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Jaguar XJ6

Published: 23rd Jun 2011 - 0 Comments - Be the first, contribute now!

Jaguar XJ6

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The XJ6 uses a mix of established Jaguar bits (MK2, SType/ 420) as well as it is own, but is no harder to keep or maintain. However if you have recently bought a car and don’t know its history, check to see how standard the car still is.


Twin overhead camshaft straight six-cylinder. 2.8 (2791cc): 142bhp, 3.4 (3442cc): 161bhp, 4.2 (4235cc): 245bhp


Firing order: 1-5-3-6-2-4 (No. 1 at rear of engine) Spark plugs: 2.8/3.4 Champion UN12Y or equivalent; 4.2, Champion N5 or equivalent (later specification, N11Y; consult Jaguar specialist for correct type). Gap 0.025in. (0.64mm.). Check/clean plugs every 6000 miles (using brass-bristled wire brush); renew plugs regardless every 12,000 miles. Every 6000 miles, check the state of the high tension leads, distributor cap and rotor arm. Sparingly relubricate the distributor’s shaft and mechanical advance mechanism (using a few drops of engine oil) and the cam (apply a smear of high melting point grease). Every 6000 miles, renew the contact points (check condition every 3000 miles and re-gap if necessary); gap to 0.015in (0.38mm); dwell angle 34 degrees±2 degrees). Check condenser and distributor cap for deterioration. Every 6000 miles, check ignition timing. 8.1: compression ratio, 9 degrees BTDC; 9:1 compression ratio, 10 degrees BTDC (mark on crankshaft damper).

Valve clearances

The valve clearances are controlled by replacable shims. Adjustment is not a routine maintenance item (although it is advisable to check the clearances approximately every 50,000 miles) as re-shimming requires cylinder head removal.

Running gear

Every 3000 miles/annually: Examine coil springs, watching for breakage/corrosion, and for rusting around the spring turrets on the front cross-member assembly. Check all shock absorbers for worn bushes and leakage. Examine the upper wishbone bushes, plus the upper and lower ball joints; all these need to be replaced as soon as any wear is detected. Look closely at the rear radius arms; these can suffer from corrosion, and their integral rubber bushes can deteriorate. Fitting new arms is not usually a difficult job. Check the outer, lower rear suspension fulcrum bearings (replacement is a long and involved job). Inspect the anti-roll bar link assemblies; look for worn bushes, also for elongation of the steel washers – which then move along the hexagonal part of the bar. Scrutinise all suspension/steering unit mounting bushes; renew in sets if worn. Examine steering rack gaiters, also those on all ball joints. Assess steering assembly and ball joints for wear. Check for oil leaks fromsteering rack shaft seal. Every 30,000 miles, clean and examine the front wheel bearing assemblies; renew the bearings if any are found to be pitted, worn or noisy. On re-assembly, re-lubricate with fresh grease (but specifically stated as being suitable for use in wheel bearings). Inspect underbody for damage and corrosion including all pipework (plus clips, etc). Check exhaust system for decay, pipe run, security and so on, including all brackets, joints, etc. The electrical system can be fickle due to age and low quality components employed. Check all wiring for decay and poor connections, especially in the engine compartment where heat wreaks havoc over time.


Check the master cylinder and reservoir for leaks (investigate if the fluid level is low), also assess the condition of the fluid. Check brake servo operation and assess hose condition/security. Inspect all fixed and flexible pipework; renew if damaged/corroded. Inspect the front brake pads, discs and calipers; renew the pads if the friction material is badly worn. Replace the discs in axle sets if their working surfaces are seriously worn/scored/corroded. Investigate reasons for uneven pad disc wear. The inboard-mounted rear brakes are very difficult to reach. If the rear axle/suspension assembly is ever removed from the vehicle, it is wise to fully service/overhaul the brakes, and replace leaking oil seals, at the same time. Check in particular for seized rear caliper pistons (more likely on cars which are used infrequently), also for oil contamination on the discs/pads. Ensure that the handbrake mechanism moves freely, and make sure that the rear brakes are locked with the handbrake fully applied (consult manufacturer’s literature). Note that on some examples the handbrake can be adjusted manually; again consult Jaguar literature relevant to your model but Jag handbrakes are notoriously inefficient at the best of times.
Note: The inboard-mounted rear brakes are notoriously difficult to reach. If the rear axle/suspension assembly is ever removed from the car, it is a good idea to fully service the brakes, and replace leaking oil seals, at the same time. Check especially for seized rear caliper pistons (more likely on cars which are used infrequently), also for oil contamination on the discs/pads. At least every 24,000 miles/two years whichever comes first), renew the brake fluid.


Engine: Ideally, change the oil and renew the filter at least every 3000 miles or annually (whichever comes first), having first taken the car for a run to warm the oil and aid the exit of the old lube from the sump. To change the filter element, first release the filter housing drain plug, then take out the housing’s central retaining bolt. Extricate the old filter element, clean the housing in fresh paraffin and dry thoroughly before re-assembling with a new filter element. On assembly, ‘prime’ the new filter with fresh engine oil. Fit a new filter housing seal, and smear this with a little fresh oil. Use a good quality lubricant, with a viscosity rating of SAE15W50 or 20W50 or 20W/60. On completion, ensure that there are no oil leaks, particularly around cam box covers and rear bellhousing.
Sump capacity: Approx. 15 pints (8.52 litres).
Transmission: At each service (at least every 3000 miles), with the vehicle horizontal, check the lubricant levels in the gearbox and the differential. Check for leaks and rectify at once. For specific information relating to the correct oil on your version, check out a classic oil or marque specialist for best modern brews.
Oil capacity, manual gearbox: Approx. 2.5 pints (1.42 litres). For the automatic transmission, where fitted, use Automatic Transmission Fluid (ATF). For information on changing the fluid, please consult Jaguar literature.
Automatic transmission capacity: Approx. 15 pints (8.5 litres).
Differential oil: Duckhams Hypoid 90DL or equivalent (specifically intended for limited slip differentials). Differential oil capacity (approx.): 2.75 pints (1.6 litres).

Cooling system

Regular diligent maintenance of the cooling system is crucially important on an XK Engine. If this is neglected, internal corrosion (particularly within the cylinder head) plus overheating WILL result. Always use high quality anti-freeze mixture containing corrosion inhibitors, and leave in the system all year round to protect against corrosion. Every 3000 miles/annually (whichever comes first), examine the radiator, the fan, and all hoses plus their connections. At least every two years/20,000 miles (whichever comes first), drain the system, flush and re-fill with fresh antifreeze solution (observe the dilution recommendations of the anti-freeze manufacturer). When flushing the cooling system, engage the heater system to ensure that this is also flushed at the same time. Capacity, including heater: Approx. 32 pints (18.2-litres).

Fuel system

Every 3000 miles or annually (whichever comes first), check the state of the air filter element, having first unscrewed the two wing nuts holding the air box housing to the carburettors. Release the air box from the filter housing, and extricate the element. Shake out any loose dirt; change the filter every 12,000 miles regardless. Always wipe out the filter housing with clean rag before fitting new filter element. On completion, ensure that the securing clips are properly engaged. Every 6000 miles/annually, examine all fuel system pipework. Renew at once any dubious looking pipes, unions, clips etc. Every 6000 miles, check/clean the fuel pump filter. At each service, check/top up the oil level in the carburettor dashpots; if necessary, top up the piston spindles with SAE20 oil. At every service, check/re-lubricate the accelerator linkages. At each service, check carburettor synchronisation and mixture settings; use proprietary carburettor balancing equipment. Re-set idle speed; 500-700rpm.

Best Mods

  • XJ6/12 in its original form is possibly still one of the greatest Jaguars ever. Find a short-wheelbase S1 six with manual transmission and it is an absolute delight. Engine developed to eventually become the most powerful production XK engine Jaguar built and with larger inlet valves and fuel injection, it can be turned into a real reliable flier.
  • Granted the 2.8 isn’t a great engine and the easiest power gain is to fit a 3.4 or 4.2 alternative but a lot of hidden performance has been extracted from the 2.8 by using Toyota pistons to take the block to 3.0-litre.
  • Without doubt the 4.2 is the most sensible pick. It can be taken to around 4.5-litres but even in stock guise works well with the later injection as on S3 cars. Even on carburettors it is fine, especially with sorted and fully mapped ignition grafted on.
  • Being a luxury saloon, the suspension is a tad soft but this can be tightened up simply by intelligent use of adjustable dampers, and if needs be, harder springs although bear in mind that the ride will suffer. Really, just bringing the car up to as new spec with OE-spec bushes, dampers etc, together with a full geometry check and realignment will easily transform 90 per cent of old XJs!
  • Similarly tyres on an XJ makes an enormous difference as Jaguar was very choosy with its rolling stock and many old classics cats are running on rubbish rubber. If you can afford it, junk the old stuff and fit the covers originally designed for the car or at least good quality moderns.
  • In principle, the very last XJS steering rack (a sports aluminium unit) could be used but in practice along with JaguarSport or similar chassis mods.
  • Even if you are keeping your car standard, consider fitting an uprated radiator and electric fan. Electronic ignition works wonders as does a simple and extremely cost effective session on a rolling road to set the engine up spot on.
  • In principle a normal overdrive ‘box is as good as a modern five-speeder although that said the Roverderived SD1 five-speed unit found on S3s really suit’s the XJ well and is more usable. Got an auto? Well if you want then a four speeder from the XJ 40 can be grafted on and really does the trick.


  • The XJ6 uses a mix of established Jaguar bits (MK2, Stype/ 420) as well as it is own, but is no harder to keep or maintain. However if you have recently bought a car and don’t know its history, check to see how standard the car still is.
  • Rust is just as bad on the XJ as past Coventry cats. Floors, inner wings, chassis are all vulnerable areas , especially where the IRS is attached by its cage mounts. Regularly remove the rear seat and check for water ingress due to failing rear windscreen seals. At the front, similar poor sealing will rot the bulkheads and floor.
  • A regular jet wash does this cat a power of good as mud and crud collects not only in the wheel arches but also at the join the lower sill area. Check also under the front wings by the headlamps for trapped mud and resultant rusting. It may have been a great car when new but these Jags were never that well protected against rot!
  • Check the bonnet hinges as these can fail or the attachments rot through. Generally it’s the left hand side that suffers most as that’s where the ‘prop’ resides.
  • The XK engine is so well known now that’s it’s a decent DIY bet. Usual service failings are defective electric auto chokes (many fit a switch to cut it out manually on S1s) and leaks (cam boxes and rear crank oil seals), over silent tappets and nosy timing chains, although these can be adjusted for slack.
  • The latter can be changed at home but it’s a swine to do, especially the bottom one which means removing the sump - a big job. However the top ones can be changed by breaking one of the links at the top and attaching the new chain and feeding it through – it’s an old mechanics’ dodge.
  • Tappet adjustment requires a micrometer and shims and means a head off, so budget on a decoke at the same time. Don’t needlessly splash out on hardened valve seats though because Jags have used them for years.
  • You can change a clutch at home but it’s a hell of a job as the engine/box have to be removed as one – or drop the front suspension assembly and neither is no mean feat on the driveway.
  • The IRS suspension is the same as employed on the E-type and its myriad of bushes deteriorate and ruin the car’s poise. But the front suspension design is just as susceptible to this form of deterioration and let go in the same way and are often overlooked.
  • Engine feeling rough - or suffering from clutch judder? It could be knackered engine and gearbox mounts. The engine ones can be mullered by engine oil contamination, especially the driver’s side.
  • Tired springs and dampers go with the territory and if buying used springs then ensure that you are purchasing the correct ones or ride height may be altered. A good XJ should sit all square or slightly raised at the rear. Listing, on the driver’s side is well known although looks worse than it usually is once measured (it should be 6.250-6.375in from lower front sub frame to the ground).
  • Yes we know that the 2.8 engine had a reputation of burning pistons but by now this will have been fully sorted and a good 2.8 is quite a nice driver. Having said that a careful owner will ensure that the cooling system is especially in tip-top shape and that the ignition timing is spot on so not to cause overheating and promote holed pistons.
  • Paint can be a problem on Jags, especially cracking due to the original thermoplastic paints used

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