Jaguar XJ6 and XJ12 Series 1, 2 and 3, with Daimler Sovereign and Double Six (1968 to 1992)

The XJ6 was the saloon that Sir William Lyons used to replace a sprawling range of Jaguar four-door cars with a single model. Launched in 1968, it took over from the 240 and 340, the S-Type and the 420, and it was the last new Jaguar to appear under his direct control. It used a monocoque shell, Jaguar's independent rear suspension and disc brakes all round, and at first came with the long-serving XK straight six in 2.8 and 4.2 litre forms. The 5.3 litre V12 arrived in 1972, making the XJ12 one of the fastest four-door cars of its day.

Daimler versions were sold in parallel as the Sovereign (six cylinder) and Double Six (V12), with fluted grilles and richer trim but the same mechanical package. The design was revised as the Series 2 in 1973 and restyled by Pininfarina as the Series 3 in 1979. Six-cylinder cars gave way to the XJ40 in 1986 and 1987, while the V12 saloons carried on until 1992.

On the road the appeal is ride quality and refinement. The cars soak up poor surfaces, the cabins are quiet apart from some wind noise around the front pillars, and the power steering is light but short on feel. Reputation varies by era: the Series 2 suffered from British Leyland build quality, while late Series 3 cars are widely regarded as the best made. Rust is the defining issue for every series.

• Years: Series 1 1968 to 1973; Series 2 1973 to 1979; Series 3 1979 to 1992 (six-cylinder Series 3 ended 1986 to 1987, V12 saloons later).
• Body styles: four-door saloon in standard and long wheelbase; two-door pillarless coupé (XJ6C, XJ12C and Daimler equivalents) in the Series 2 era only.
• Engines: XK six of 2.8 litres (about 140bhp), 3.4 litres (from 1975) and 4.2 litres (about 180bhp in early UK form); 5.3 litre V12, around 253bhp at launch on carburettors, later fuel injected with up to about 295bhp in Series 3 form, according to Hagerty.
• Gearboxes: four-speed manual with overdrive on early sixes; five-speed manual on Series 3 sixes; Borg-Warner three-speed automatic, with a GM400 automatic on V12s from 1977.
• Daimler models: Sovereign 2.8, 3.4 and 4.2; Double Six; Vanden Plas versions with extra trim.
• Production: published totals disagree widely. Hagerty says almost three quarters of a million Series 1 to 3 cars were built, while a production table on the Jag-lovers site adds up to under 300,000 and has gaps. The Daimler and Lanchester Owners' Club publishes Daimler-only figures. Treat any total with caution.

• 1968: XJ6 2.8 and 4.2 launched; Daimler Sovereign followed in 1969.
• 1972: XJ12 and Daimler Double Six introduced; long-wheelbase body added, about four inches longer in the rear.
• 1973: Series 2 with raised front bumper, shallower grille, revised dashboard with stalks instead of rocker switches. Short wheelbase saloon dropped from late 1974.
• 1975: 3.4 litre six replaced the 2.8, which had a fragile reputation. Two-door coupé on sale for about two to three years.
• Mid to late 1970s: V12 gained fuel injection; UK six-cylinder Series 2 cars stayed on carburettors.
• 1979: Series 3 with higher roofline and more glass, flush door handles, heavier impact bumpers, vertical grille slats and a five-speed manual option. The 4.2 gained fuel injection; the 3.4 kept carburettors.
• 1983: Sovereign name moved to the top Jaguar model and Daimler badging moved upmarket.
• 1986 to 1987: six-cylinder saloons replaced by the XJ40.
• 1992: final V12 Series 3 saloons. Sources give end dates between 1990 and 1992 for Jaguar and Daimler V12 versions.

Bodywork and structure

• Inner and outer sills, closing panels, floorpans and the box-section chassis members under the floor.
• Front subframe mounts and, especially, the rear suspension mounting points. Get underneath with a torch where the auction house allows it.
• Bubbling around the front and rear screen surrounds. Water trapped under the rubbers rots the frame, and proper repair means removing the glass and much of the dash.
• Front wings around the headlamps, valances front and rear, door bottoms, wheel arches, bonnet hinges, radiator crossmember, boot floor and spare wheel well.
• Fuel tanks (twin tanks in the rear wings) and their surrounding metal.
• Fresh paint deserves suspicion. Look for overspray in door shuts and at the join between inner and outer sills. Coupés have unique sills and doors that are scarcer than saloon parts.

Engine

• XK sixes use some oil; that is normal. A timing chain rattle at idle or as revs rise means a big job.
• Oil pressure should be healthy at speed, though factory gauges are not reliable. Expect a low reading at a warm idle.
• Rear main oil seal leaks are common on both the XK and the V12.
• Original 2.8 engines had a reputation for holed pistons and are now rare.
• The V12 needs a perfect cooling system. Look for coolant stains, a weak antifreeze mix and signs of overheating. A single dead cylinder can feel like only a slight misfire, so listen carefully if the engine is started.
• Early Series 2 cars on carburettors can be hard to set up; ask what has been done.

Gearbox and drivetrain

• Borg-Warner automatics are durable. Harsh changes often point to old fluid or a perished gearbox mount.
• Manual cars are robust, but the clutch requires engine removal.
• Check for oil from the differential, which sits within the rear suspension cage.

Suspension, steering and brakes

• The independent rear suspension is expensive to overhaul. Clonks or a loose feel point to worn bushes and radius arms; many cars need a rear rebuild soon after purchase.
• Front clonks are often shock absorber bushes. Power steering racks wear and leak.
• Inboard rear brakes are awkward to service; look for oil contamination around the cage.
• Matching quality tyres suggest care; uneven wear suggests suspension trouble.

Electrics and interior

• Wood veneer usually needs professional restoration; leather can often be revived.
• Test all window switches, door locks and the fuel tank changeover switch.
• Original air conditioning rarely works well, and its parts sit deep in the dash.
• Damp carpets, a sagging driver's seat or welding burns indicate neglect.

Identity and paperwork

• Confirm the series, engine and Daimler or Jaguar badging against the V5C and chassis plate. Engines and badges are sometimes swapped.
• Odometers can be altered, so match mileage to MoT history and bills.
• Coupés and Series 1 cars are worth confirming as genuine; a saloon converted to look like something else is possible.

Body and mechanical parts are widely available through Jaguar specialists and the clubs, and repair panels exist for most structural areas, although wings and doors can be scarce and coupé panels harder still. Most servicing can be done at home, with the V12 the exception. Owners' clubs include the Jaguar Enthusiasts' Club (https://jec.org.uk/), the Jaguar Drivers' Club (https://www.jaguardriver.co.uk/), which runs model registers, and, for Daimler versions, the Daimler and Lanchester Owners' Club (https://www.dloc.org.uk/). The Jag-lovers online community (https://jag-lovers.org/) holds a large archive of technical information.

• When were the sills, floors and rear suspension mounts last inspected or repaired, and are there photographs?
• Has the rear suspension been rebuilt, and when?
• Is there a history of overheating, head gasket work or timing chain replacement?
• Does the engine match the badging and the registration document?
• What do the MoT records say about corrosion advisories over recent years?