I’m looking to buy an XJS convertible as a first classic car, and I wanted some advice. I’m looking at either 94-95 for the V12 (6L and better gearbox, plus a small back seat in the convertible), or 95-96 for the 6 cylinder (for the improved AJ16 engine and interior upgrades). My general understanding is that the last few years of the XJS were by far the best from a reliability and drivability standpoint, and I love the long-hood classic British style that you really just can’t get in new cars, at least without spending hundreds of thousands of dollars. I had posted here asking about one last year, that I ultimately decided against given worries about the economy at the time. But life is feeling a lot more stable now and buying a classic car doesn’t feel completely crazy.



As a bit about my life situation, I have a fairly demanding but flexible and mostly remote job, and two small kids that I’d want to drive around in the car. I have a garage and some general mechanical skill (I’ve done basic car repairs over the years, know my way around electronics, and so forth) but this would be my first classic. The goal would be to have a nice GT for driving probably 2k-3k miles a year in nice weather; we have other newer cars for daily commuting. Being able to tinker with it and do some of my own work appeals to me, and is pretty much the only way to own a vehicle like this anyway. But at the same time something really serious, like repairs that would require welding or taking the engine out of the car, would definitely be beyond my ability.



I know the general advice for classic cars like this is to buy the best condition one you can up front and that would of course be the plan. My real question is, how much worse in practice is the 6L V12 from a reliability and maintenance standpoint than the AJ16? Looking around forums and the like—even here, though less so than places like reddit—you get a lot of knee-jerk responses about V12s being nightmares, plus a smaller set of people saying that the V12 if well cared for is actually fairly reliable, and you do often see them come up for sale with well over 100k miles. My understanding is that later 6L is generally sturdier and easier to work on than the older 5.3, and that the main weak points are the Marelli ignition system and rubber hoses cracking with age and heat. What else would one need to watch out for? And how much time would I reasonably need to expect to spend repairing it just to keep it going over the years.



In contrast, the AJ16 is generally talked about as very robust (by 30 year old European car standards at least), and given how much extra space there is under the hood, I’m sure it’s easier to work on. Getting ~20 mpg vs ~12 obviously is also nice, though awful gas milage isn’t a deal breaker for me on its own given the amount I’d drive it and that my daily driver is an EV. I think the fact that the V12 was at least $10k more expensive when new, but used prices given equal milage and condition are otherwise roughly same, definitely says something about the average reputation of the two motors, but again I don’t know how true that is for real ownership.



For those of you who have experience with either version of the car, how much harder to live with would the V12 be? And motor choice aside, how hard is a 94+ XJS to keep on the road otherwise? If the two motors were strictly equal in ease of maintenance I’d pick the 12 for the extra power and the romanticism of driving something properly exotic. But I don’t want a car that would spend most of its time broken or otherwise nearly impossible to keep running decently. As a result, I think at this point I’m leaning toward the 6 cylinder on the grounds that the thing I love the most about this car is the styling and it would be a much easier starting point for me to learn more about working on cars. I’ve seen a handful of “6 vs 12” threads from here over the years, and they're definitely informative, though the situation with things like parts availability may have changed since covid and that’s why I’m asking again.

 

My first 'exotic' 'classic' car was a 94, 6.0 liter XJS Coupe.
It was given to me by someone who wanted to send it to the crusher.
My mechanic experience at that time was break jobs and minor tuneups on older cars.
The car I received had extensive collision damage but no rust.
Just driving it home the first time was a magical experience.
I had some performance cars and sports cars in the past but this was different.
The XJS exhibited Space, Grace and Pace as advertised.
It made me want to learn more about it's history and how to bring it back from the brink.
What I learned was that there were only 209, 94 XJS, 6.0 liter Coupes manufactured in 1994.
But rarity was not a measure of value, and at that time very few expert Jaguar mechanics with 6.0 experience.
I joined a number of Jaguar Forums and they were able to solve many issues, but getting a job as a Jaguar mechanic was vital.
There was a 4.0 coupe available 3000 miles away with good panels and the missing bits I needed.
It turned out to be as perfectly running as my 6.0 but damaged enough that it couldn't be legally driven.
My 6.0 became my daily driver once I replaced the panels and drivers door.
It was as reliable as any car I ever had for years, then it wasn't.
The check engine light came on and couldn't be solved, even by master Jaguar mechanics or specialist shops.
After that there were signs of rust showing up for no apparent reason.
Over all the time I owned it I invested $15k in repairs and diagnostics and I was broke.
I had to let it go to an enthusiast for $1000.
You are looking at a car that is at least 30 years old, so no dealer will touch it.
Independent shops don't have the PDU computer to diagnose it and there are 6 or 7 systems that require a Jaguar PDU.
Those are the Main ECM, the Fuel Injection Module, The Transmission ECU, Brake ECM, Headlight Logic Module, etc, etc, etc.
I seem to recall there are about 50 relays and 100 fuses.
At one time my fuel pumps refused to pump unless I hot wired them past the relays.
This went on for about six months, I replaced a fuel system module and removed the fuel tank to see if the issue was there.
My Master Jaguar Mechanic friend was so frustrated he brought the wiring diagrams home with him.
The next day he told me to check a fuse for something unrelated to fuel pump operation.
Everything worked great after that.
It was a wonderful car to drive, if it was running.

 

Get the 4.0 AJ16. No comparisons between the two cars. The V12 only performs better over 90 MPH and will get about 14 MPG. The 4.0 AJ16's have a wonderful rhythmic inline 6 sound, has better gearing in the transmission and the transmission is far more responsive to driver inputs. The engine management system on the V12 is archaic and lacks much of modem technology like knock sensing and coil on plug ignition which the AJ16 does have. They perform about the same with a slight advantage to the v12 but the AJ16 4.0 feels more responsive is more fun to drive due to lower weight on the nose and will get about 20 MPG. You can get the Andy Bracket for the AJ16 which will advance the ignition timing 2 degrees... that small change really wakes the AJ16 up.

 

I agree with ICSA in your situation. However, you must understand that any Jaguar of this era will require regular maintenance and will need an owner that is prepared to and enjoys fixing, the car. Things like fuel pumps, relays, connectors to electronic components, all will have the possibiity if failing and often, as a search on here will quickly reveal, present problems in identification of the fault. An AJ16 XJS will also often need the Jaguar diagnostic system to identify problems that can arise. For instance this thread:
https://www.jaguarforums.com/forum/x...relays-294760/

Although access under the hood is always tight on a V12 compared with a 6 cylinder car, the earlier V12 Lucas ignition non-ABS cars are the most straightforard to fix, having minimal electronics.

 

Dr_Awesome,

You've done exactly the right thing seeking input an opinions from fellow owners. Here's my 2-pence worth:

As you probably know, an XJS is a wonderful driving experience. Both 4 litre AJ16 and 6 litre V12 engines are sublime, albeit with slightly different characters. I'd suggest there's little performance difference in everyday driving, albeit that the AJ16 feels slightly more accessible and the V12 has a depth of surging torque. I've had an AJ16 for over 20 years, and an early V12 for 6 years.

IMO, the issue these days is not about the inherent reliability of the cars and the engines but the inevitability of age and what that means for ownership and maintenance. Unless you buy a completely rebuilt car for six-figure money, you are going to have maintenance issues during your ownership. Deterioration of cooling systems, fuel systems, engine components, electrical systems and modules are the sad reality of a 30-year old car. And that's where the difference between the 2 engines may become more apparent.

I'd politely suggest that an AJ16 is a much easier drivetrain to maintain today, in terms of reliability, complexity, diagnostic and availability of parts. With it's OBDII system even fault code diagnosis is possible, the knowledge of owners perhaps surpasses even that of V12 owners, and the accessibility of independent workshops may even provide external support, which is fast disappearing for V12s. The V12 is undoubtedly complex and anecdotally, I do not hear of a wealth of knowledgeable workshops for those engines these days on your side of the water.

Unless you're an absolute diehard V12 afficianado, you'll never be disappointed with an AJ16 XJS. It's one of, if not the most, reliable Jaguar engines with great smoothness and performance.

Good luck with your choice

Paul

 

Dr. Awesome,

I have owned my current 96 xjs for ~12 yrs. It is by far the best English sports car I have owned with regards to reliability, looks, comfort etc.
It has won a number of trophies in various JCNA and other competitions.

I have done all the work on this beauty myself but I am going on 81 yrs and washing and polishing is getting to be a chore.

I am thinking of listing it for sale but do not like the idea of going through one of the web sites like BAT or eBay.

the cat has 117k miles but is in like brand new condition. I would be willing to let it go at a reasonable price.

Send me a private message if you would like to discuss further.

Good Luck hunting!

Softball60/Paul

 

Right.

Even with the improvements found in the later models we're still talking about cars that are 30 years old. That's definitely in "life with old cars" territory.

Cheers
DD

 

Hi Everyone, thanks so much for all the information! I think the AJ16 is very likely the best choice for me. I hadn't thought about the distinction between having ODB-II on the AJ16 (and thus easily reading codes) vs. not having that on the V12. Again if they were equally easy to keep running I'd pick the V12 to go all in on the exoticism, but it sounds like that's not the case. If I can get a chance to drive both I will do so before buying, though that's probably not all that realistic given the relative rarity of these cars, particularly the V12.

With regards to the rest of the vehicle, I'm well aware that 30 year old (and British) means a fair bit of maintenance, and honestly that appeals to me. I have a cousin who grew up restoring old MGs with his father, and I've loved British cars since I was a teenager. But I'm trying to be realistic about my own abilities and limitations, and what I can and can't handle.

 

Excellent responses here, l quite agree, generally...
I have both cars in my stable, both have their strong points; As daily drivers the 22mpg (thanks, Andy bracket) AJ16 wins out at the gas pump for sure

The smaller horsepower of the AJ16 can be ameliorated by suspension upgrades (sway bars, springs, shocks) and Pirelli P1 tyres to give the car some huevos

However.

To paraphrase Kenneth Graeme, there is *nothing* quite so much worth doing, as driving a V12 😏

Simple upgrades, not requiring engine removal or dissassembly:
A shift kit (Transco is best) will wake up the GM gearbox nicely,
A set of Webers and exhaust headers will put you firmly in the 400+ hp range, and eliminate all previous electronic injection faults

Finish it off with a 5 or 6 speed manual gearbox and you are nearing supercar status

Were l you, as a non-daily driver, l would definitely choose the V12 🥰

 

I basically agree with you about the V12; but I honestly believe that this point you made is just not true of an HE V12 engine. I am open to correction, of course.

 

Any engine modding would be limited to things that could still pass Colorado emissions, so I’d keep the car mostly stock. Stuff like advancing the timing, or opening up the intake and exhaust, is reasonable though. I’ve heard only good things about the timing bracket mod for the 6 cylinder, from looking at this forum.

Is there any meaningful difference in handling and road feel between the coupe and convertible? My wife and kids both want a convertible, and there are way more of them in the USA for 94+ cars, so that’s very likely what I’d get.

 

Dr_Awesome,

It may well be different in the US, I'm sure US members will chip in. But in the UK, Late 4.0 Coupes were fitted with Sports Suspension (Springs and Shocks), whereas 4.0 Convertibles were fitted with Touring Suspension. Owners could of course specify the option either way, but that's how they came as standard. I changed the springs and shocks on my 4.0 Convertible 12 years ago for Sports springs, Sports shocks at the front, Sports springs and adjustable shocks at the rear. But then I like the feel slightly tighter. If you're travelling with the family, you'll feel fine with the standard setup. I think the body is quite rigid in the Convertible, It has big strengthening tubes in the sill cavities and front and rear body braces underneath on late cars.

Cheers

Paul

 

Can’t think of any reason to get a 4.0, get a v12 of get another car(unless you’re plan is to swap an xjr-6 driveline)

4.0 doesn’t even rev to 6k

then again, I wouldn't have a v12 without a manual either.

whatever you decide, make sure you get one in the absolute best condition you can,

 

Paul: US spec cars are similar, we (l have a Jag shop) have never seen a 4.0 car fitted with a rear sway bar, even the body studs for fitting are absent

 

Greg in France: It's true that the pre-HE hards flow better than the late ones, but the long stroke crankshaft more than makes up for that deficiency...

Early heads married to a long stroke crank = heaven 🙄

 

On reflection....Before someone takes the leap and fits pre-HE heads to a 6.0 engine....There was only a couple years' production in which the pre-HE head was drilled and tapped for metric hardware; pre - 1980 heads do not use metric fasteners, creating something of a hermaphrodite, although no worse than a Ford four cylinder head of the same vintage (metric intake manifold hardware next to English standard exhaust manifold hardware)

 

Dr. Awesome: The most restrictive aspect of the breathing is the exhaust manifold and muffler setup, which probably cannot be changed without affecting emissions inspection

A large number of AJ16 exhaust manifolds are cracked by now, and unavailable, so aftermarket headers fulfill two functions 🤔

 

In the V12 versions, at least, the convertible handling and body stiffness is vastly worse than the coupé's. The 6s may be different, I have no direct experience of them.

 

I bow to your knowledge; but this is a bit different from saying throw some Webers and an exhaust manifold on an HE and get 400+ BHP!

 

Tks for that. Rear Anti-roll bar was not a fitment on late 4.0 cars, even when Sports suspension was fitted. When fitted, the Sports spec was limited to just different Springs & Shocks on the rear.

Cheers

Paul