My XK is coming up to 100k miles and looking at the service book, that means the spark plugs are recommended to be replaced.

Anyone done this and have the steps to replace the spark plugs?

Also how many spark plugs are on the 4.2 XK (non-supercharged).

Think the part number is C2A1535



Thanks in advance.

 

Errr... since it's a V8, I'm pretty sure there's about 8 spark plugs. You need to remove the individual coils on each plug and try to clean out any debris around the plugs before removing them. Not that hard to do but try to find a spark pug socket that has an insert to hold the plug after it's loose. Otherwise it will just fall out of the socket when you try to pull it out and it's a deep hole the plugs live in.

 

Yes, long way down. Pop the vanity covers off the valve covers once the intake cover is tossed aside. Then warm the engine to full operating temps. This causes the aluminum head to relax it's grip on the plug and keeps you warm on a cool day. Pop all the coil pack clips off and lay the wires out of the way. 8mm head bolt releases the coil pack and they more or less slide out of the hole. Two of mine caught on the edge of the valve cover inside and there were bad words said before they came out. Lay them in order and inspect the plug end for burnt contacts or a swelled boot. A 5/8" spark plug socket with the little rubber hose inside will hold the plug once it's out. I used a 12" extension. Hopefully the last guy didn't over torque them. If they don't want to come out freely once over 3/4 turn loose, use your favorite stuck bolt spray and work the plug back and forth to help loosen the grip. It'll eventually come out.

Lay each one in order as they come out because it's the only way you can see what each cylinder is doing while it's running. They should all look alike. If you have any questions, post up some detailed pictures. For reassembly, first check the plug gap and set it to spec. Then get a foot of 6mm or 1/4" vacuum tubing and pop one end on the plug before putting a dollop of anti seize grease on the threads. Now, gently drop the plug in the hole, stand it upright and gently turn it counter clockwise until the threads 'click' as they mate. That's the easiest way to ensure that you don't cross thread the plugs. Then spin the hose until the plug stops turning in and pop it off the tip of the plug. Once they are all in place, use a regular 5/8" socket or remove the rubber tube from the spark plug end and torque each plug to spec. Then coils, wires and covers. I usually start the car before putting the vanity stuff on.

I forgot about the intake tract. It'll need removed once the engine is up to temp. Should take about two relaxing hours the first time.

 

Great advice for everyone to note!

As I buy my cars used... The first thing I do is replace plugs just for this reason (along with every fluid in the car).
Reading plug conditions can tell you a lot about whats going on inside that particular cylinder. I usually poke holes in a small cardboard box representing the 4 cylinders per side (and marking where front is), and press the used plug tops into the corresponding holes. (I've accidentally mix them up if I just let them float about the garage counter thinking I can keep them straight...) Now this is just habit before I start the job.


V

 

Do not use anti-seize with some plugs (e.g. NGK which I expect are the ones for your car) as the plugs have a suitable coating already.

Also, they are pre-gapped and if iridium (as I expect) do not touch the tiny electrode as they are very delicate.

BTW The rear plugs are awkward access on some of these V8s...

 

I replaced my plugs last year. There are 8 but I have had cars where there are 2 plugs per cylinder.

The Plugs are NGK Iridium. I got mine from the US from Rock Autos as they are a lot cheaper even with the PP. Item NGK7866
Jaguar will charge you around £14 each.. RockAutos charged £60 for 8 delivered to the UK.

Some of the plugs positions are a bit fiddly but a couple of different length extension bars will help and use 3/8 drive sockets. Don't overtighten them though.

 

Errr...not an unreasonable question as some V8's have twin spark engines - 2 plugs per cylinder. MB and Alfa Romero come to mind.

 

Thanks all, been a real help! Will give it a crack...

 

I've not seen this yet, but know all reciprocating aircraft engines do as well.

I recall pulling the head off a Supra once and noted the casting allowed for a second plug if they drilled and tapped it. Cool to hear there are cars that come OEM that way!

JagV8: I never trust gaps out of the box, even iridium. I'll at least verify before installing.

V

 

I was surprised as well when I first went to change the plugs on my 04 MB S430.

 

Yeah, I considered that but rashly assumed he was referring to a Jag.

 

Classy

 

No problem - but be very gentle with the iridium tip.

 

I have a 2007 XJ8 with a 4.5 L engine. The Plug is a Jaguar C2A1535.
Can anyone tell me what the Spark Plug Gap should be.

 

Didn't know there was an 4.5 liter. You mean 4.2 liter? And assume you mean XK, not XJ? Either way, both the XK and XJ 4.2 of that year have the same engine here in the U.S. Gap is 0.9 - 1.0 mm. The plugs usually come already correctly gapped though as mentioned above, some don't trust the manufacturer.

 

That's for safety reasons, they also have dual ignition systems for the same reason, whereas car manufacturers do it to increase efficiency.

 

I run a slightly cooler plugs that being the Aston vantage V8 plug

 

 

Eeek! How did I ever become a certified aircraft mechanic without knowing about dual magnetos and ignition systems?

 

there's only one magneto and it's this guy