Hi guys i've been doing up a 89 XJS tht i got in march 2014. I want to replace the spark plugs as not sure when they were last done. How difficult is it to change them?

 

depends- how familiar are you with cars in general? I don't know anything but with help from guys on this board and the write up I will link below I was able to do it. And honestly if I can do it I would think anyone can do it.

Accessing the Vee

Have a phone camera around and take a lot of pictures as you remove things so you can refer to which little spade plug went where and such.

 

and this-

Experience in a Book

 

Its not very difficult but it does take some time.

The biggest challenge is access. The front plugs are very difficult to reach unless you move the AC compressor out of the way. You do not need to disconnect the coolant lines...just remove the belt and take out the bolts. You can then move the compressor up enough to access the plugs.

It might sound like a lot of work but its not really that bad and it will save you time in the long run.

Moving the compressor will also give you more access to the "V" so you can do some cleaning and inspection.

I would suggest that you do everything while you are there..plugs, wires, distributor cap and rotor. Once you put it back together you wont have to do it again for a good while.

Mark

 

This is my take on shifting the Compressor out of the way

I hope the photo is attached, otherwise my apologies

 

Meehh, a lot of people say this is a hard job, but its not bad. Just keep everything clean.

Unbolting the ac compressor and moving it makes the front super easy, the rears near the stupid throttle pedestal are the worst ones

 

When I do mine I also take out the throttle pedestal. It adds a little time to the job but makes getting to the plugs much easier.

Mark

 

I do the same. Makes the job much easier, yes.

Cheers
DD

 

Right!

Add new fuel hoses, too. And might as well make up a new injector harness as well. And repair/replace any other brittle wires and vacuum hoses. Shoot, don't forget new throttle bushings, synchronizing the linkages, setting the throttle gaps, and cleaning the throttle bodies.

Every Jag V12 needs all these things sooner or later. Do it all, do it now, do it once.... forget about for years.

Picking away at each item alá carte is misery

Cheers
DD

 

Hi guys thanks for all your help.

I have a pretty basic knolage of car mechanics, i onece changed the plugs on my X300 but being a straight 6 it was much simpler. Does anyone have a step by step guide or better still some pictures to help. I have looked at my v12 and it looks pretty complicated

 

Changing the plugs for the first time is a rite of passage for all Jaguar HE V12 owners. Quite terrifying!

This is what I did the first time, and for that matter ever since!

• Ensure you have the correct tools. You need a top quality universal-jointed extension, a vacuum cleaner, a plug spanner with a rubber retainer so it can pull out the plug when undone, a foot length of fuel hose or similar, a 25 thou feeler gauge.
• Buy the correct plugs,
• Loosen the aircon drive belt and remove it. Undo the bolts securing the compressor and lever it upwards or forwards, so you can get to the front plugs.
• Starting at the front plugs VERY carefully vac out each plug hole which will be full of crud and grit, before you undo the plug. If you do not do this, the crud will fall into the cylinders.
• Remove each plug wire and then the plug and replace it individually, in turn, so the open plughole time is very brief and the HT lead mix-up is avoided. When removing the plug, ensure that the plug spanner is on straight. Cracking the ceramic insulator is VERY easy to do if not. Listen carefully, if you hear a ping, pop the vac nozzle over the loosened plug BEFORE you remove it, otherwise a chunk of ceramic will fall into the cylinder
• Gap the new plug to 25 thou, lightly coat the thread with copper anti-seize and poke the ceramic end of the new plug into the length of hose and use this as an extension to install it into the hole. Lightly turn it by hand until you are SURE the threads are not crossed and the plug is going in properly.
• Tighten it to JUST in, plus a VERY slight nip of about a further "5 minute" (of the clockface) turn. better to leave it loose than overtighten. A finger tight plug will function perfectly in the HE V12, believe it or not.
• Having done the front 4 or so plugs, as needed unbolt and move aside the cruise control bellows and associated stuff to give access to the next plugs along. repeat the vac procedure.
• You now come to the plugs by the dizzy and the throttle capstan. If a Lucas car, it is best to unscrew and remove the dizzy cap (three screws). BUT you also need to pull the leads off the cap. CAREFULLY label each lead with its cylinder AND make a clockface diagram of where each cylinder lead goes onto the dizzy cap. MARK the dizzy cap with where the first lead on your diagram goes.
• The you come to the plugs by the throttle capstan and at the rear. If you can get your plug spanner straight onto these plugs, they can be undone without undoing the capstan support from the bottom of the V. Undoing the capstan is a pain, but a very good plan as once undone, the plugs are easy to change. BUT the 7/8ths capstan frame fixing bolts are hard to get at, so you need to think in terms of heating and bending a spanner to undo two of them, if your 1/4 inch drive wobble extension will not get on the hex. FWIW, I believe it is a good plan to have such 'special' tools so the next time they are all ready to use.

Set aside a whole day, do not hurry it, and all will be well. Take notes of where anything you undo goes, label any wires you undo on each side of the connection; so you will not be in a muddle when putting it back.


Finally, the old plugs will be TIGHT. An 18 inch lever may be needed to loosen them, do not worry, with a CRACK they will come free!


As I said, it is a rite of passage! Good luck
Greg