[xj-s] Rear brake rebuild

I have started the process of replacing rear inboard disks and
rebuilding calipers. I chose not to drop the cage, but I have 2
questions.

1- All the manuals have complete removal of the handbrake as the
first step. Is this necessary if I’m not changing handbrake pads?

2- Radius arms!!! I know that’s not a question, but anyone that has
done this surely knows what I mean. Obviously, hitting the radius
arm itself is not going to get it off the hub, the rubber will
absorb the impact. I can hit the inner metal sleeve either at an
angle from below or straight up. Will hitting straight up
eventually help break it loose, or just push it on tighter? I’m
also using Liquid Wrench and a short pry bar to push down on the
top lip of the inner sleeve. Nothing yet. Any suggestions? (Other
than upgrading from a 3 pound hammer?)

I had only minor trouble removing the 4 nuts holding the disk to
the universal. The 2 bolts holding the caliper are fun to get to,
but I did get em loose. You know, this job doesn’t seem too bad…
if I could only get those radius arms off.

Regards,
Tony Evans Omaha, NE
91 V-12 XJ-S Convertible–
tonysxjs
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Tony,

There are many ways to get the front, large radius arm
bushing off the car.

Hitting the center of the bushing on the metal part
from below directly or at a slight angle works. The
object is to deform the tapered bushing center for an
instant so it looses it’s friction/compression grip on
the car. Like Chinese finger toy. Bigger hammer is
better here!

Prying down from the outside between the floor and the
top of the radius arm has been done. It takes a long
pry bar.

Drilling holes in the rubber and tearing off the
radius arm with half the large bushing left on the car
allows various methods: Heating the remaining metal,
cutting the metal with a small cut off wheel or cold
chisel.

Use a gear puller to keep pressure on the radius arm
and bushing while soaking with penatrating oil.
Eventualy it will pop off.

I am sure there are others. I prefer the BFH method.— tonysxjs tonyronin@yahoo.com wrote:

2- Radius arms!!! I know that’s not a question, but
anyone that has
done this surely knows what I mean. Obviously,
hitting the radius
arm itself is not going to get it off the hub, the
rubber will
absorb the impact. I can hit the inner metal sleeve
either at an
angle from below or straight up. Will hitting
straight up
eventually help break it loose, or just push it on
tighter? I’m
also using Liquid Wrench and a short pry bar to push
down on the
top lip of the inner sleeve. Nothing yet. Any
suggestions? (Other

Geoff Green

96 XJ6 X300, 95 XJS 4.0 conv, 61 E-type OTS
International Cabriolet Register Jag92hot@aol.com
3.6 XJS Register paulzimmer@btopenworld.com

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Tony,

When I did mine another lister gave me a hint which I used and it worked just fine.
Take a 2 x 4 and taper the end of it so that you have perhaps a 30 degree wedge.
Then place it between the frame rail and the radius arms and beat it in until the
radius arm lets go. Worked for me without any problems. Good to use a good penetrant
such as PB Blaster (no affiliation) as well.

Good luck.

PS I dropped my cage out when I did mine. The rear parking brakes are a bear in the
car from what I see and they were tough even with the rear cage out.

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In a message dated 3/19/2006 1:47:34 PM Eastern Standard Time, “tonysxjs” tonyronin@yahoo.com writes:

2- Radius arms!!! I know that’s not a question, but anyone that has
done this surely knows what I mean. Obviously, hitting the radius
arm itself is not going to get it off the hub, the rubber will
absorb the impact. I can hit the inner metal sleeve either at an
angle from below or straight up. Will hitting straight up
eventually help break it loose, or just push it on tighter?

Hi Tony:

Hitting the inner metal ring of the bushing, from the top, gets the radius arm off the body spigot in about 5 seconds. Using a cold chisel and hammer instead takes 10 - 15 seconds (at least that’s what my 85 that had the parts in place for 20 years required). Don’t know about the handbrake question as I dropped the cage and took everything apart.

George Balthrop, Clifton, VA USA
85 & 89 XJ-S Coupes; 89 XJ40 VDP

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In a message dated 3/19/2006 7:14:50 PM Eastern Standard Time, @GBalthropXJS writes:

Hitting the inner metal ring of the bushing, from the top, gets the radius arm off the body spigot in about 5 seconds. Using a cold chisel and hammer instead takes 10 - 15 seconds (at least that’s what my 85 that had the parts in place for 20 years required).

What I MEANT to say was: Hitting the inner metal ring of the bushing, from the top, with an air hammer, gets the radius arm off the body spigot in about 5 seconds.

Prying did NOT work for me. It took impact.

George Balthrop, Clifton, VA USA
85 & 89 XJ-S Coupes; 89 XJ40 VDP

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In reply to a message from tonysxjs sent Sun 19 Mar 2006:

Tony
I just did my rear brakes. Leave the radius arms attached to
the car, undo the small end. It’s much easier. The emergency brake
calipers are bolted on the tops of the hydraulic calipers so you
can take them out as a unit per side. The center plate on the
bottom of the cage had to come out in mine to get the lower
suspension arms down far enough to get the rotors out. I was able
to blow the pistons out of three calipers with compressed air but
the fourth was really stuck [be ready for flying parts, dangerous!]
I filled the last one with water, tightened in the two bleeder
screws and put the torch to it. Left a dent in the wall but it
worked. Drop the whole thing with a motorcycle jack. There are
only eight bolts after the brake lines and radius arms come off. It
gives you a lot more freedom to work especially if you have to heli-
coil a caliper mounting bolt like I did.–
Dean Scott
St.Thomas,Ontario, Canada
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In reply to a message from tonysxjs sent Sun 19 Mar 2006:

Tony, Im glad to hear that yet another person is going to
tackle this job. All good questions. I’ve owned my 91 for
about 6 months and am just at the brake bleeding point of
replacing calipers and rotors. should have rebuilt calipers,
but… First, Im not sure about leaving handbrake cals
on. I first removed tie plate, and had just enough room to
get calipers out seperately. secondly, radius arms are a
challenge. I would probably leave them attached to the
spigot at the large end. the drivers side, I ended up cutting
through the rubber, then made a cut through the remaining
cup, spread apart the cut and then it came off. the right
side just pryed off. The wood wedge sounds good. there are
other methods in archives. After I removed one
caliper and rotor, left side, I removed entire cage. apart
from cleaning 15 years of grease etc, reassembly was much
easier. I used a furniture dolly with 3/4 plywood srewed to
top and a rgular floorjack, lowered irs and wheeled out the
side. To remove exhaust I left it assembled from tip to just
ahead of IRS, remove rear shock/ spring, and that whole
exhaust section comes out, and reinstalls without any
problem. Hope its some help…Ken.–
The original message included these comments:

1- All the manuals have complete removal of the handbrake as the
2- Radius arms!!! I know that’s not a question, but anyone that has


cardogs
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Dean Scott wrote:

I was able to blow the pistons out
of three calipers with compressed air but the fourth was really stuck
[be ready for flying parts, dangerous!] I filled the last one with
water, tightened in the two bleeder screws and put the torch to it.
Left a dent in the wall but it worked.

Interesting idea. Didn’t you have to plug a passage to make this
work?

Any idea why it was so stuck? Rust inside? Was the piston stuck in
the seal or in the cylinder itself?

Anybody have any other good ideas for removing stuck pistons? The
problem generally is that there’s no good way to grab them. I
suppose that, if you’re going to replace the pistons anyway, you
could do something destructive.

Would it make good sense to try to push the pistons in first? That
only requires a pair of channellocks or a C-clamp or some such.
Might seem counterproductive, but if you get it to break loose it
should be easier to pull out.

Would it be a good idea to push REALLY hard on the brake pedal a
couple of times before beginning work? Or maybe, after removing
calipers and rotors, reconnect the brake lines and use the pedal to
get stuck pistons loose?

– Kirbert

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In reply to a message from Kirbert sent Mon 27 Mar 2006:

When I plan to remove piston, before removing anything, I take the
pads out, push the pedal a few times and that gets all the pistons
most of the way out. After that, I’ve not had a problem getting
them the rest of the way out with a bit of compressed air.–
Iain Burgess - 83 XJ-S Brisbane, Australia
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Iain_B wrote:

When I plan to remove piston, before removing anything, I take the
pads out, push the pedal a few times and that gets all the pistons
most of the way out. After that, I’ve not had a problem getting them
the rest of the way out with a bit of compressed air.

Then methinks you’ve never had a jammed piston. If you have a jammed
piston and you remove the pads and push on the pedal, the pistons
that move will happily come completely out of their cylinders and
dump brake fluid on the floor without ever budging the jammed piston.
You need to retain all pistons so they can move most of the way out
but not all the way. That way you can push HARD on the pedal, hard
enough to free the jammed piston.

I suspect the easiest way to limit the piston travel would be to
install a set of worn pads, worn down almost to the plates. I’m
pretty sure all these calipers are designed so that the pad can never
wear so much as to allow the piston to leave the cylinder.

Not having a worn set of pads on hand, perhaps the next best idea
would be to swap pads around. Presumably the pad against the jammed
piston has much less wear than the others because that piston hasn’t
been pushing that pad into service. So, swap that pad with a worn
one, pushing the free piston back to make room for the non-worn pad.
When you apply the brakes, the unworn pad with the free piston will
push against the rotor – but the jammed piston will be facing a worn
pad that’s nowhere near the rotor, so all the force will be trying to
free that piston.

I still think compressing the pistons back into the calipers would
probably be just as effective at freeing a jammed piston. The main
disadvantage would be that the pistons, being fully retracted, will
be more difficult to get a grip on to pull out.

– Kirbert

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In reply to a message from Kirbert sent Thu 30 Mar 2006:

Well, mine pressed up against the rotor when I did, and did
not dump fluid everywhere. Doubt if your rotors could be
worn that thin that the pistons would come out.–
Iain Burgess 83 XJ-S, Brisbane Australia
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Iain Burgess wrote:

Well, mine pressed up against the rotor when I did, and did
not dump fluid everywhere. Doubt if your rotors could be
worn that thin that the pistons would come out.

Hm. Maybe my Alzheimer’s is acting up again. My recollection is
that, when the pads were worn completely off and the backing plates
were rubbing up against the rotors, the pistons are right on the
verge of coming out of the seals. That would make sense to me, since
there’s no reason to make the calipers so much larger and deeper to
allow the pistons to move farther than that before coming out. But
perhaps they are, I’m thinking of something else.

– Kirbert

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