Why aren’t the Jaguar XJ6 and XJ12 worth more?

XJ6 Series I front 3/4

The XJ6 sedan was the last Jaguar designed by company founder William Lyons, and it was so good that while other sedans bit the dust, the car would stay in production for more than two decades. Introduced in late 1968, it combined refinement, luxury, 120-mph performance, and superb handling.

1969-87 Jaguar XJ6

The signature 4.2-liter DOHC six-cylinder delivered 180 horsepower, along with four-wheel independent suspension, power rack-and-pinion steering, power disc brakes all round, and an automatic transmission. The cars featured leather seats, walnut fascia, and sufficient gauges for a small plane. An estimated 254,512 XJ6s were sold in 18 years.

Today, with the exception of low-mile originals and limited-production coupes, XJ6 prices linger in the used car basement, in the $3000–$5000 range. The combination of complexity, dubious quality control, and critical rust means that XJ6s are tricky and relatively expensive to restore, not to mention it’s very tough to convince potential buyers that they will stay fixed. And given that even #1-condition, concours-quality examples bring prices only in the low $20,000s, recouping the cost of a full restoration is often a pipe dream.

XJ6 Launch NY Hilton 1968
Jaguar
XJ6 Launch NY Hilton 1968

1973-91 Jaguar XJ12

Compounding problems, the Series I XJ12 which followed—23,564 were sold from 1973–91—used the 5.3-liter V-12 engine found in the Series III E-type. Air conditioning was standard, but no manual gearbox was offered. Jaguar raised the XJ6 and XJ12 front bumpers to meet U.S. regulations in the 1974 Series II, and fuel-injection replaced the V-12’s four carburetors, pumping the engine from 244 hp to 285 hp in 1975. The XJ6 was fuel-injected from 1978 and both were LWB-only from 1974. A two-door coupe was introduced in 1975, but door seals leaked, the body flexed, and it is rare today (production amounted to 6487 XJ6s, 1855 XJ12s).

The final redesign of the original XJ occurred in 1980 with the Series III. Pininfarina raised the roof of the rear and smoothed out the rear fender line. Quality control finally improved for 1982, when the excellent HE V-12 was introduced; before that it bordered on sabotage. The XJ-40 replaced the XJ6 for 1987, while the XJ12 soldiered on until 1991.

1972 XJ12 Series I
Series I XJ12

Stick with the six, but the engine is just the tip of the iceberg

Enthusiasts gravitate to the six-cylinder cars because they are easier to work on—and you will be working on them, so plan on it. The V-12 is more difficult to maintain, and overheating issues were exacerbated by catalytic converters raising under-hood temperatures to crematorium levels. Rubber fuel hoses in the V never stood a chance.

Ray Nierlich is a lifetime Jaguar expert, and has been Dr. Jaguar in Newport Beach for 25 years. A machinist who makes special tools when necessary, he views Jaguars with the exasperation associated with a beloved child with a sugar addiction. He’s used to crises.

Nierlich says the Achilles heel of all years is head gasket sealing. Blame an overly complicated cooling system, questionable head gasket material, and immersing poor head studs in coolant. The block deck was also weakened with each series. Air conditioning can raise cylinder head temperatures, and S1 A/C never worked well, although S2 and S3 systems are better. All are R12 and must be converted to R134, unless you want to buy expensive Freon.

Sir William Lyons with XJ6 Series I
Jaguar
Sir William Lyons with XJ6 Series I

No left-hand-drive four-speed cars were sold in the U.S. (partly because there’s nowhere to put your clutch foot—the wheel arch intrudes), and automatic transmissions are pretty dismal. Early cars had a tough but leaky Model 12 iron case Cruise-O-Matic, while the 1974–79 Model 65 was a flimsy alloy box from a Ford Maverick. The 1980–87 Model 66 is slightly better, but all are only three-speeds. The XJ12 got GM’s superior T400 Turbo Hydramatic in 1977.

Electrics illustrate all the Lucas jokes, Nierlich says. Series I cars are merely antiquated, but S2 switches routinely fall apart and electronic ignitions fail. Plastic starter relays self-combust and pressurized fuel lines can spray fuel onto ignition parts on start-up. If you hear a “pop,” never open the hood without a fire extinguisher. The 1975–78 XJ6s featured sticking Stromberg auto chokes, which melted catalytic converters. Inertia safety switches stranded owners.

Series II XJ12 Grille
V-12 engine in XJ Sedan

At the bottom of the barrel are the early S3 cars in 1980–81. Things brightened up in 1982, but then in 1984–85 Jag forgot to machine the rear main journal correctly and the engine spun the rear main bearing around 60,000 miles—with no warning.

Light at the end of the tunnel?

Beginning in the 1970s, frustrated owners started fitting Chevrolet V-8s into the worst XJ6 sedans, although they are a poor substitute. The wiring harness must be modified, sending units swapped to make gauges work, and legal smog gear fitted in California. Plus V-8s vibrate worse than straight-sixes, and nobody trusts a mongrel. Besides, if you can't work on it, who will?

XJ Series II front 3/4
Jaguar
XJ Series II

A glimmer of hope presents itself in the case of low-mileage, immaculate examples. One-owner cars represent the best bet; no matter how many miles, deferred maintenance shouldn’t be an issue. Bring a Trailer set a record for an XJ6 sale in March, when a seller in Evanston, Illinois, sold a two-owner, 7300-mile 1986 sedan in Regency Red for $21,000.

Everybody agrees that the XJ6 was a terrific car when it was new; the trick is to find one now.