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The Jag-lovers Net Guide to Jaguars: Chapter 7

Chapter 7. The Jaguar XJ40 (1988-1994).

(Version 1 Rough Draft)

1. Overview of various XJ40 models.

The Jaguar XJ40 was the result of a 10 year design exercise with the Jaguar design department attempting to best the classic design of the first generation XJ6. The XJ40 prototypes began with a body design very similar to the final result, wandered through the boxy, angular shapes which were popular in the early-1980s, before returning to the body style that we know today as the XJ40.

While the XJ40 body design was simplified greatly over that of the series III XJ6, the XJ40 electrical system became much more complex.

If you interested in the new XJ40 model, then get a copy of the September 1994 Jaguar World magazine. They have an excellent 5 page article on buying a used XJ40. Currently, large numbers of early XJ40's are being dumped on the market at low prices due to many first owner leases ending. The jury is still out on the XJ40, but the picture which appears to be evolving is that, while early models had some some serious problems with their new electrical and mechanical systems, the later XJ40 models appear to be quite robust.

    "A business colleague and I bought our XJ40's from the same dealer, within a month of each other. This was two years ago. He has since sold his, because there was precious little that didn't go wrong with it during that time (Dropped valves, a new radiator, a new clutch fan, a gearbox, a rear end, dropped valves, instrument panels, Window motors? a radio, an aerial, 4 door handles, (same door??), new shock absorbers, air conditioning compressor, new brakes (discs) wheel bearings and power steering pump). Many more miscellaneous towings! All in less than 40,000 Kms.
    But mine just kept driving along. By comparison, I did 110,000 Kms in the same time and only had a fuel pump, new discs, and repairs necessitated when the thermostat seized and cooked the engine. Other than that one major repair (ouch) for a car of that mileage, I don't think it is too bad."
    Peter Rebbechi(
    "Likewise, I have now done 99,000 miles (160,000km's) and have had to repair or replace nothing other than the usual bushes, pads, shoes, shockers and not forgetting the tyres!!!! Tyres are the biggest overhead of all! I have had a few's amazing how sharp a hawthorn thorn is! No electrical problems (other than bulb out warning which I still live with). A little rust , mainly due to (Jaguar dealer ) repaired accident damaged front wing. Still on the original exhaust - minus the two mounting hooks above rear axle. I have of course spent a small fortune on Jaguar dealer servicing." Donald McGregor (

2. Specific problem areas with XJ40's.

The early 1988 XJ40 models were the least reliable, with electrical problems such as irratic guages, starter and fuel pump failures being very common.

The service record for 1989 models is also poor though the model year witnessed improvements such as new air vent designs that stayed in the dash when moved instead of falling out into your hands, improved switch assemblies for the cluster on both sides of the steering wheel column, and some improvements in the electrical harness.

Metric tires: Early XJ40's came with metric sized tires. The metric tires tend to be more expensive and come in fewer sizes than the more common standard sized tires.

The 1990-93 years were ideal years for reliability. Improvements were made to the power seat motors, improved sealing of the trunk (less leaks) and more improvements in the electrical system. Things to really look for are oil leaks at the right front corner of the head and rear suspension problems. The oil leak tends to be the head gasket and can be quite a problem. Look for oil between the distributor and the head. The rear suspension should be converted to standard to get rid of the hydraulics. After years of testing it has been found not to work properly.

    "A common problem with 3.6L AJ6 engines, is the intake manifold gasket leaking. The gasket separates and protrudes from the mating surfaces causing a vacuum leak and leaner mixture on the affected cylinder(s). When the engine is cold, it isn't usually noticed because the computer is creating a richer mixture. As the engine warms up to operating temperature, the mixture is leaned to the point that a vacuum leak can cause a rough idle." Loren Lingren
    "Wheel sensors are the single biggest failure in the ABS. And, just for the sport of it, a few diagnostic tips:
    1. The sensors get weak before they die totally. Causes intermintant "failures".
    2. Proper testing requires a lab scope, and a reference pattern/amplitude. however, you can do a rough-n-tumble by hooking a AC volt meter to the unpugged sensor. Compare side to side. At the speed *I* can spin the front wheels by hand, I want to see about 1 volt. At about 0.7v, the system gets upset.
    3. Ever notice how badly XJ40's chew up the brake rotors? Well as those filings from the rotors seem to gravitate (magnetate?) to the ABS sensors. Before replacing a suspect sensor, try cleaning all of the swarf from it and the reluctor wheel.
    The ABS does a two pass self test. First test is done directly at startup. When this passes, it will do the second part as soon as the car exceeds 5km/h. This second test is dynamic, firing off the pump and cycling all of the dump valves. This is what you are hearing. It is normal. It shouldn't be very loud."
    Randy Wilson

3. Prices of XJ6's:

As with any used car, there is no foolproof method for determining what the correct price of a used XJ40 should be. One metric is to see what similar cars are selling for in your local paper. An upper bound for the price can be usually be determined by looking at the prices being asked in the US publication "Hemmings Motor News". Vehicles advertised here tend to be in excellent shape and priced accordingly.

Recently (1995), the prices of XJ40 decreased greatly with the introduction of the new X300 Jaguar sedan. At the same time many XJ40 ownership leases ended and the cars were released to the market place. Lower bound prices for early model XJ40's currently appear to be around US$8000 and headed downward.


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