'95 XJS 4.0 AJ16 / I changed plugs to Champion Coppers the other day and found cylinders 2-5 dripping with oil. The valve cover gasket is dry. I assume the plugs have individual rubber gaskets around their ports? I could see where the oil was seeping in.
This would be a new DIY job for me. Is it pretty straight forward or are there any traps to be aware of? Thanks guys!

 

No rubber on the plugs Just a taper or a washer at the base of the body. Were the plugs wet near the electrode or is the oil on top of the head? If the electrodes are wet wit oil its time to do a compression test.

 

Are you certain? Looking down the port where the plugs screw in, I see oil leaking in well above the plug. This is where the valve cover attaches. I note that "Spark plug seals" are sold in 6 packs for my particular model.

 

YES! they do look it is part number15 and yes they can become dislodged and give you this result...

Cylinder Head Components-4.0 Litre-Aj6 - Parts For XJS from (V)179737 to (V)226645 | Jaguar Heritage Parts UK

you might need to redo all the gaskets of the cover 6 #15s and 1 # 14

this will solve that...

 

one pack then... get the valve cove seal too...

 

That's it then. Thanks for that handy diagram as well Jonathan!!!

 

Ok just so I don't feel real dumb the seals in question are part of the valve cover sealing process? Not the spark plug per se ?

 

Yes Sir. They are refered to as "Spark Plug Seals" in most catalogs. They are not a part of the actual plug but keep oil out of the plug"s "living space". Sorry if I misled.

 

Yeap,

that is right... when they become dislodged.... oil leaks and fills the plug well with oil... which can cook into a carbon based goo that conducts spark away from the plug... oil it self does not conduct...

 

Not to worry it is all good I try to learn a little bit every day. So far I have been lucky enough to miss the carbon based goo.

 

Jimbeaux,

The diagram and parts reference earlier in this thread is NOT the right seal for your AJ16 engine.

You need part number NBC2579AA for an AJ16 engine. See here:

Camshaft Cover - Parts For XJS from (V)179737 to (V)226645 | Jaguar Heritage Parts UK

Paul

 

Thank you very much for that! I was ordering them from Coventry West but will also check the site you linked; they are new to me. Again, thank you.

 

The intermittent rough idle I always detected vanished for a while after changing to Champion copper plugs and cleaning my EGR. It returned shortly thereafter but not as noticable. I did not do as good a cleaning as I might have on the EGR as I thought I was about to replace it. QUESTION: Is the intermittent rough idle more likely to be caused by the oil in the plug ports or the EGR?

 

Jimbeaux,

The site I "suggested" is Jaguar!

Order the parts through your local Jaguar Dealer for collection and no shipping charges to US.

Paul

 

Sorry for the slow uptake, I didn't look closely enough. I assumed they were an aftermarketer.

 

Sounds like you don't have too much experience, so let me tell you in case anyone else hasn't. Do NOT overtighten that valve cover. If you don't own a torque wrench, buy one for 15 dollasr at harbor freight.

If you can't get one, tighten until snug and check after. If you over-tighten a valve cover gasket with a "grunt" method or otherwise, the seal WILL fail and you are back at square one.

Don't know the AJ16 specs but generally we are talking 8-12 ft/lbs, overtightening will flex the cover and cause it to be loose in some places and overcompressed in others. Which causes leaks and sometimes even damages the new seals.

 

Just went through this with my 95 XJS with the AJ16 engine. I replaced the cam cover gasket and over torqued the cam cover bolts. A couple of months later I went to check my spark plugs and noticed my plug wells were full of oil. I ordered a new gasket and a set of the oil seals. There is a TSB, 12-60, that covers camshaft cover oil leaks and provides a revised torque spec. After the bolts are set to finger tight, torque to 5 ft lbs. I would recommend pulling up this TSB since it illustrates the bolt torque sequence. At the recommendation of one of the other members I also used PERMATEX fuel resistant Gasket Dressing and Sealant when installing the gasket and plug seals. This was about 3 months ago, I have zero leakage. Hope this helps.

 

I had heard that, thanks for the reminder. I am experienced with changing valve cover gaskets but not on an XJS. I will be "torque careful".

 

Thanks for the input. I will handle up on this chore next weekend.

 

You do not have them on your V12 TKD,. The oil and goo comes from other plentiful sources on the V12!

Greg