These days a Jaguar XJ6 is a highly sought-after classic. Values of all – but especially the 1968-73 Series I models – have increased significantly in recent years, and all the signs are that this trend will continue. However – and this is important – values are very much dependent on condition; minters of the right model and spec can sell for five figure sums, but the roughest ones are only worth just a few hundred. And while a genuinely good XJ6 will be a delight to own, drive and look after, a tired one could be trouble with a capital ‘T’. 

Sadly, when there’s a big price differential between good and bad examples, there’s a greater incentive for some sellers to make a car look better than it really is.

Before we look into the practicalities of picking a good car and avoiding a dressed-up old dog, let’s sort out the various models under consideration.

The original car, now known as the Series 1, was made between 1968 and 1973, with a choice of 2.8- or 4.2-litre six-cylinder engines. Most key mechanical components were developments of existing Jaguar units including the independent rear suspension and all-round disc brakes. Other traditional Jaguar features included twin fuel tanks and a dash arrangement incorporating four circular minor instruments in the centre. The new car was bigger than the S-type and 420, both of which it replaced, but smaller than the 420G, which remained in production until 1970. From 1972 a long wheelbase version – four inches longer and with a consequent increase in rear legroom – was offered as an option.

Today, the Series 1 is the most desirable of these cars – and easily the most valuable – as the purity of the original design is very highly regarded.

The Series 2 arrived 1973. The main change was a raised front bumper and consequently the Series 2 sports a modified main grille with two smaller ones under the bumper. Inside, the dash and control arrangements were simplified – some had criticised the air-con/heater controls on the Series 1 as overly complex – and there were also changes to switchgear brought about by changing safety regulations.  Initially the Series 2 was also offered with either a standard or LWB bodyshell, but from late 1974 the ‘standard’ length was withdrawn. Soon afterwards, a two two-door coupé – based on the shorter wheelbase – became available. This had been ‘previewed’ in 1973, but difficulties with achieving satisfactory weather sealing meant the launch was delayed. In the event, the coupé wasn’t massively popular and discontinued after just two years. Also in 1975 the 2.8 engine – slow and starting to develop a reputation for fragility – was replaced by a 3.4-litre unit.

The Series 2 has traditionally been the least popular XJ6, mainly because its production spanned the worst years of British Leyland, with the consequent quality issues. This association wasn’t helped by the adoption of several colours that looked very similar indeed to the most readily identified British Leyland hues: Jaguar’s ‘Harvest Gold’ wasn’t called that or quite the same, but it was so close, and so different to anything anyone else offered, that this really didn’t matter.

Today the situation is slightly different, as age and ‘natural  wastage’ has meant the remaining Series 2 Jags were either put together properly to start with, or cars that subsequent owners have spent time and effort on getting right. Additionally, if you want a coupé then you’ve no option but to buy a Series 2.

The Series 3 arrived in March 1979. These retained the same basic look, but the cabin top had been restyled by Pininfarina to incorporate narrower door frames and a greater glass area. The front-end was also restyled with thicker bumpers, and a simpler grille with only vertical vanes. At the back, the reversing lights were incorporated into the rear light clusters. The front door windows were now single-glass units without separate quarterlights, and once again there were internal changes.

As before, the engine choices were 3.4 or 4.2 ‘six’ and 5.3-litre V12, but all 4.2 engines now came with Lucas fuel injection as standard (this had been fitted to USA cars since 1978) leaving only the 3.4 (which wasn’t sold Stateside) with carburettors. The manual transmission option was now a five-speed manual rather than a four-speed with overdrive. This had actually been introduced the previous year though few Series 2 Jags were sold with one. It wasn’t widely publicised either, as the ‘box in question was a Rover item, as used on the TR7 and SD1; the first example of Jaguar sharing major mechanical components.

For the first time, a factory-fit sunroof and cruise control were offered with the Series 3. There was a restyle in late 1983 with the ‘Sovereign’ name – hitherto the sole preserve of Daimler – being used for the range-topping Jaguar model. The six-cylinder cars were discontinued in favour of the XJ40 range in 1986, but the V12 remained in production until the end of 1990.

The Series 3 was introduced just before Sir John Egan’s arrival as chairman of Jaguar in 1980. Though Jaguar remained within BL for most of Series 3 production, quality improved dramatically during the Egan era. Just as importantly, the public’s perception of the brand improved. Many people also thought the XJ40 was a tad too ‘electronic’. Consequently, the Series 3 became something of a sought-after classic while it was still young enough for there to still be some decent low ownership and well-maintained examples for enthusiasts to buy. The car has also proven to be the best-built of all these cars. Fuel injection also makes the Series 3 the most fuel-efficient of the sixes.

Though most people think of these cars as Jaguars they were all available as Daimlers too, and there are no differences between the Jaguars and Daimlers that make the latter worse cars. Prices though can be a bit lower, and there’s also some anecdotal evidence that, while the Daimlers are rarer than Jaguars, a higher percentage of the cars that do survive are good ones…

The first Daimler-badged XJ6 arrived in 1969, replacing the Jaguar 420-based Sovereign and using the same name. In 1972 the Daimler Double Six (Daimler’s version of theXJ12) arrived, along with a higher-spec Vanden Plas version the first of the XJ6/XJ12 range to use the longer wheelbase. The Daimlers then followed the Jaguars into Series 2 form in 1973 (including the two-door coupé from 1975 to 1977) and then in 1979 the Daimler Sovereign went into Series 3 form. As already noted, from September 1983 when Jaguar was privatised and thus no longer able to use the Vanden Plas name for its top model, the Sovereign name was ‘transferred’ to Jaguar and the Daimler name used for the top model: The six-cylinder range thus comprised  Jaguar XJ6, Jaguar Sovereign and Daimler 4.2. All these were discontinued in 1986. However the Double Six remained in production alongside the Series 3 XJ12 until 1991.

Traditionally, most buyers have much preferred the six-cylinder cars to the twelves – even the most efficient V12 variant struggles to beat 14-16mpg overall. The V12 is also something of a specialist unit – it originated as a racing engine. While it’s not inherently weak, it does demand regular and informed maintenance and repairs are rarely cheap.    

There is another side to all this: V12s tend to have covered lower mileages, and consequently good ones can be very good indeed. It’s also a fantastic engine – a truly superb piece of engineering. We’d say that if you are looking for a ‘high days and holidays’ car that won’t do more than 1500-2000 miles a year anyway, it might well be worth sitting down with a calculator and working out how much more, in money terms, a V12 will actually cost you. You might be pleasantly surprised…

As far as the sixes go, most buyers much prefer the 4.2-litre unit. As already noted, the 2.8 engine has a reputation for weakness – holed pistons in particular. So much so that a surviving 2.8 still with its original engine is now something of a rarity. The 3.4 more durable, but neither smaller unit will save you much on fuel.

Having said that condition is far more important when assessing any of these cars, so without further ado let’s look at how to identify a genuinely good example.

First, try to find out where a car has come from and where it’s been. A long-term previous owner is usually a good sign; such a person is more likely to have taken the long-term view and looked after the car in the best – as opposed to the cheapest – way possible. A sheaf of repair bills from recognised specialists is also reassuring. Equally, I wouldn’t necessarily be concerned if the car has been DIY-maintained. Contrary to popular belief these are cars you can maintain on your driveway (apart from the V12 engine) if you’re mechanically minded. Plus, many owners actually find that some parts being a little complex makes the task more enjoyable.

Interior condition is also a pretty good guide to how a car has been cared for. Don’t be too concerned about normal wear and tear to things like the seats and carpets – that’s normal and just shows the car’s been used. What you’re watching for is signs of hard use – what, for example, could cause the headlining to be holed.

How many of the minor electrics work properly is also a very good guide to how good a car really is. Nowadays working original air-con is very unlikely but things like one or more electric windows that don’t work at all may be a sign of someone who hasn’t kept on top of the car as they should. On the other hand, if only the rear windows are affected, it may simply be that the owner hasn’t had cause to use the rear seats.

Tyres are another good barometer; are they a good matching set – ideally all round but on an axle at the very least – of a brand you recognise and trust, or are they a mishmash of various types?  Uneven wear can suggest a suspension wear issue.

As always, body condition is the most critical aspect of buying. Proper repairs are time-consuming and consequently expensive, and while panel availability is pretty good (all things considered) prices aren’t exactly low. LWB saloon sills, for example, are £160 apiece, and coupé sills are over £250. Additionally, wings, doors and the like are scarce, and it’s normally a case of repairing what you have with let-in sections.

But before you get into specifics, look at the car as a whole. Chances are it will have had some paintwork; how well has it been applied and how long ago? An older respray is potentially okay if it still looks good, as chances are what’s underneath is basically okay at the very least. Fresh new paint could be covering up pretty-much anything.

As well as all the usual rot-spots on unitary construction cars of this type, look out for bubbling around the front and rear screen surrounds. This is caused by moisture being trapped by the screen rubbers, and once you’ve got the screen out – which you have to, in order to repair this area properly – you’ll almost certainly find the rot is much more widespread than was at first apparent. Additionally, you’ll need to remove most of the dash to gain welding access – again a very major task.

Besides looking bad, rot here can lead to water leaks into the cabin, which, besides being unpleasant, will soon cause serious damage to the trim. Damp in the boot is normally caused by the rear window seal allowing water that gets past to drip down.

What matters most of all though is structural condition. Here the usual rot-spots are sills, floorpans, underfloor chassis members, front subframe mounts (oil leaks from the engine usually protect the frame) and, perhaps most problem-prone of all, the rear suspension mounting points. Ready-made repair panels are available for all these, so really it’s a case of assessing how well anything has been fitted.

I’ve already mentioned the interior briefly. Specific weaknesses to look out for are a collapsed/sagged driver’s seat, water ingress, ‘burn marks’ where welding has been carried out without stripping the car properly, and general tattiness. Expectations here do vary somewhat; some people really want as close to perfection as they can find, others reckon that a few signs of general wear add to the car’s character and gives the car a bit of genuine patina. Similarly, although Jaguar saloons do have something of a ‘cigar and whisky’ image, the smell can be off-putting and is actually quite difficult to eliminate.

Finally, try the air/ventilation system. As already note, operational air-con is very unlikely, but ensure the various flaps and blower motors direct the air as they should. Faults here can be extremely time-consuming to fix, as much of the kit is buried deep inside the dash. 

First the good news; with the exception of the 2.8 six, the engines are all basically good units. They all burn a bit of oil though. However unlike on contemporary OHV engines, you shouldn’t ignore a bit of timing chain rattle – audible under the bonnet at idle and as the revs are raised – as the chains are much longer and can break; and rectification is a major job. It’s normal for oil pressure at warm idle to barely register, but it needs to be at least 40psi at speed. Double-check a low gauge reading before condemning the engine though as factory gauges are not that reliable. The V12 is tough too, but one cylinder out of 12 not working will feel like a minor misfire on a lesser car! Check a V12 too for signs of overheating; the engine was shoehorned in, and the cooling system has to be in tip-top condition.

Various Borg-Warner auto ‘boxes were used; all are tough, as were the manuals, though these aren’t especially user-friendly and a clutch change is an engine-out job.

Front suspension ‘clonks’ are often caused by nothing more than worn shock absorber bushes. The rear suspension can become soft and soggy with age, but because it deteriorates slowly an owner often won’t notice until they drive another car. If there’s no evidence that it’s been done already, expect to rebuild the back end soon after purchase – chances are it’ll transform the car. Power steering racks wear and can fail, but exchange replacements are available for around £30.

As I hope I’ve shown, the secret here is to go into the process with your eyes wide open. What are the panel gaps like? Where has the car been painted, and where’s the overspray? What about the ‘hidden’ panel joins – i.e. within the door shuts and where outer and inner sills join?

But above all, does the car look and feel like someone has cherished and looked after it, or has it been repaired as cheaply as possible? If the former, you’ll probably be okay, though as with most ‘new to you’ cars you may have to spend a bit in the first year or two bringing things up to your standard. With a maintained on the cheap example though, you’ll end up covering the previous owner’s savings – many times over!