Hi, I'm almost afraid to ask this one, but here goes. I just changed the plugs on my 1998 XK8. Use Irridum, 0.052 gap. Wow, nice difference. Side bar, but based on what I found I would never ever wait 100K miles, my car has 71K, huge improvment. Smoother faster start, nothing but positive.

But that's not the reason for my post. 6 of the 8 plugs had oil on them. The oil was definitly present above the plugs threads, in the cavity that surrounds the ignition coil lead. When I took the coil out the very tip of the rubber tube was wet with oil. Only 1 or 2 of the rubber tubes had oil along its side. I can't tell if the oil I see on the plug's threads or just below the threads was deposited during the removal or not. None of the electrodes had any oil.

I wanted to ask you what you think may cause this, what I shoud watch out for? There is absolutely no extraordinary oil consumption.

Here's one that's way out there, but let me ask. If during it's previous owners' life, he went through a "Cylinder wash" no start issue, then had a mechanic follow the "cure" and insert oil into the cylinder, could that/would that leave a deposit like I just described?

Thank God she is running strong, but I didn't exepect this and wanted to ask. Thanks for your thoughts.

 

This is a regular issue. It's unlikely to be anything more serious than leaking rubber Spark Plug Boss Seals. See item 3:




Early cars have separate seals; later ones have them combined in pairs with the centre seal as a single moulding (see item 16)

To replace the Spark Plug Boss Seals, you will have to remove the Camshaft Covers so you will need a full seal kit. USA members will be able to advise where to find Ford alternatives to buying OE Jaguar.

Graham

 

Later cars have the separate seals.

 

+1

 

Correct.

Early 4.0 Litre models were fitted with NCA2578BB paired seals. Later 4.0 Litre models were fitted with NCE2578BB individual seals.


(click on the image to enlarge it)


4.2 Litre models were fitted with individual seals commencing with AJ82876 to VIN A33834 but this P/N was superseded 5 times throughout the production run.


(click on the image to enlarge it)

I haven't seen as many examples of 4.2 Litre models as these appear less prone to seal failure but I'd expect the design has remained as individual throughout.

Graham

 

I wanted to say thank you to each of you who took the time to respond. This sure is a relief - thanks again.

John

 

That's unusual. Most owners report that their plugs are still going strong at 100K+ miles and wonder why they bothered changing them. Owners who don't change them until the engine no longer runs report 400K+ miles in some cases.

Would you have a picture of the electrode end of your plugs?

 

Hi Mikey, Sure I saved them, but we are in a blizzard up here so it may take a little longer than normal.

These are in terrible shape (electrode) quite corroded looking. Check back tomorrow and let's see what you think.

 

If the fouled plugs were on the US drivers side, it could be a simple as a spill from the oil changes getting past the seal on the coil covers. You also find coolant on the two plugs closest the the firewall next to the reservoir.

 

gap was aboutt 0.044.


Mikey, photo as promised. Hope it helps.

 

I just changed mine out last month, original NGK Iridiums at 131k mi. btw, and also had a bit of oil around all of them. I only changed them as I got a CEL for a misfire on one of them and this cleared the issue. Not only a bit of oil, but the plug tops were coated in what appeared to be rust- the surface was just highly deteriorated at the least, nothing flaking off. Electrodes looked perfect. Runs just as well if not better now.

 

I've run iridium plugs (Denso) on a couple of my wife's previous Lexus SUVs to more than 130,000 miles with zero issues and no discernable wear when I changed them primarily to get the vehicles ready to sell. As long as the vehicle's seals hold up and keep them relatively clean, iridium plugs can potentially last 250,000 miles or more....

 

I have a (new to me) 2000 XK8 that I am going thru revitalization after several years of storage. I pulled the spark plugs today and was surprised that they basically look new other than light carbon around the base of the threads. I had already purchased a set of new NGK Iridiums so I'll replace them anyway. According to PO and records the plugs have not been replaced. Car has 95,000 miles. My question is: The left bank plugs all have bright white insulators, and the right bank are all very very light tan. I am used to seeing some color on the insulator. Is this lack of color normal ? There is no evidence of overtemperature or blistering. Using a scope to look at the top of the pistons there is a light coating of carbon and you can still see the triangle (or is it an "A" ?) clearly, and again no indication of overtemperature. Oh, and the spark plug "bores" all had a ring of oil as stated above, putting new seals in when I replace the cam chain tensioners of course.

 

Hi 64vette,

This is a great question, I'm afraid I don't know the answer. Since I was the guy who posted the original question back in January I took the time to scroll to your new post.

I am worried that you may be waiting longer than you might like since this is burried under a thread that has a completely different subject. You may want to just copy your question to a new thread with a subject like - half the plugs are yellow - what does this mean?...

This may get you some prompt attention from someone who knows. Hope this helps mate.

John

 

I don't know if the 2000 uses iridium...

(the later do, i.e. 4.2, I'm fairly certain)

 

How difficult is it to replace the seals? Are there any documents on a procedure here on the forum? Thanks in advance...

 

My 97 xk8 that I drove for 9 years had oil on the plugs, same as you. I replaced the seals(easy), and problem went away for about a year. Then it happened again, more oil in the plugs. Maybe it's because I used aftermarket seals? Who knows.. It never affected how the car drove, very smooth. I just left if like that, never had any problems

 

First you may consider adding your year/model in your signature so we can tell what's what.

See the post above from Graham on pics of what's involved. Also it would give you a chance to check your tensioners if you have a pre 02 model. Look/search under Tensioner Replacement as it'll provide directions on how to remove cam covers.

 

I've got a 97 xk8 and the spark plugs are up to the contact at the top of the plug with oil. The ignition coil rubber tubes are filled with oil. I've had two ignition coils go out and I suspect the oil isn't helping. So, going to need to change out the seals. What is a good source for the seals here in the US? How difficult is it to change out the seals? Also, I don't know what gasket/seals to get. I'm confused; reading about AJ26 and AJ27. Need to know what to get.
Thank you in advance...

 

Skubeedoo i think someone posted about this a week ago (ish). I never did anything to mine so I can't help more. John