Conceived in the early 1960s as a means to consolidate Jaguar’s extensive saloon range into one basic model line, the XJ6 of 1968 quite literally redefined the luxury car by setting new standards in both refinement and driver involvement. This really was to be one of the greatest British cars of all time.
This range of Jaguar saloons provided the back bone for Jaguar’s production from the 1960s to the 1980s and as such encompasses all the troubles that the British car industries were experiencing during this era. The Jaguar name was brought to its knees in terms of production and quality in the mid ’70s and the cars produced during these years reflect these facts. Sir John Egan bought in massive changes in the early ’80s which helped to bring back in reliability but this was too late for the Series 2 and early Series 3.
The Jaguar XJ Series 1 was a significant step forwards from previous saloons but was still a complex vehicle both in terms of systems and bodyshell. The mechanical aspects of the cars were very similar to Jaguar S-Types and Mk X but had been further refined over the years.
The XJ bodyshell followed on for the earlier saloons in terms of a monocoque structure with a front subframe and rear subframe or “cage” supporting the relevant suspension systems. The vast majority of all of the suspension fixings were designed to bolt to these subframes and these subframes were then fully isolated on rubber mounts from the bodyshell. Even the engine was mounted onto the front subframe with rubber mounts to further isolate vibrations and transmitted noise from the bodyshell.
The XJ bodyshell is a complex structure in itself and there are many places where corrosion can start. Typical places are front radiator cross-member, front shock absorber mounting areas on inner wings, front jacking points, sills, rear jacking point and radius mount area. The jacking points on the bodyshell really should not be used except in an absolute emergency as they are not strong and any use invariably damages the paint protection allowing the rust to get a hold. This further weakens the jacking point leading to more damage if it is used to support the car.
Rear valance, rear wheel arches, bottom of front wings and headlight areas are all (relatively visible) potential rust spots as well as the windscreen apertures on Series 3s. If you are having a windscreen replaced on a Jaguar Series 3 always check the aperture before the new screen is fitted to ensure there is no serious corrosion present. If there is any level of rust try to get this repaired otherwise it will become a major problem in the future. Bottoms of the doors can also corrode badly if the drain holes become blocked.
The XK engines were reliable but the passage of time always affects these things! The straight 6’s 2.8, 3.4 and 4.2 litres were all straightforward and relatively easy to repair but overheating could lead to further issues. Lack of correct servicing and coolant changes could lead to a number of issues around overheating. Later Series 3 engine blocks were modified to allow for further cooling at the head gasket area. Over heating of the heads could lead to movement of the bucket guides and this then means a reasonable expensive machining operation to correct. The cylinder head studs ran deep into the waterjacket of the block and on cars with insufficient coolant to prevent corrosion these studs corrode away to almost nothing and can shear off leaving a machining problem to remove the remaining piece of stud some 7” inside the block.
All the V12 engines can suffer from this type of problem as the engine is designed with wet liners and is therefore very susceptible to problems from corrosion if the coolant was allowed to degrade. The head gaskets and cylinder head studs are almost completely exposed to coolant and if corrosion sets in, the heads can become seized on the studs and the head gaskets can completely fall apart leaving just the fire rings around the cylinders and the outside edge of the gasket. All the debris from the head gaskets breaking up restricts the water jacket in the block, especially at the back of the block where the water pump flow is slowest. Overheating V12s can lead to valve seats falling out of the head and further major mechanical problems as a result.
Internal corrosion to the blocks on Jaguars leads to underlying tendencies to overheat whenever the external temperature rise unduly, this is often put down to radiators, cooling fans etc but can remain as an unsolvable problem due to the fundamental nature of the corrosion.
Radiators, whilst they can become blocked and inefficient, are generally ok but problems do arise on later cars and V12s where there are 2-3 radiators mounted one in front of the other. Here road debris can build up between the radiators and lead to large areas of the radiator being simply unavailable for cooling. Again the problems show themselves on hot days with the air conditioning running and this is typically when the car struggles to cool itself sufficiently.
The low engine oil cooler is a case in point on Series 3 XJ12 as this invariably gets a great deal of debris built up between it and the engine coolant radiator. This leads to increased coolant temperatures and this increases the pressures and temperatures of the air conditioning system placing further unnecessary loads on the pipes, seals and compressor of this system. On the later Series 3 the engine bays are crowded to say the least and any build up of debris between the radiators can cause significant problems.
PLEASE keep all Jaguars running on the correct levels of coolant. This is by far the best way to maintain the cooling systems!!
Gearboxes are all reasonably reliable with the automatics being somewhat basic 3 speed units. Borg Warner Model 8, Model 12, Model 35, Model 65, Model 66 and GM 400 were all used over the range of cars and are all relatively simple and repairable. The optional 4 speed manual and overdrive was reasonably strong but the later Rover based 5 speed box as fitted to Series 3 suffered probably due to the weight of the XJ. Clutches again were reliable and relatively easy to replace.
Front Suspension and Brakes
The front suspension cross-member provides the mounting for the upper and lower wishbones and steering rack. The cross member is a robust steel fabrication mounted on 4 Metalastic mounts, 2 circular ones at the front, bolting through the chassis rails, and 2 more typical Jaguar V mounts at the rear. Whilst the cross-member in itself does not generally cause problems rust can be an issue especially on the outer uprights that take the upper wishbone mounts. The earlier conventionally painted cross-members seem in many ways to last longer than the later powder coated version which traps moisture under the higher specification finish and this rust can go unnoticed until the damage is critical.
As well as watching out for rust much damage is caused to the cross-member by incorrect jacking. Damage from jacks to the body of the cross-member invariably leads to rusting. These saloons are heavy and if they are being lifted centrally then a suitable pad should be used or the car jacked on each front corner under the wishbone base plate.
Given all the suspension locations and engine are mounted on the cross-member it is clearly critical that the 4 cross-member mounts are maintained in very good condition.
Front suspension is generally extremely robust and requires little in the way of maintenance. However there are a number of obvious upgrades that should be considered. The standard lower wishbone bushes are of very poor design insofar as they are just parallel rubber bushes and can allow the lower wishbones to move fore and aft over time affecting suspension alignment and becoming the source of annoying knocks. Also, with the tendency of the V12 engines, gearboxes and power steering to leak oil the standard wishbone bushes become extremely soft further adding to problems. After market polyurethane “top hat” type bushes provide far better location, better knock prevention and are largely unaffected by years of exposure to oil.
Shimable outer lower balljoints should be replaced for the later style sealed-for-life Lemforder items but beware of the many poor quality copies on the market. Upper wishbone bushes are the Dunlop developed “slipflex” type and are very good but do suffer with age. If they are worn do not replace with after market polyurethane versions but stay with the standard part. They are not easy to check for wear and many XJ-S pass MOT tests despite badly worn lower balljoints and badly worn or seized upper wishbone bushes. Upper balljoints are generally ok but stub axles can become worn, leading to what appears to be excess play in the front wheel bearings which cannot be removed through adjustment of the wheel bearing endfloat.
The power steering racks are generally good albeit getting ever older so leaks are by no means unknown. The 3 steering rack mounts are again a poor design and suffer from softening over time with exposure to oil. This leads to excess movement of the steering rack giving a floating, wandering feel to the car especially at speed. Aftermarket polyurethane replacements are a must but some compliance is required on these bushes otherwise the steel mounting bracketry can crack under the force of the power steering at parking speeds.
Brakes are sensible 4 pot calipers and vented discs on the later cars with the earlier XJs sharing the 3 pot caliper with the later E types etc. Front brakes tend to be fine but are small by todays standards with the front discs being a mere 284mm diameter. This means spirited driving or track day use can lead to a distinct lack of anchors especially if the brake fluid is a little aged!!!!
The universal joints on the steering column can become seized leading to an odd but distinctive feeling through the steering.
Rear Suspension and Brakes
Rear suspension is again very robust and is based on a fabricated lower wishbone with a large alloy hub carrier. The driveshaft provides the final support with the cars mass effectively being supported by the differential output shaft bearings. The subframe/cage is of a much lighter construction when compared to the front subframe. The 4HA Salisbury differential is solidly mounted into the cage and inboard brakes are directly mounted onto the differential output shaft flanges. The handbrake calipers are mounted directly on top of the main hydraulic calipers and are a real nuisance to get to for maintenance.
The 4HA differential is generally strong and comes in many ratios. There is also a limited slip version, known as Powerlock, generally fitted to the V12s. Providing that the differentials are maintained and oil levels are checked regularly then the units are strong and reliable. However oil leaks can develop and if left unresolved can lead to failure. Note that the Powerlock differentials require an oil additive or a specific oil for limited slip differentials in order to keep the plates from sticking.
Rear brakes are more of an issue due to their location and a general failure to understand how the handbrake calipers are meant to work. The main hydraulic calipers are generally reliable and are wholly separate from the handbrake structure. The handbrake calipers are self adjusting and have their own small handbrake pads. However it is not impossible to drive an XJ with the handbrake left on which can lead to overheating, damage to the dust seals on main calipers and failure of the handbrake pads. Changing the discs is not an easy task and lack of care can lead to camber changes on the rear wheels, discs not central in the calipers, wire locking missing and non functioning handbrakes.
Generally if there is a lot of work to do to the rear suspension of a Jaguar XJ then removing the cage in its entirety is a very sensible start. The exhausts may take a bit of separating but after that the job is straight forwards.
Driveshafts are robust and the universal joints strong if regularly greased. Lower wishbone inboard pivots are very reliable providing they are again regularly greased. There are some 12 greasing points on the rear suspension and all need regular attention but please ensure they are cleaned before being greased as otherwise road grit can be forced into the joint, hastening failure.
The outer alloy hub carriers can be a source of problems as setting up both the wheel bearings and trunnions needs care but both are well engineered and capable of giving many years of reliable use. The hub carriers themselves were a cause for concern for a period as some developed cracks just above the trunnion housing and this potential failure should be watched out for.
The rear axle cage is located fore and aft by the radius arms and movement is absorbed by the large bush at the front of the arm. This arm can be severely weakened by rust and the bushes need to be in good condition to absorb the not insignificant loading from the car. This loading is directly transmitted to the bodyshell at this point so a rusty radius arm mount will deteriorate relatively quickly.
Exhausts, Electrics and Fuel
Exhaust systems are generally relatively straight forward but pattern ones can be almost impossible to fit correctly due to inaccurate manufacture.
Fuel systems are relatively straight forwards apart from the twin tank arrangement where there is a return from the engine and the switching of tanks has to also switch the return through solenoids mounted in the boot. The tanks can rust badly both internally and externally and this can cause many associated problems.
Electrics can be problematic depending on year and systems fitted. Air conditioning and heating/cooling is complex and problems can be hard to resolve. Switch gear can be unreliable as mid 70s manufacturing was not quality led. It was not unheard of for front windscreens to leak and this would invariable lead to dubious electrical reliability.
Unfortunately water always seems to find a way into older cars especially given the UK climate! Over time this leads to great damage on a number of fronts and avoiding this degradation is very beneficial to the longevity of any car. Water tends to pool in the lower areas of the car ie footwells and carpets but as the temperature rises on warmer days this moisture evaporates and fills the car with high humidity air. As the day cools in the evening this moisture condenses on the colder horizontal surfaces of the inside of the vehicle such as the inside of the roof and boot panels etc. This condensate then runs off and into sections of the car where water could not normally access and can cause significant problems over time. Bodyshell, electrics, trim and woodwork all suffer this continual degradation over time.
Ideally try and keep all classics in a dry environment with windows slightly open to allow the air to circulate and reduce the moisture levels in the car. Dehumidifiers are also very beneficial over the longer term.
The interior is relatively straight forward but water entry, as described above, to the cabin can lead to seat stitching rotting and to headlining descending in a very inelegant manner! In almost whichever XJ you choose there is a wealth of leather and carpet so a complete interior restoration is a big job in itself.
Overall a great series of cars but probably a full restoration is really not for the beginner. General maintenance and the availability of parts remain good and the robust nature of the overall engineering makes for a daily driver. The XJ is certainly far more complex than a Jaguar Mk 2 but comparable to a 420G or Mk X when considering restorations however end values should also be considered. Preventative measures to maintain the bodyshell and prevent rust would be beneficial for longer term ownership of these flagship Jaguars.