Hi Everyone - great forum


My wifes 1998 XJ-8 has a small oil leak in the right front spark plug hole. I replaced the valve cover gasket - no luck . Close inspection with the engine running shows a very small leak in the head gasket when peering down the spark plug hole with the engine running. (coil pulled). Is there a chance I may be able to retighten the head bolts and maybe get real lucky? Don't think it's using coolant, just the small oil leak that gives a engine mil code and miss. The secondary tensioners have been replaced. I can't remember - do I need to pull the cams to tighten the head bolts? I have the proper torque sequence. Just wondering if it's worth a try. It wasn't hard at all to replace the valve cover gaskets and I replaced the A drum in the transmission myself, but I've never pulled a jag head. Any help would be appreciated!! Thanks Rick Kelley 540-521-5211 cell

 

Tightening the head bolts will not affect an oil leak in the valve cover gasket. You need to remove the cover and inspect the seal around the plugs. Is the seal the figure 8 type? I think it should be for your engine, which is a AJ26. If the seals are just o rings you probably have the wrong gasket set. There is also the possibility that the cover bolts were overtightened, causing a crack in the cover.

 

No - the leak is not coming from the valve cover gasket. I replaced that gasket and torqued to spec thinking that is was the valve cover gasket leaking. Turns out that it is the head gasket leaking, I can look down the spark plug hole and just above the base of the plug which is where the head and block meet there is an oil leak, which is the head gasket, Thx

 

The spark plug is threaded into the head in the dome of the combustion chamber. That is a long way from the joint of the head and block.

 

Correct. It is leaking at the joint of the head and the block down to the plug. The joint is near the top of the plug. After running for an hour or so the whole plug has oil around it. The head gasket is leaking oil. Question is wether I can tighten the head bolts and make this stop or does the head need pulled and gasket replaced. Thx

 

RVAHA....you're are still getting it wrong ;o)
The spark plug tunnel is nowhere near the head gasket my friend.
That oil leak is coming from the figure eight gasket.
As has already been pointed out, these should have been replaced at the same time as you replaced the cam cover gasket.
The cylinder head gasket is waaay below the spark plug well.
I'll bet you either have had thr wrong plug gaskets fitted or they weren't replaced at all.
Have a closer look at the head design....no different to other engines in it's class....the only place you can see the cylinder head gasket line is at the back of the engine just above the bell housing....this is where the cyl. head gasket is....nowhere near the plug well or even the interbal cam cover gaskets.
THE LEAK IS COMING FROM THE TOP AROUND THE PLUG WELL GASKETS ;o)
eplace those figure eight gaskets properly and end of leak....nothing to do with cyl head gasket.

 

XJ8-

Thanks for the response. If I understand you correctly, the spark plug hole threads are in the head near the bottom, so the head gasket would be below that. Correct?

I did replace the figure 8 gaskets (2 per side to cover the 4 spark plug holes) as well as the large gasket for the entire cover. I figured the oil was leaking around the figure 8 gasket on the front hole. I torque to spec in sequence. Still getting a lot of oil in the hole. So I pull the plug, cleaned everything completely and started the engine. There is a little ridge in the hole around the top of the plug. This ridge is around the entire hole. I can see oil pooling on the ridge after cleaning. - But cannot see any oil leaking from the higher area in the hole which is where the valve cover gasket meets the head. It seems to be seeping in at that ridge. Maybe optical illusion?? Is there any chance there could be a slight crack in the area of the ridge?

I'll double check again, but I cant see any oil coming from the valve cover gasket area.

I may post a pic to see if that helps. Thanks so much! Rick 540-521-5211

 

I thought about a crack in the head, but there wouldn't be a oil gallery in the head near the plug. It seems unlikely that the gallery to the tensioner could be the source, but strange things do happen.

 

Yeah, post some pics. This is very mysterious.

 

Rvaha.....these heada are not known for experiencing such cracks....and i still think you are wide of the mark.
There are only two 'probables' here as to how oil can get into the plug well.
The most common is of course leaking fig.8 seals or singular well seals.
Second and not very often, if at all, is oil seeping down the outside of the plug well tube and entering at the base.

The only accurate way od determing oil ingress is to fully wash out oil in plug well with carb cleaner followed by dryng with a rag wrapped round a small stick or screw driver or use an air blast.
Of course, you have the cam covers in place.

Replace plug and fit a remote lead to the coil so it still attaches to plug but allows you to see down the well with bright torch.
Set engine revs at 2000rpm for around 10 mins.
While looking down the well, you will be able to see whether oil is coming in from above or, is seeping in from below.
And my gues is that the oil will be coming from the plug well seals in the cam cover.

Early 'Fig.8' seals were fitted on AJ26 engines untill around Sep.98 when the AJ27 was introduced using singular round seals and these have different profiles.
So, make sure you have the right type of seal fitted.

The plug well steel tubes are tightly press fitted into the head and I have never seen one of these leak at the base.....not saying it can't happen, it's just very remote.

As a matter of interest, what mileage has this engine covered and has it ever experienced any 'over heat' situations?
If it has in it's past, this could have some bearing on the tightness of fit of the tubes or otherwise.

 

Pull the cam cover completely off. Turn it over and examine where the spark plug gaskets seat in the groove for each of the four spark plug holes. Compare each of the spark plug hole gaskets grooves on the cover. If the cover has been overtightened at any time, a piece or pieces of the groove may have broken off. I had a similar leak and had to buy a used cam cover before I could stop my leak.


Plastic may be light, but it doesn't like heat and becomes brittle.

 

I'll pull the cam cover and give it a thorough check again. XJay8 - it seems likely that your option #2 may be the culprit. Maybe where they are pressed in an meet the head is this the ridge I am talking about??

I had cleaned with carb cleanere and gotten the hole cleaned entirely before. This helped me diagnose the leak - maybe where the steel tube is pressed in at the bottom.

Mileage is around 125 k. It did get hot a few years ago when the water pump went out. Maybe it's just now showing up??

I'll get back to it in a few days. I did have some oil in the back hole before. This has cleared since the valve gasket replaced. The oil in the front hole is a large amount - maybe covering much of the plug after an hour or so of running.

Thanks again guys!! Rick 540-521-5211

 

I would go for a crack in the valve cover as well, I have had that a couple of times.....

You couldn't see one of them and only became apparent once the cover was tightened down

 

Guys, again thank for the responses. Hope to take a look at it again this weekend. XJAY8, you mentioned the 2 probables. If the steel tube is leaking near the plug where it is pressed in, would the leak still be coming from the valve cover figure 8 gaskets from above and would be leaking down the outside of the tube, and then back inside the tube near the plug? Or, would the oil be leaking from the head into the bottom of the tube? I'll look again very closely. thx Rick 540-521-5211

 

It will be hard to see. As you remove the coil, the boot will smear oil on the side wall of the tube unless you withdraw the coil without touching the side of the tube. If it is the cam cover, oil will seep from between the cam cover and the top of the head where the gasket seats, run down the inside of the tube and pool around the spark plug.

 

As I have said before....it is highly unlikely to be a head gasket oil leak problem
You most likely suspect is the cam cover itself or the 'figue 8' gaskets.
And as i have also said, unless this engine has suffered severe overheating at some point, it won't be the tube/head interface.
New gaskets and possibly replacement cam cover will fix it. ;o))

 

Guys, I've checked again. Pulled the cam covers. Gaskets are new and in place. Retorqued the cover to correct spec
The tubes are all aluminum and are part of the cast head. There are no steel tubes. Checked with a magnet and everything in the tube is aluminum except the tip of the plug.

I bought a remote monitor with 3 foot extension to peer into the hole. There is no oil coming from the top, but there is a tiny pin hole in the tube near the top of the plug. I can see the oil bubbling a little, esp when revving the engine a bit.

Maybe this is a casting flaw? I think the other side would be in the vicinity of the valve.

So, how should I fix? Did some heads not have steel tubes? Any chance these were removed and need to be installed? My guess is head did not have steel tube liners. Is there a chance it could be welded with the head on? The pinhole is a couple of inches from the top of the opening.

Or, am I completely missing something??? I took some pics of the monitor display. They are not very clear. Again, many thanks for everyone's thoughts. Rick. 540-521-5211

 

Well rvaha....you have me there ;o]
Can't honestly say that I have noticed whether they are steel or alloy....I just assumed that they were.
If that is the case, I would be looking at a tube of Liquid Metal or similar to
repair.
Get it a scrupulously clean as you can with carb cleaner, followed by paint thinners or methylated spirits.
This 'flaw' is obviuosly not very large so, should be relatively easy to fix.

 

I was thinking of the liquid metal type of repair as well. Problem is the pinhole is in the upper side of the tube which is very hard to see. Also the hole is close to 3 inches from the top, so the cleaning and prep work will be hard to do with my fingers. An aluminum weld would be nice, but not sure the welder would have access. Anyway, I think we are on the right path. Thanks for everyone's thoughts and a very Happy New Year!

 

That is unusual. I've heard of guys using something called JB Weld to fix all sorts of things metal. I can't say from experience, but it might be worth a try.