Jaguar XJ-S. Service manual — part 114

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Technically, the handbrake pads could be removed and reinstalled without taking the handbrake calipers out of the car.
Unfortunately, that won’t do any good, because to install new (thicker) pads you will need to readjust the self-adjuster
and install a new bronze fork. In other words, the handbrake calipers have to come out.

Do you really need a new bronze fork, or can you just rebend the old one? Well, if the handbrake pads are not being
replaced, you only need to spread the bronze fork a little bit prior to reinstalling, and you will probably get away with it.
If you’re replacing the handbrake pads, though, you will have to spread the bronze fork all the way back to its as-new
shape. Mike Morrin says, “Really bad idea. I have seen a couple of cases where the fork has broken due to metal
fatigue. In itself not a big problem, but both times the rotor was destroyed before the fault was noticed. Always replace
the forks when you have the hand brake calipers off. They are cheap.”

When you go to removing the pads from the handbrake calipers, the ROM, Section 70.40.04, says “remove nut and
spring washer securing pads to brake pad carriers, remove pads.” The Haynes says the same thing in Chapter 9,
Section 18, step 10. Removing that nut and spring washer is unnecessary; merely loosen it two full turns and the pad
will slide right out, leaving the bolt, nut and washer loosely in place. They even provided a little hole at the top center
of each pad to make it easier to grab and pull out. Of course, the new pads come with new screws in case you want to
replace them, but there’s really no need unless you strip them or something.

Just getting the nuts loose may be a challenge, though: The nut is 0.325” (8.25mm) across the flats. This isn’t even a
standard Whitworth size! Craig Sawyers says, “The nuts that secure the handbrake pads to the arms are 2BA. And
only a 2BA socket will get in there to remove the nuts.” Paul Burke says, “BA stands for British Association - believe
it or not. BA threads start at size 0 (zero) which is the biggest, and the bolts and nuts get smaller as the number gets
bigger.”

Well, at least you know what to look for. This author used an 11/32” socket which worked but didn’t fit too well; a
21/64” would have been better, if such a thing exists.

The bolt that this nut threads onto has an unusual head, but the threads are standard 10-28 fine thread. So once you get
those weird nuts off, you could put normal-sized nuts on to replace them -- but that might not work well, either. The
nut on the outboard side fits down into a well, and installing a nut with a larger 3/8” hex will probably mean you can’t
get a socket or wrench on it. This author found an excellent solution: the nuts used on military jet aircraft are extremely
high strength and high temperature, yet they are very tiny and require a 12-point box end wrench or socket to install. If
you can find a source for such nuts, they are highly recommended for this application. And you can leave the spring
washer out, since the military nuts are self-locking. You will need to find 12-point sockets or box-end wrenches in 1/4”
or 5/16” sizes; Snap-On makes them. I can guarantee they’ll be easier to find than 2BA -- at least here in the US.

The facing of the handbrake pads is a rectangular shape with a corner cut off diagonally. The end with the corner cut
off diagonally must go towards the rear of the car, or away from the pivots on the main caliper.

All agree on one important point: make very sure the fingers on the bronze fork are correctly in place in the little holes
when it’s all together. If one has slipped out, the handbrake pad will ride against the rotor, and this will damage the
rotor itself in only a few hundred miles.

HANDBRAKE CALIPER REBUILDING: Jan Wikström says, “The self-adjusting ratchet mechanisms in the pad
holders are quite likely to be clogged with semi-carbonized grease and dysfunctional; open the pad holders up, clean
out the ratchet mechanism and grease very lightly with high-temp grease or MoS

2

(molybdenum disulfide). Drowning

them in grease as the factory did is just silly; the ratchets may rotate one turn every few months and don’t really need
lubrication.”

Mack Kamna describes rebuilding the handbrake calipers on Jaguar inboard rear brakes: “In the past my parking brake
lever had to be pulled quite a ways to be effective. I found the self-adjusting nuts to be galled up with dry grease and
very tight on adjuster bolt threads. I cleaned them up and dressed the gear teeth with a small file, then greased both the
adjuster bolt threads (using C5A, anti seize), and the adjuster nut gear teeth (Hi-temp brake grease). I then installed the
handbrake mechanism assembly with new retraction plates, and adjusted the handbrake “system” per the manual.
When I pulled the handbrake lever, you could hear the adjusters smoothly clicking, and the pad assemblies tightened

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right up. I make no claims on my choice of lubricants; none of my 3 reference books on this maintenance task mention
lubrication, they have just worked well for me in the past.

“...With the lever released there is no drag on the rotors, yet it only takes three clicks to make the wheels unmoveable
by hand. I hope this can be of help to those of you who like myself have long suffered anemic handbrakes.”

This author went a different way with lubricants, and lubricated everything in the handbrake caliper self-adjusting
mechanism with graphite only. Graphite is good to extreme temperatures, won’t ever dry out (it’s dry already!), and
won’t collect dust and grit. The only concern is that it might not protect ferrous parts from rusting, and then the rusting
could cause the adjuster to seize up.

HANDBRAKE ADJUSTER LUBRICATION: It is possible to lubricate the adjuster too well. Peter Cohen: “Upon
refitting each handbrake assembly, it is an easy matter to operate the arm to check that the adjustment mechanism is
clicking, and, in fact, to adjust them up. The first one I fitted worked fine. The second one refused to click. I removed
the cover and refitted the mechanism to watch it in action. When the lever arm moves, it moves the piece of spring
steel that has a pawl that is supposed to catch the toothed wheel and drag the toothed wheel back a notch, if necessary.
What was happening on this one was that, when the spring steel moved, it was moving the toothed wheel in both
directions, accomplishing nothing. I couldn't figure out what is supposed to put drag on the toothed wheel to prevent
this from happening. Cleaning all lubricant off the threads wasn't sufficient. I finally applied a bit of dirt to the threads
to add more resistance, and now the adjuster works fine. I'm sure it is not what the designer had in mind, but it
worked.”

THE ULTIMATE SOLUTION TO HANDBRAKE PROBLEMS: Some so-called “Jaguar experts” actually
recommend removing the handbrake calipers from the inboard brakes entirely and throwing them away. This is
probably because they can’t figure out how to assemble them correctly. Obviously, it is irresponsible to recommend
that an automobile owner simply remove a piece of safety equipment, but it is interesting to note that the handbrake
calipers can be removed without adversely affecting the operation of the foot brake. The Jaguar is a rare example of a
car on which this is possible.

SCRAPE, SCRAPE, SCRAPE: Ron Ickse describes the cause of a scrape, scrape, scrape sound that seems more
pronounced when turning one direction and goes away when turning the other direction: “I've had this now three times
on Jaguars over 20 years. In each case, it turned out that the retracting spring on the handbrake mechanism on one side
or the other had failed, allowing the handbrake pad to remain in contact with the disk. Eventually, the pad wears down
to the metal, so then you hear metal-to-metal contact. If the disk isn't quite true, you'll get the characteristic intermittent
scraping noise. Fiddly but not particularly expensive to mend, if you (or your mechanic) knows what's what with
Jaguar brakes.”

TWR Rear Brakes

The rear brakes on a TWR are essentially the same idea as the do-it-yourself mod described starting on page 440; in
fact, the www site listed includes a page of pictures of the rear brakes on Alan Heartfield’s TWR.

If you own a TWR and need new rear rotors, Heartfield found a company that’ll provide special-order outer discs for
reasonable prices:

Essex Parts Services Inc.
2350 Industrial Park Blvd
Cumming, GA 30041-6460 (US)
770-889-4096
fax: 800-335-7223 or 770-889-5256

http://www.latemodel.com/essex/

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Heartfield used Essex just to get replacement disks for his TWR since it proved easier and cheaper than trying to find
genuine TWR parts. There are other companies that can provide such discs, including Wilwood.

Ordering discs through Essex involves filling out a “Custom Brake Disc Order Form” which they can fax to you. In the
middle of the form there is a chart where you must fill in “Nominal Dimensions” of the discs you need. Fill the form in
as follows:

MOUNTING HOLES

ØA

OUTSIDE

DIAMETER

B

THICKNESS

ØC

EYE

DIAMETER

ØD

FLANGE

INSIDE

DIAMETER

E

OFFSET

NO. DIAMETER ØM

PCD

APPROX.

WEIGHT

10-3/8” 0.78” 6-3/4” 4.90” 0.39” 6

1/4” 5.50”

The rest of the form is self-explanatory -- name, address, credit card number, etc. You can opt for tricky stuff like cross
drilling or face grooves if you want. Essex will quote you a price once they get the form.

Note: the design shown starting on page 440 is not exactly the same as that used in the TWR, so don’t use the Essex
order form shown there for getting replacement discs for your TWR.

Heartfield’s TWR happens to have a Dana final drive unit. With the TWR vented rear brake design, it appears that the
calipers were offset inboard by about 1/8”. This may have been accomplished by milling 1/8” off the calipers
themselves or off the mounting bosses on the Dana final drive unit. If you need to replace either the calipers or the final
drive unit on a TWR, you should check these parts carefully to see if the replacements will need to be modified
accordingly. If the Dana final drive is replaced with a Salisbury (the standard repair procedure) it would appear that
1/8” spacers would be required between the calipers and the output shaft mount flanges -- spacers that would probably
be lots of fun installing. If you run into stuff like this, you might opt to rebuild the calipers or final drive unit rather
than replace them -- or you might opt to machine a 1/8” step in the inner hubs of your rotors like the ones shown on
page 443, since the purpose of that step is to provide an assembly that doesn’t require offsetting the calipers.

Outboard Rear Brakes

Chad Bolles says the outboard brakes used on the later XJS are exactly the same as those used on the XJ40. Stephen
Gibson says, “Outboard brakes on the XJS started at VIN 188105 with the solid rear disc for the 4.0 and 6.0 litre. The
vented rear discs came in at VIN 198335.”

Handbrake/Parking Brake/Emergency Brake/Whatever

The handbrake used with the outboard brakes on the later XJS is actually a drum brake within the center portion of the
disk rotor. Stephen Gibson says, “The outboard handbrake mechanism and shoes are identical for the XJ40 and XJS
installation. When the vented rear discs came in the same handbrake mechanism and shoes were retained. They
naturally have the same part numbers.”

HANDBRAKE LEVER JAMMING: This has only been reported on the cars with outboard rear brakes. The
handbrake will not release, no matter what. Gary Penovich says, “One thing to try before you go through all this is to
make sure the hand grip is back as far as it will go on the lever, before pushing the button. It has a habit of moving

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forward, and blocking one's thumb from pushing the button in far enough to release the brake.” Of course, you might
just opt to take the grip off and throw it away.

The problem probably isn’t the grip, though. “It can be fixed. But, unfortunately, to really get good access to the lever
assembly, you need to remove the four bolts holding the drivers seat to the floor, and tilting the seat up and away from
the lever.

“Once you have good access to the lever assembly, remove the plastic cover. I believe it is held on with only one
screw. Once off, you will see that the lever terminates at a flat, round metal plate. In the inner area of this plate is a
slot. In the slot is a relatively thin, curved, metal rod. That rod is supposed to move with the lever/plate, when you
press the thumb button and move the lever. Unfortunately, it appears that the lever can be over-tightened, causing the
rod not to be able to engage properly in the slot.

“Take a large, flat-head screwdriver, and jam it into the slot, so that when you move the lever, the rod will move with it.
That will force the rod to disengage the brake. Once disengaged, spray some WD-40 around the whole mechanism,
and up inside the underside of the lever in the channel where the rod travels. Also, check the mechanism a number of
times before putting the cover and seat back.”

Brian Jamieson had the same problem: “I was able to remove the cover on the handbrake lever without removing the
seat.” He used a Pozidriv tip for an interchangeable-tip screwdriver. “It is only one inch long and with the seat moved
forward and the back tilted forward I could get this on the screw and turn it with a small quarter inch wrench. When I
got the cover off I pushed/levered the small rod that is connected to the button and then pushed down on the handbrake
cable which dropped down and released. I think the cable was binding where it goes into the outer cover. Anyway,
problem solved for the time being.”

ABS Brakes

Antilock Braking System (ABS) brakes have gotten a lot of press. Essentially, the system involves sensors in the
wheels that sense when a wheel has stopped turning and releases the brake on that wheel. When the wheel resumes
turning, the brake is reapplied. If the brakes are applied forcefully enough, this results in a “pulsing” as the brakes to
each wheel are cyclically applied and released.

When initially developed, ABS was expected to provide a considerable safety benefit; in fact, many auto manufacturers
pursued development of ABS in expectation that it would later be required on US cars. After a few years of voluntary
application (typically on higher-end cars such as the XJ-S), accident statistics failed to confirm any safety benefit, so
proposals to require ABS have been stifled.

In a straight line on dry pavement, ABS brakes do little good; a car with comparable conventional brakes can stop in
essentially the same distance. However, the application is different; on the car with conventional brakes, the driver can
achieve the best stopping distance by applying the brakes as hard as possible without locking the wheels, and many
skilled drivers are very adept at doing so. On the car with ABS brakes, the driver might as well simply jam the pedal as
hard as possible and let the ABS work. While this was originally expected to be one of the safety benefits -- the driver
no longer needs to be skilled at braking -- it is theorized that this is in fact one of the reasons the statistics haven’t
panned out; the driver is still trying to modulate the brakes carefully as before, and he and the ABS system don’t work
together well and result in longer stopping distances.

In a straight line on wet pavement, ABS has little benefit as well. Since the car does not stop as quickly, there is less
weight shift from rear to front, and a set of conventional brakes with fixed proportions between rear and front may lock
the front wheels. However, the vast majority of conventional braking systems had addressed this problem decades ago,
providing more rear braking at light pedal pressures with the emphasis shifting forward as the pressure increased.
Perhaps the biggest benefit of ABS here is control, since a car with the wheels locked may turn sideways on slick
pavement.