I am planning to change the plugs on my XK8....i have never done this before....i have read a few posts and have a few questions:

What is the difference in the plugs...the prices seem to be all over the map? (price wise)

Can and should the coils be cleaned?

Does the cover plate require a seal?

I also read that there is sometimes oil down in the spark plug wells.....what causes this... and if I find it how best to remove it?

Will i require special tools?

Thanks in advance for your responses....I am new to the site. I find myself reading it constantly.....the information here is amazing

Thanks again

 

[quote=06aces;508711]I am planning to change the plugs on my XK8....i have never done this before....i have read a few posts and have a few questions:

What is the difference in the plugs...the prices seem to be all over the map? (price wise)

Can and should the coils be cleaned?

Does the cover plate require a seal?

I also read that there is sometimes oil down in the spark plug wells.....what causes this... and if I find it how best to remove it?

Will i require special tools?

Did mine yesterday.I used NGK PFR5G 13E - that's what the book specified.I used CRC contact cleaner on the coil connections. The seal on the cover is built in - doesn't need replacing as far as I know(someone will soon correct that if I am wrong).Use anti sieze on the plug threads and di electric grease on the ceramic and rubber boots(but not too much). Don't turn reinstalling the plugs into a show of strength - alloy head- use a torque wrench. If the spark plug wells show oil then the seals are leaking and you need to take off the valve covers to replace.

 

This is an easy job. The plug prices will be all over the map just get the right plug for the best price. I think the plug is listed in your owners manual.

Oil in the well means, usually that the seal on the valvue cover has let go. So you now will need to replace the valve cover gaskets. Before you tak any thing else off I would use something to blow any and all debris out of the plug wells. If there is oil in there What I have done to mine was to soak it all up with bounty paper towels, The quicker picker upper! in this case they are.

I rolled the ends narrow and fed the towel down the well the I used a long skinny screwdriver to pack the towel to begin soaking the oil. But do not over pack so you have to now fish out oil and paper towel remnants. Remember you are just soaking up oil.

The biggest issue I have had was to get the bolt out right on the lower left(passenger) and lower right (driver) on the valve cover. I ended up using a 10mm swivel socket. The other issue is the oil dip stick tube. Just try not to pull it totally out just move it enough to clear the stud.

This is not hard it just takes a little time.

 

The car has platinum or iridium plugs from the factory that are rated for 100K miles. They really can last that long unless they were fouled for some reason. These generally run in the $10-$12 neighborhood apiece.

 

Here's the various specs:

Spark Plug
NGK PFR5G 11E : Normally Aspirated
NGK PFR6G 13E : Supercharged

Plug Gap
0.039 - 0.043 : Normally Aspirated
0.047 - 0.051 : Supercharged

Torque
25 - 29 Nm : Spark Plug
4 - 6 Nm : Coil
4 - 6 Nm : Cover

With torque settings, the lower figure is for previously used fittings, the higher one is for new. New plugs therefore go to 29 Nm but used Coil and Cover bolts go to 4 Nm.

If the seals need replacing, there's a US vehicle has the same set at much lower cost than Jaguar parts. I think it's the Lincoln LS. Others will be able to confirm.

I'm not a fan of dielectric grease and prefer clean contacts but that's just opinion and you'll find as many for using it as you will against.

Graham

 

If the seals need replacing, there's a US vehicle has the same set at much lower cost than Jaguar parts. I think it's the Lincoln LS. Others will be able to confirm.

It's a Felpro gasket set - part number is VS50724R

 

Have your secondary tensioners been updated?

If you have the valve cover off to replace the seals (if you have oil in the spark plug wells) that is the perfect opportunity to check your secondary tensioners and update them to the metal type if you still have the original factory plastic ones.

 

The 1.3mm gap plugs can be used in ALL 4.0 engines.

TSB 303-29

bob gauff

 

wow....these responses are great......thanks to all

 

Dont ignore the gap - it is important! Good Luck, it is easy.

 

Here an overview of plugs and gapping from Jaguar:

 

Avos: I used the info in this document and set the Gap at .035 to .039 inch when I recently replaced my Plugs.

Since this Information was published more recently than TSB 303-29, I assumed that the reduced Gap should be used.

 

When I changed mine the NGK box advised "Do not adjust spark plug gap due to possible damage to fine center electrode" ?????

 

Correct, the TSB is only for the AJ26 engines (as it was made in that time), they have different ignition parts and timing as AJ27 ones, whch may explain why Jaguar still wants a different gap between the 2 engines.

 

You need to be very carefull, although iridium is very strong it is also very brittle, so the fine tip could be damaged if not carefull. For the AJ27 engines I wouldn't gap as mentioned.

 

Any plug can be gapped or re-gapped; one must be careful how it is done. Using the proper tool to bend the curved electrode (yes, there are tools for that) is the correct way to change gap, as this does not involve touching the brittle iridium electrode in any way.

Also, just to throw this additional (and confusing) information in, the specifications for spark gap listed in my Driver's Guide Book (published date--July 1999 for 2000 XK8) shows electrode gap of 1.0 - 1.1mm (0.040 - 0.043 inches) for both normally-aspirated and supercharged engines using unleaded fuel, both using NGK BKR5E-11 plugs.

As of this date (9-2016) those exact NGK plugs are not so easy to come by; I cannot find a local seller. So I went to NGK's website and found that they no longer list those exact plugs, but, for my 2000 XK8, showed three different compatible plugs: the Economy plug, the Iridium plug, and SuperDuperKrypton somethingwhoknows plug--from cheapest to most expensive. The site warned that the Economy plug may not fulfill specs for my car, while the other two more expensive plugs exceeded the specs (since this is the Jag-recommended brand of plug, and NGK says that they exceed the specs needed for my car, and the original plug, that was good enough for me).

I bought 8 of the 'middle-cost' iridium plugs, and, while more expensive than the economy plugs, were quite a bit cheaper than the most expensive. The part number was BKR5EIX-11 (5464). I was able to acquire these at my local AutoZone for $55.92 (set of 8, pre-gapped--although I checked the gap just to make sure).

 

So my local parts store said the 11E is no longer made and they offered me the same number without the 'E". Is that the correct plug now?
Thanks
Alan

 

According to the manufacturer NGK website NGK PFR5G-11E has been superseded by NGK PFR5G-11.

My seach also found an interesting decode for plug numbering system:




Graham