caliper lever, pushing the rubber cover off the left cable piece and then slide the whole thing out of the left lever. Push it up and out of the way.

Now the fun parts. I removed the brake pads and retaining hardware (one pin goes in from the left and one from the right…don’t exactly recall which is which, but easy enough to figure out). This made it a little easier to move the caliper and attached handbrake caliper down a bit. This allows (I use that term loosely) to bend the tabs around the handbrake caliper bolts (on the regular caliper) so that you can unbolt the handbrake caliper bolts. An 11mm socket did the job once the tabs were bent back. There are 2 tabs per bolt, but on mine, only the side tabs were utilized. The bolts are about 2 inches or so with the bottom half of them being smooth and unthreaded. The threads are maybe 3/16 or so by the bolt head. They are essentially pins that hold the handbrake caliper between 2 holded elements on the main caliper. Also, there is a brass U-shaped (sort of) clip that is held in place by the pins and the arms of which have ends that are slightly bent and go into holes in the 2 halves of the handbrake caliper. Getting the handbrake caliper to free itself from between the main caliper elements was challenging. After 75K miles, it took a lot of shaking to get them free.

Once free, they can be pushed back up and finagled off the rotor. It’s then possible to wriggle the main caliper up and somehow (it’s like one of those confounding puzzles where this is a simple right way to do it…my brother can do them in seconds…show you how he did it, and you still fiddle around for 30 minutes) get it out.

I then completely disassembled the caliper, washed it in my parts cleaner (I use Pine-Sol in a 50:50 mix with water). Works very well after a soak. I also put them in my media blast cabinet. They came out looking brand new. The build is very simple…an inner seal with Dot 4 fluid, and a dust boot with retaining clip for each side.

The handbrake caliper is also easy to dismantle and clean. Upon reassembly, I used white lithium grease for the adjuster and associated parts. I replaced the handbrake pads (readily available from a few suppliers for about $50). I then measure the rotor and adjusted the arms to that (about 1/2 inch) measure. I also rebent the brass arm to fit the holes in the caliper sides and the pin holes.

Time for reinstallation in the car. With the bolts loosely in the main caliper, I managed to get it in place. Once sort of in and around the rotor, you have to push the bolts out as far as they can go to get the caliper to fit on the bracket. Once there, it’s the handbrake caliper’s turn. Again challenging to get in place, but even more challenging to fit the 2 arms into the main caliper. Patience, rest breaks, and more patience the requirement here. When it finally gets into place, the next challenge is getting the brass piece, the locking tabs, and the pins in place. Remember the brass fitting arms have to go into holes in the handbrake caliper and the pin holes have to line up. Cursing helps a lot…for your spirit, but doesn’t do a damn thing for the pins. Eventually you’ll get it. Bend up the locking tabs.

Now it’s time to get the caliper bolts in place. For me, despite others claiming that the used some wire to line up the holes, I was able to get my hand up to the top bolt and wiggle the caliper around until I felt the bolt slip into the hole. I got a couple of threads in and used the 16mm flat wrench to get it further along. That made it easier to align the bottom bolt (with a screwdriver blade pushing it whilst using the flat wrench. I should also add, that I put the pads in place before this step so that there would be less play.

The next step was trying to get the fluid fitting in place. Another half an hour fiddling with it trying to get the threads to align. Keep taking breaks, swear you’ll come back tomorrow and try again, get off the stool on which you rested while considering when you might return to the task, go back and take another stab. When finally in place, you can reflect on the fact that you have to do it all over again for the other side of the car.

I have to say that the whole process took about a week for me to complete, just because it’s tough with your arms over your head (whether on a lift or on jack stands) and standing on a concrete floor for hours. Reattach the handbrake cable and give the handbrake lever in the car a couple of pulls and releases to set the pads correctly.

When I went to bleed the lines with an assistant in the car, I found that we had to turn on the ignition in order to activate the electric booster. I was then able to quickly bleed the brakes. When I was confident that the job was done, I reinstalled the IRS bottom plate. Brakes work great and I finally have a real handbrake. Ready for another 75K of driving.

Despite the lack of photos (if you can find the other postings from the early 2000s, the pictures are pretty good) I hope this is helpful to someone who doesn’t want to pull the IRS to make the job easier. BTW, I found that the 16mm wrenches worked much better than the prior recommendations (which were non-metric). I suspect that the actual sizes were Whitworth but I don’t have any of those.

Good luck. It’s definitely doable. Beer and/or whiskey might help, but I cannot confirm that.
 
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