New (to me) 1987 XJ-S V12

Hey all, I’ve just purchased a 1987 black XJ-S, running well and I’m taking it to my mechanic this week for a check up.
I have a few issues, fuses and the dreaded speedo not working problem. But on the whole it seems sound.
I’m in the process of switching out the stereo (waiting for cables) and tackling the electrics but happy with it and just wanted to share.
This is the first Jaguar I’ve owned and the help in the forums is outstanding, thank you (I’ve been silently lapping up all of the information) .


Welcome to the forums, just to help with further questions it’s handy to know where in the world you are placed, you can modify your information and place a country flag against your name.

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It will be a work in progress like all these old cars, especially brave people like you with a V12.
Best of luck, you will receive great advice and comradery on this site, a huge resource for Jag owners.

Brave is not exactly what I want to hear… :rofl:, it makes me wonder what the hell I’m doing.
I’m already finding out just how much oil it burns through and I’ve ordered a battery charger (I guess starting a big engine takes some power).
Just simple things I’ve never had to consider with a modern car.

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How much does it burn through?

Oil leaks, okay, maybe that?

I put in a higher cranking amp battery for better cranking, which doesn’t seem to actually be needed if it starts up correctly. Maybe cycle the fuel pump on a few times before cranking will help - turn ignition key on and full pump runs a couple of seconds then shuts off … turn ignition off … turn ignition back on to cycle fuel pump again.

Charger should only be needed if: alternator isn’t charging, or use trickle charger when setting during non-use of car.

How many miles? My V12 with 61000 miles burns no oil. Make sure to run a 50W oil. 20/50 or 15/50 work fine. 10/40 is too thin.

Leaking oil, well, that’s a British car. First thing i bought was a drip pan!!! After four years of work, I’m finally drip free?!?!

Speedo not working is hopefully/probably just a bad sensor. Yours will be in left side of TH400 underneath like mine. Not horribly expensive, and easy to install on a lift or jackstands.

I haven’t noticed any oil on the driveway, and I’m not sure what was used before but I have 20/50 now and will use that in future. I have just over 80,000 miles on the clock.

I think the battery needs a boost as I’ve been using it for short journeys as I test it out and get used to it. Plus seeing if the cleaning has had an effect on the speedo or rev counter :slight_smile:

So I put an earth in and tested the car, the speedo worked, plus the cruise control. Then 10 minutes later it stopped registering :frowning: , so it was back to the elimination process.

Mine has about 125,000 miles on it, use 20W/50, no oil burning either.

“About 125,000 miles” because the it had 61,000 when I bought it, odometer stopped at 80,000, a few months later started working again, then stopped for good at 83,000. I have been mentally keeping track of mileage driven since, and my calculations puts it between those to figures.

I put 400 miles per week (2.5 hour drives at 70-80 mph of highway driving, twice per week) on it for about 11 months, which is 19,000 miles of that mileage right there.

I also used a drip pan, but I am now in the process of cleaning that leaked out oil residue off everything and solving (at least trying to) some/most of the oil leaks.

Speedometer not reading speed, or odometer not registering miles driven?

Well as Englishmen with Jags, we all know the old Joke.
If no oil is leaking under the Jag, we know it must have no oil in it.!

Just the speedo, the rev counter can be flaky too.

Just the speedometer irregularities could be, and frequently is, the speed sensor/transducer or connection to it.


I’ve had a chance to look at the car again, the speedo stopped working and the odometer stopped counting too. Maybe time to check the sensor out.