Here are some quick remarks on some of the more common repair issues and questions. Most of these items pertain to the Series I-II-III XJ Saloons but you XJ-S owners may find some useful tips, too.
Wipers don't self-park
The fault here almost always lies with the column mounted control switch and not with the "park switch" on the wiper motor. (Ser III)
Clunk, rattle, crunch noise over bumps
The upper bushings for the front shocks are almost always disintegrated on these cars, allowing the shock to rattle against the inner fenderwell. New replacement bushings are available separately and many owners have successfully used generic bushings from a local parts supply. Also check the braces which run diagonally from the cowl to the fenders (wings). Make sure they are tight......very tight. Anything thing less will allow them to makes noise as the body flexes.
Power door locks inoperative or slow working
In about 80% of the cases the recalcitrant locks can be brought back to life by removing the door trims and thoroughly lubricating all the linkages and sliding points. Use an aerosol lubricant, silicone spray works well. (Ser II and III)
Vibration felt when brakes applied
This is usually caused by warped brake rotors. Rotors can often be taken to a machine shop and be resurfaced but most owners replace them with new ones. The new ones are not too expensive and, since the job is labor-intensive, it makes sense to just install new ones.
Speedometer inoperative or erratic
In about mid-1982 or so (for North American market cars, later for rest-of-world) Jaguar switched from a cable-operated instrument to an electric one. A transmission-mounted transducer produces a signal which is sent to the speedometer. This transducer is the most common culprit when you speedo acts up or just plain quits. Of course the connections should be checked first. (SerIII)
Cruise control does not work
There are many possibilities here but often the fix is easy. First, check the 2-amp fuse (#12 fuse, main fuse box). Next check the vacuum bellows. This often leaks at the edges and can be cleaned and resealed with silicone sealer. Don¹t forget to check the vacuum supply to the bellows. The hose may have perished with age. (SeriesIII)
Engine will not crank
Assuming the battery is good, here are a couple of quick checks. Examine the battery cables/terminals for cleanliness and tightness. Ditto for the two firewall-mounted junction posts. Also try tapping the starter relay (firewall mounted, silver, oblong). If tapping the relay brings the starter back to life then replace the relay or disassemble it and clean the contacts.
Power antenna won¹t retract all the way
Examine the mast for slight bends and gently reshape by hand, if needed. Thoroughly clean the mast and lubricate it with an aerosol lube (silicone, graphite, etc). In nearly all cases this is all that's required. (Series II and III)
What is normal engine temperature?
Normal operating temperature is 88C-90C degrees. This is the beginning of the green band on the temperature gauge (SeriesIII 6-cylindercars). If the cooling system is in good order you should have no problem staying at the 88C-90C range unless you are in extreme conditions, i.e.: bumper-to-bumper traffic and/or ambient temps of 90-100F degrees. The auxiliary electric fan will come on at about 95C degrees. In high ambient temps I would say that anything over 100C degrees is cause for concern. In cooler temps, anything over 90C merits investigation.
Identification of sensors on the water rail
On the fuel injected 6-cylinder cars, here's what the different sensors are and what they do, starting from the front position. First is the Thermotime Switch. This is a heated switch. It controls the cold start injector. This switch operates only when the starter is engaged and only when the engine is cold. Next is the sending unit for the dashboard mounted temperature gauge. Next is the fuel injection coolant temp sensor, which sends a signal to the boot-mounted ECU (Electronic Control Unit). This sensor is an important part of the fuel metering system. Rearmost is the temperature switch for the air injection pump and the canister purge system. On some non-North American and/or SeriesII cars this sender is replaced by a vacuum switch for the EGR-equipped cars.
Identification of firewall relays
On 6-cylinder fuel injected cars, starting from the right (viewed from driver's seat) you have: The all-red Diode Pack. This is not actually a relay. It has several diodes inside and directs the flow of voltage in the fuel pump circuit. Next is the fuel pump relay. Next is the "main" relay, which feeds the injector ballast and a portion of the fuel pump circuit. Furthest inboard is the silver starter relay. Note: The location of the fuel pump and main relays can be inadvertently reversed. The fuel pump relay is easily identified by the white/green wires, which are not there on the main relay. Incidentally, the 6-cylinder cars do not have a "cold start" relay. The repair manual is confusing in this regard. The SeriesII XJ6's with fuel injection have a large, single, combination relay in place of the diode pack, main relay, and fuel relay. This combination relay was also used on a few of the very earliest SeriesIII cars.
Power windows inoperative
In a great many instances the cause is dirty contacts inside the window switches. On SerII and III cars (perhaps Series I, too. Not sure...) the switches can be easily accesses by removing the console cubby box and releasing the switches from the rear by depressing the retaining tabs. The switches can be removed, then, from the front. Do one at a time to avoid mixing up the wiring. A good aerosol contact cleaner (i.e., from Radio Shack) can be squirted into the switches through the small holes in the sides. Or, many owners have reported that the switches are relatively easy to disassemble and the contacts can then be easily cleaned with a pencil eraser.
Tires
Hours could be spent on the very subjective topic of tires. All owners agree that a high quality tire is called for. Jaguar specifies a "V-rated" tire for the XJ sedans and the many owners insist that this recommendation be adhered to. The V-rated tires, generally speaking, have stronger casings and sidewalls. It must be stated, however, that many owners have been perfectly happy with more ordinary S-T- or H-rated tires. The Series I and II cars used a 205/70x15 or ER70x15. The early SeriesIII cars also used a 205/70x15. However, about mid-way through the SeriesIII production a 215/70x15 became standard issue on North American spec cars. All V12 SeriesIII's used the 215/70 tire.
Interior lights inoperative from door switches
A few shots with your aerosol electrical contact cleaner will almost always bring recalcitrant door jamb switches back to life.
Erratic headlamp operation
In most cases the fuses (in under-bonnet fuse box ) are dirty, loose, or corroded. Easy fix. Replace the fuses or at least clean the end caps. Gently clean the fuse clips and, if the fuse is a loose fit, carefully bend the clips to restore a snug fit.
Wheel alignment
Front wheel alignment on a XJ sedan is no more difficult than any other "ordinary" car, and, in fact, is easier than many. Jaguar specified that special links be used to compress the suspension to simulate a laden condition. Since our Jags are seldom driven fully laden, this step is not necessarily needed. The Jaguar adjustment shims are a bit unique but just about any alignment specialist will have something suitable as a replacement. Alignment of the rear wheels is limited to the camber adjustment only. It is a labor-intensive job and seldom required.
Automatic transmission fluid
Looked in your manuals and wondering what "Type G" fluid is? You're not alone. It is an obsolete designation. If you have a Borg-Warner transmission (all 6-cylinder cars, V12's up to about 1978 or so) the correct replacement is "TypeF" or "Type FA", both readily available. Some owners use Dexron and report a softer shift with no problems.( If you have a 12 cylinder car with the General Motors TH400 transmission the correct fluid is Dexron and only Dexron.)
Electrical gremlins
The horror stories are highly exaggerated. In many cases the problem is not a faulty component but, instead, a faulty fuse and/or dirty, loose connectors. If your Jag develops an electrical glitch, always start by checking fuses and connectors. Always ! Don't assume a fuse is good just because it looks OK. Test it or replace it to be sure.
Shock absorbers
Shocks are available from Koni, Monroe, Bilstein, KYB, Woodhead, etc. However, the vast majority of owners seem to prefer and recommend the Boge brand. Boge was the OEM supplier for many years.
Cold water slosh on turns
When using your air conditioner it is normal for condensation to develop. The evaporator case has drains to let the condensate escape. These drains often clog and the result is cold, brackish water pooling in the case. It sloshes out on turns. With the car safely elevated the drains can be cleared by probing them with a piece of stiff wire. The two drain tubes can been seen existed the floorboards on either side of the transmission tunnel, just aft of where the engine and transmission come together.