Experience in a Book
Brake System

BRAKE BLEEDING: Bleeding the brakes is essential after disconnecting brake lines in order to get air out of the system and ensure a "hard" pedal. Bleeding is also a periodic maintenance action, sorta like changing the oil; brake fluid absorbs moisture, either that was already within the system or from the air in the reservoir, and this moisture is not good for the insides of the brake cylinders. Also, the fluid eventually becomes contaminated with tiny particles of metal from wear within the cylinders, and the particles only serve to accelerate the wear. So it is beneficial to occasionally bleed the brakes even if there is no air in them, and to bleed them enough that the entire system is filled with fresh fluid.

Bleeding the old-fashioned way requires two people. One person sits in the car and "pumps" the pedal to get the pedal up where it belongs, and then holds pressure on the system while the other person opens one of the bleed screws to allow the fluid to squirt out. A small piece of hose routed into a container helps reduce the mess. When the bleed screw is opened, the pedal will go to the floor, and the person in the car must keep it there until the bleed screw is closed once again; if the pedal is allowed to rise, it will draw air back in through the bleed screw. After the bleed screw is closed, the pedal is pumped back up and the cycle is repeated. If a clear hose is used on the bleed screw, it is easy to see when the crud is gone and clear fluid is coming through. You must pause every now and then to top up the reservoir with fresh fluid.

If you want to make things easier or require only one person, there are numerous gadgets available to help. Dan Welchman suggests the "Eazi-bleed" kit: "I think they're made by Gunsons but I'm not sure. This device uses your spare tyre as a compressed air reservoir which pressurizes a large plastic brake fluid reservoir via a hose and footpump-style valve connector. A tube dips into the bottom of this reservoir and feeds fluid up to an air-tight cap that screws onto your brake fluid reservoir on the car (the kit comes with a wide range of different caps and rubber gaskets to fit most cars).

"Once you've fitted this and got it air-tight you can bleed the brakes by just opening each of the nipples and letting the fluid flow out until it's bubble free (or longer if you're changing the fluid). No pumping, no assistant needed, and no worrying about having to top up the reservoir for fear of running out of fluid and pumping air through the system. They're extremely cheap and work pretty well."

Brian Schreurs reports: "I shall quote directly: "One of the hottest new items at the SEMA [Specialty Equipment Manufacturers Association] show (winning the ëBest Engineered New Product' category) was Russell Performance Products' Speed Bleeder brake bleeder screw. This unique product replaces the stock bleeder screw on your car, truck, or motorcycle. It has a patented, internal, spring-loaded check ball that permits air and fluid to escape when the pedal is depressed, but automatically seals when the pedal is released." Of course they can be capped off so that pressure is not lost when the brakes are not being bled. They are supposedly available nationwide, but if all else fails the company can be contacted directly at

225 Fentress Blvd
Daytona Beach, FL 32114
+1 (904) 253-8980

Ed. note: Speed Bleeders are offered by Griot's Garage.

BRAKE FLUID RESERVOIR CONNECTION HOSE: To make the brake fluid reservoir fit under the hood, Jaguar uses a remote reservoir connected with metal lines and short pieces of flexible hose. If these hoses need replacing, do not use conventional fuel line; the brake fluid attacks the fuel line material, and the result will be darkened fluid with lots of crud in it.

The fact is, none of the hose commonly sold at an auto parts store will serve. Also, nylon tubing is unsuitable; the brake fluid soaks right through it, and then it hardens and shrinks.

Of course, using Jaguar original hose is not recommended, as it is a British non-metallic product. After all, you are now having to replace it. But there are other cars that also use hose to connect a remote reservoir to the master cylinder, including Mercedes, BMW and Fiat, so you can check other dealers for suitable hose. Andrew Weinberg says, "Volkswagen Beetles also use a remote reservoir, and the hose stocked for that application works perfectly... The hose is available from any VW supply shop. The only hitch is it's a (nice?) blue color."

Non-automotive hose is also a possibility. You can visit an industrial supply store and attempt to find a clerk who knows his stuff, or a reference manual that lists acceptable applications for different hose materials. Commercially available air hose works well in this application; it is red with a black inner liner, and is sold in many hardware stores. It's so cheap that many Jaguar owners can't believe it could ever work.

Keep in mind that this application sees no pressure, so high-pressure brake or hydraulic hose is unnecessary and will only make it very difficult to install over the plastic fittings.

BRAKE FLUID LEVEL SWITCH: Hey, it's electrical, so it's in the section on the Electrical System.

BRAKE FLUID RESERVOIR CAP FAILURES: Apparently the cap occasionally breaks into a center portion and an outer portion. According to Michael Neal, "This is a problem and tends to reoccur if you don't modify the reservoir. This is on the pre-abs XJ-S brake reservoirs. Usually just flattening the sharp vertical ridge on the reservoir with a file will do it."

MASTER CYLINDER REBUILDING: There was an "early" type master cylinder used before 1977‡, and a "later" type used up until the advent of ABS brakes. However, apparently not all of those "later" types were the same. In the Jaguar manual section 70.30.09, step 14, a seal is installed on the secondary piston with the lip facing forward. In step 15, a second seal is installed in a second groove facing rearward. Chapter 9, section 7, steps 13 and 14 in the Haynes manual say essentially the same thing. However, some master cylinders only have one seal on the rear end of the secondary piston rather than two. The one in the first step is the one that was omitted; if only a single seal groove is available, the lip on the seal should be installed facing rearwards. Of course, if you have purchased overhaul kit #M7673, you will have one seal left over.

DOT 5 BRAKE FLUID: Many people swear by "Dot 5" silicone-based brake fluid, and others swear at it. Silicone brake fluid does not absorb moisture, does not harm paint when spilled, and has a very high boiling point. It is also non-toxic.

Some of the arguments are based on it not absorbing moisture. If there is no water in your brake system to begin with, theoretically none will get in by being absorbed by the fluid in the reservoir. But if there is water in the system to begin with, the silicone fluid will not absorb it, and it may puddle in local spots and cause corrosion.

Silicon fluid absorbs more air than conventional fluid, meaning that the brake pedal will feel spongier, even when fully bled. Of course, this will not be apparent at first, since it takes some time to absorb air within the reservoir and for the air to diffuse throughout the system.

It is reportedly of some importance that the two types of fluid not be mixed. Silicon fluid is less dense than normal fluid and won't mix with it, so it is theoretically feasible to fill the reservoir with silicon fluid while bleeding the conventional fluid out at the wheels.

There is even some misunderstanding about the name. DOT 3 and DOT 4 brake fluids are referred to as such because they conform to Department Of Transportation standards. "Dot 5" silicon-based fluid, however, is a trade name, not a DOT standard. There are even reports that DOT has now issued a standard #5, and it is not for silicone-based fluid but for something else.

There are also reports that older Girling systems require DOT 4 fluid to keep the seals pliable to seal properly. Some components are reported to get hard when exposed to silicone fluid; others are reported to absorb too much silicone and swell so much as to jam the works.

According to Jim Beckmeyer, who had a master cylinder resleeved: "White Post said that the warranty would be voided if I used DOT 5". Draw your own conclusions.

One thing is apparent to all experts: If your car is using DOT 3 or DOT 4 brake fluid, it should be flushed according to the maintenance schedule. If left in too long, the absorbed water will cause corrosion throughout the system.

POWER BRAKE SERVO: The (non-ABS) servo assembly comes apart in the center, by twisting one half until the retaining tangs line up with the cutouts. There is a special tool for this job, but Bruce Hayes reports the tool can be improvised. He carefully mounted the master cylinder in a vice, and fashioned a tool to attach to the studs on the housing to turn it.

FRONT BRAKE ROTOR REPLACEMENT: Jaguar chose to bolt the rotor to the inside of the hub flange, rather than the outside like intelligently-designed cars. As a result, the hub must be removed to get the rotor off.

The various manuals suggest unbolting the rotor from the hub during this process by inserting a tool through the opening in the dust shield. However, Nance O'Neil points out that there is no need to unbolt the rotor before removal, and instead the hub/rotor assembly can be removed as a unit and then disassembled on the bench. Either way, the brake caliper must be unbolted.

John Himes adds a tip: "The 5 bolts that hold the rotor to the hub assembly can be very stubborn, especially when working alone. If you place the wheel face down, then place the lug nuts through the holes, now you've got a nice big vice to hold it in place without buggering up anything."

Matthias Fouquet-Lapar has an alternative suggestion: "I actually took the hub out and put the disk in a large bench vice. When I mounted the new disk, I simply used the old brake pads to protect the disk from the vice."

REAR BRAKE PAD CHANGE: The CATALOGUE passed on this tip from the Jaguar Club of Pittsburgh. To get the old pads out, tie a piece of wire to them connected to a turnbuckle tied to the transmission mount. Tighten the turnbuckle while tapping the pad with a hammer to remove the pad.

REAR BRAKE ROTORS: According to Michael Neal, the rear brake rotors on the XJ-S are a "sandwich" construction: "The stock rear rotors have the actual thin outer rotor surface attached to a solid core. These thin outer surfaces are very brittle and break easily."

If problems occur, Neal recommends the use of aftermarket solid disks. Apparently, when you order disks from some suppliers like Special Interest Car Parts, they will send you the solid rotors rather than even asking; the aftermarket parts are what they stock.

"With the amount of work that is involved in getting the rear calipers out I think that I would replace the rear rotors while I was in there. Never turn the rear rotors, the oem style rotors are sandwiched construction and would probably self destruct when you put a bit to them. The aftermarket style could probably take one light surfacing but it just isn't worth it, price them sometime, they aren't that much."

Randy K. Wilson concurs: "Don't bother turning the rear rotors. It's around eight hours of labor to get the things out. If they are bad enough to require turning, the labor involved warrants replacing them with new ones. Besides, it's rare for those rotors to be torn up and still be turned down and remain in spec."

Of course, you might consider aftermarket ventilated disks, too.

REAR BRAKE DISASSEMBLY: John Himes found out that both the Haynes manual and the Jaguar manual described incorrect procedures for this job, at least on his '88. "They are wrong on how the calipers mount. Both manuals tell you to break the wire and remove the bolts that are shown on the outside of the calipers. There is no wire & the bolts are on the inside of the calipers. You must move the wheel to align a hole in the rotor to remove/replace these 2 bolts."

Randy Wilson says this problem is caused by the difference between the Salisbury and Dana differential units.

BRAKE CALIPER OVERHAUL: Before removal, see the comments regarding the steering arm shims in the section on Suspension/Steering.

On the rear calipers, brake fluid communicates from one side of the caliper to the other via a "bridge pipe", a short piece of brake line that connects to each side with threaded fittings. The front calipers, however, have no such pipe; fluid communicates between the two sides via a drilled passage through the caliper halves themselves. Hence, there must be a seal between the two halves to prevent leakage.

The official Jaguar repair manual starts: "CAUTION: Under no circumstances must the caliper halves be separated." Apparently good advice; the seal between the halves is difficult to find, and the caliper overhaul kit does not include it.

So; you took the calipers apart and then checked this manual! Shame on you. According to Rob Reilly, you can get the seals from John Farrell (see page *). Other possibilities include a Chevy dealer.

BRAKE CALIPER RESTORATION: Old brake calipers are often restored to usable condition by the fitting of brass or stainless steel sleeves. Thomas L. Felts sends his experience: "I had all of my brake cylinders rebuilt several years ago...they were rebuilt using a brass sleeve, which, three out of the four wheels had the sleeves separate. Two earlier on. I have had a number of people tell me to never use brass as a sleeve."

BEDDING IN NEW/REBUILT BRAKES: The frequency of this complaint, on Jaguars as well as other cars, indicates that the following advice should be followed closely. Allan Charlton explains: "My son works in a car parts firm, and they have had disk pad bedding-in problems. It seems that the new asbestos-free pads need to be bedded-in properly or they can cause damage. In their experience (mostly VW Golf, but also BMW and M-B) disks were blued and warped, but the following procedure has eliminated the problem entirely.

"Accelerate to 60 km/h. Use moderate brake pedal pressure to slow to 5 km/h. Do not stop the vehicle, but accelerate to 60 km/h again. Repeat ten times, with about 500 metres between applications, then stop and let the brakes cool.

"Use the brakes moderately for the next 300 km, and do not get them hot. After that, they should be OK. The procedure is intended to be used when you first install the disks--it won't repair damage already done."

Peter Cohen adds, "Jaguar actually includes a paper with approximately these instructions in the box with their brake pads."

BRAKE SQUEAL: Dean Gosselin sends this tip: "I have traced a major source of brake squeal on my 1991 XJ-S to a tire clean/shine product called "Formula 2000". After 4-6 weeks of not using this product the brake squeal is nearly gone. I traced this cause to the spray-on tire cleaning product after my father used the stuff on his Audi and it immediately resulted in major squeal under braking."

DIRTY FRONT WHEELS: Dust from the front brakes tends to get the wheels dirty, especially if you use them hard. There is a device available to prevent this problem. It's called Kleenwheels, and it's essentially a disk that seals the wheel on the inside so the dust can't come out through the openings. They are available at many auto parts stores. Ed Avis reports that the no-name "turbo-vented dust shields" sold by J. C. Whitney, catalog number 78xx6976BF, are in fact genuine Kleen Wheels. He also provides the info on the company itself:

Kleen Wheels
5000 Oakes Road, Suite H
Ft. Lauderdale, FL 33314
+1 (954) 791-9112

It would be logical to assume that cutting off this airflow path would result in a reduction in brake cooling, and therefore poorer braking performance under severe, repeated braking. However, most users don't notice any detriment (perhaps because they never use their brakes hard enough for overheating to be a problem). The primary cooling airflow is from the inboard side of the brakes to the inside of the hub and outward through the ventilated disk. The warmed air can then go either out through the wheel or inward under the car. The use of Kleenwheels prevents the first exit, so all the air goes inward. So, the use of Kleenwheels won't reduce the airflow to the brakes, but it may cause more of the warmed air to recirculate back through the brake again. Considering the airflow underneath the car during any activity where hot brakes are a concern, this is probably insignificant.

Handbrake / Parking Brake / Emergency Brake / Whatever

CABLE ADJUSTING: In short, don't. The cable adjuster is right behind the lever under the carpet on the XJ-S (different location on the XJ12, which has a pull handle under the dash), but is not intended to need adjusting as the pads wear. The emergency brake mechanism at the rear end has a self-adjusting feature and should maintain proper operation of the handbrake throughout the life of the handbrake pads. If the handbrake seems to need adjustment, either the self-adjuster has failed or seized, the pads have reached their wear limit -- or you have the wrong idea of what this handbrake should feel like.

The cable adjusting procedure described in the repair manual stipulates that the handbrake lever should be released and the cable adjusted so there is some detectable slack. That means that the two levers on the brake assembly itself should be fully released and applying no tension to the cable. This is necessary to allow the self-adjusters to work. If the cable is adjusted too tightly and the brake levers are not released fully, the self-adjusters may never work and the pads may drag, so you will be adjusting the cable again soon.

If the cable is adjusted properly, it should not require loosening in order to disengage or reengage the cable at the levers on the brake. It should be possible to pull the levers together enough to pop the cable off or to pop it back on. Note that it will require moving both levers, however; one is operated by the cable itself and the other by the housing moving the opposite direction, but both movements will be needed to disengage the cable.

EMERGENCY BRAKE REBUILDIING: Mack Kamna suggests the following procedure; he wrote it for the inboard brakes, but will probably apply to any emergency 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 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."

EMERGENCY BRAKE PAD CHANGE: Yes, the emergency brakes use dedicated pads on the XJ-S. Jan Wikström: "It's a fairly tinkery job, and definitely easier the second time... If you have a reasonable manual with a good picture of the system, patience is really all you need (you'll be working by feel as you can't see the upper side of the handbrake bits). A point: the bronze fork that positions the handbrake pads off the disk will be bent in if the pads are seriously worn and will need to be opened out to fit the new pads. Just tinker until it slips in easily.

"Another point: 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 MoS₂ (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."

ABS Brakes

Antilock Braking System (ABS) brakes have gotten a lot of press. Essentially, the system involves sensors in the wheels that sense when the 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 is 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 both he and the ABS don't work together as 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.

In a straight line with water or oil only on one side of the car, ABS offers a major benefit. If the conventional brakes are applied hard, one side of the car will slide and the car will turn violently. Alternatively, if the brakes are not applied that hard, it takes a long distance to stop. ABS allows the brakes on the dry side to be applied hard while the brakes on the wet side are kept from sliding, and the car can be brought to a rapid halt in controlled fashion.

In a curve, ABS provides perhaps its greatest benefit. If conventional brakes are locked in a curve, the car will slide in a straight line, which runs it off the side of the curve and into a tree or over a cliff. Skilled drivers know this and never apply the brakes hard in a curve; they will aim the car straight, even if it's aimed off the road, before applying the brakes hard. With ABS, however, it is perfectly workable to apply the brakes hard in a curve, since the wheels won't lock and control will be maintained. Since the curve causes a weight shift to the outside, the outside brakes can be applied forcefully without locking the lightly-loaded inside wheels. However, this is yet another possible reason that ABS hasn't lived up to its promise of increased safety; drivers may still refuse to apply the brakes hard in a curve.

Loose-packed snow, gravel, or the like, may be one of ABS's most notorious shortcomings. On such surfaces, the quickest way to stop a car is often to lock up the wheels and let them dig in. However, ABS prevents this from happening, so the car seemed to roll along forever, pulsing all the way. If the car in front doesn't have ABS and has dug its wheels in and stopped in short order, this can be a real problem.

Of course, stunt drivers don't care for ABS. When you see those guys in the movies spin the car around backwards and take off in the other direction, rest assured they do not have ABS; that 180† spin requires that the steering wheel be turned first one way, then the other way hard and the brakes locked. With ABS, they'd probably just drive off the side of the road.

ABS brakes were introduced on the XJ-S in mid-1989.

BLEEDING: Randy Wilson says "The brake pedal will sink fairly slowly when bleeding brakes. This is due to the fluid having to wander through the maze of valves and such that make up the ABS control block. Bleeding the brakes is a normal procedure like most any other car. It just requires a bit of patience. Do not jam on the pedal to force the fluid out quickly. Just let it go at its normal flow."

ALWAYS USE DOT 4 FLUID: Greg Meboe clarifies: "ABS systems call for (and need) DOT 4 fluid. Not DOT 3, not "DOT 5" (silicone). This is not the same thing as the early British systems. The fluid required in the 50/60's cars must be compatable with the rubber used. The fluid readily available in the US for this just so happens to be DOT 4 spec. ABS systems require the boiling point (wet) of DOT 4 fluid, and don't care about being compatable with old British rubber.

Reportedly, Pat Goss, the host of the TV show Motor Week, said the following: "Never use silicon brake fluid in an ABS system! [Silicon] brake fluid doesn't like the pumping action of the ABS pump. The pistons move so rapidly that it causes the silicon to foam and all of a sudden you have aerated fluid and you have a pedal that's on the floor."

PAD CHANGE: If the car has ABS brakes and the calipers are pressed back, fluid within the calipers is forced back up the lines and into the master control system. Since the fluid that has been within the calipers for some time often has a high degree of contamination (wear particles from the cylinder walls, etc.), when this fluid is backed into the controls it tends to cause problems. It is suggested that when pressing the calipers back (like when installing new pads) to open the bleed port and allow the fluid to drain rather than pushing it back up the lines.

Perhaps this isn't a bad idea with any brakes.

TESTING: Michael Neal writes: "I do extreme situation ABS test on cars during major services. I get quite a few surprises. Even from a moderate speed of 45 mph I've had cars yank the steering wheel out of my hands and the car ends up rotating 30 or 40 degrees. This is usually caused by a sticking piston or slide on a caliper."

Pat Goss, the host of the TV show Motor Week, reportedly advised to "exercise" the ABS at least once a month on a gravel road or in a wet parking lot. (Meaning, jam the brakes and let the ABS kick in.)

WHEEL BEARING FLOAT: LaRue Boyce says, "If you have trouble with the ABS unit, check out the front wheel bearing float; it will cause the sensor to report brake problems when it is working fine."

On to the Suspension & Steering