Jaguar XJ40, X300 and X308, including XJ8 (1986 to 2003)

The XJ40 was the first all-new Jaguar saloon since the original XJ6, approved in 1980 under British Leyland and finally launched in October 1986 after Jaguar had regained its independence. It brought the AJ6 straight six, a more angular body and a great deal of new electronics, some of which gave early cars a poor reputation. Ford bought Jaguar in 1989 and steadily improved the car, adding a 6.0 litre V12 in 1993.

In 1994 the X300 replaced it. It was a heavily reworked XJ40 rather than a new car, with a curvier body recalling the Series 3, the improved AJ16 six, a carried-over V12 and the first supercharged XJR. In 1997 the X308 followed, again using the same basic shell but with Jaguar's new AJ-V8 engine, a fresh interior and the XJ8 name. Production ended in 2002, with the aluminium X350 taking over.

All three share a comfortable ride, a quiet cabin and the traditional Jaguar blend of wood and leather, and the supercharged cars are seriously quick. Running costs and electrics are the usual worries, but later cars in each family are generally better built. Daimler versions (Daimler Six, Double Six, Eight and Super V8) and long-wheelbase bodies are part of the story.

• Years: XJ40 1986 to 1994; X300 1994 to 1997; X308 1997 to 2002 (some registered into 2003).
• Body styles: four-door saloon; long-wheelbase versions (X330 for the X300 era, and LWB X308).
• XJ40 engines: AJ6 six of 2.9 litres (single cam, about 165bhp), 3.2, 3.6 and 4.0 litres (twin cam, the 4.0 about 235bhp in UK form); 6.0 litre V12 from 1993.
• X300 engines: AJ16 3.2 (about 216bhp) and 4.0 (about 245bhp); supercharged 4.0 XJR (about 321bhp); 6.0 V12.
• X308 engines: AJ-V8 3.2 and 4.0; supercharged 4.0 XJR (about 370bhp).
• Gearboxes: ZF four-speed automatic (most XJ40 and X300 sixes); Getrag five-speed manual (rare); GM four-speed automatic on X300 V12 and XJR; five-speed automatic on X308, with a Mercedes-sourced unit on the XJR.
• Production: Classics World gives about 92,000 X300s and only about 3,400 6.0 V12 cars of that generation. Classic & Sports Car gives 6,547 X300 XJRs and 15,703 X308 XJRs, with only around a hundred manual X300 XJRs. No reliable XJ40 total was found in the sources used.

• 1986: XJ40 launched as XJ6, Sovereign and Daimler with 2.9 and 3.6 engines; semi-digital instruments; optional self-levelling rear suspension.
• 1988: XJR 3.6 sports version.
• 1989 to 1990: 4.0 replaced the 3.6 and analogue dials replaced the digital display; 3.2 replaced the 2.9; sport mode for the automatic; improved door handles and electrics. Sources differ by a year on these dates, partly because of model year conventions.
• 1990: a more reliable braking system replaced the early pressure accumulator set-up. During the XJ40's life the rear brakes also moved from inboard to outboard.
• 1992: battery moved to the boot.
• 1993: 6.0 V12 XJ12 and Daimler Double Six; 3.2 S and 4.0 S models; airbags.
• 1994: X300 introduced with AJ16 sixes and the supercharged XJR.
• 1995 to 1996: long-wheelbase X330 bodies, later standard on the 4.0 Sovereign.
• 1997: last V12s built; X308 launched with V8 engines only, oval-trimmed dashboard and new seats.
• 1999 to 2000: equipment upgrades; XJR gained drive-by-wire throttle. Steel cylinder liners replaced Nikasil around August 2000.
• 2001: XJR 100 limited edition for the Lyons centenary.
• 2002: XJ8 SE run-out models; production ended late that year.

Bodywork and structure

• XJ40: front subframe around the upper wishbone mounts, suspension turrets, front bulkhead (lift the scuttle trim on boot-battery cars), inner and outer sills, the inner wing to sill joint behind the front wheels, door bottoms, rear arches and the panel above the rear bumper.
• X300 and X308: front chassis legs, door corners, rear arches, inner wings and footwells. Alloy bumper mounts can corrode badly.
• All: bubbling around the front and rear screens is costly to cure. A bolt-on radiator support panel is a cheaper fix.
• Check the boot opens with the key; seized locks and disabled valet switches are known.
• Plastic sunroof tracks on X300s can break.

Engine

• AJ6 and AJ16 sixes: a growl or rattle at a cold start points to the upper timing chain tensioner. Head gasket failure is uncommon but look for sludge under the oil filler cap.
• X300 sixes: cracked cast iron exhaust manifolds, carbon build-up and a sticky throttle, and weak thermostat housings and water pumps.
• V12: overheating can loosen valve seats. Look for clean coolant at the right strength and no leaks.
• AJ-V8: early engines used Nikasil bores that wore on high-sulphur fuel; many were replaced under warranty. The plastic-bodied timing chain tensioners can fail with severe consequences, and the water pump impeller can break up. Ask for proof that tensioners and pump have been upgraded.
• Supercharged cars: the supercharger has its own oil and it is often neglected.

Gearbox and drivetrain

• Automatic fluid should be red, not black or burnt-smelling. A car stuck in Park may have a failed brake light switch or interlock.
• GM-boxed cars can whine in first and reverse. Getrag manuals get noisy and have dual-mass flywheels that are no longer available new.
• A whining rear axle is common at high mileage. Look for pinion seal leaks and a perished propshaft coupling. On X300 and X308 the driveshafts act as suspension links, so wear in their joints affects handling.

Suspension, steering and brakes

• Early XJ40 self-levelling often fails; many cars have been converted to conventional springs and dampers. Ask for invoices showing both were changed.
• Worn front wishbone bushes, rear subframe mounts and damper bushes cause clonks and vagueness.
• Early XJ40 brakes use a pressure accumulator; a persistent warning light suggests trouble. ABS faults on later cars are usually sensors or corroded rings.
• Adaptive dampers on some X308s are expensive to replace. Steering racks can leak.

Electrics and interior

• Test every switch, the climate control, central locking, electric seats and the steering column adjustment. Door lock solenoids and early exterior handles fail.
• Headlinings sag on all three. Sports seat bolsters wear.
• Air conditioning faults rarely end with a simple regas. Pre-1990 cars used the old R12 gas.

Identity and paperwork

• Check the badge matches the engine. XJR and Daimler badges are easy to add.
• Confirm Nikasil status on early V8s from engine numbers and warranty paperwork.
• A long-wheelbase body should be confirmed from the chassis records.

Mechanical parts are mostly easy to find through Jaguar specialists and breakers, though some trim, early XJ40 electronics and X300 manual gearbox parts are scarcer. The Jaguar Enthusiasts' Club (https://jec.org.uk/) has model forums and can lend tools for V8 tensioner work, the Jaguar Drivers' Club (https://www.jaguardriver.co.uk/) runs model registers, and the Daimler and Lanchester Owners' Club (https://www.dloc.org.uk/) covers Daimler versions.

• Have the timing chain tensioners and, on V8s, the water pump been replaced, and is there a receipt?
• Does a V8 have its original Nikasil engine, a warranty replacement, or a steel-lined unit?
• When were the gearbox, differential and supercharger oils last changed?
• On an early XJ40, has the self-levelling suspension been converted, and how?
• What rust repairs have been done to the sills, chassis legs and screen surrounds?