New to the forum, and appreciate all who take the time to help! I am pretty active in sailing and other forums, and admire the expertise, camaraderie... And most importantly... the humor… Long time member of Roadfly, and it seems to have really gotten quiet there so I jumped at the chance to join here...

Car History
99 XK8, 60k mi
Preventative chains and tensioners job was done around 43k by me, no surprises, just a scary rattle…
50k coolant manifold failed on interstate, overheat, dropped 4 seats, complete head job was done… car ran great for the next 10k…

Crux of the matter is... I've pulled the heads on my XK8, as there was truly no other explanation for the symptoms and diagnosis other than having two blown head gaskets…The car was using water with no external leaks visible, and showing misfire codes… I personally think the car was getting hotter than the gauge let on… I’m aware of the crappy gauge resolution/reliability… Compression test revealed absolutely HORRID results… Not sure how the car even ran… 45/155/160/80 bank A, 120/30/75/85 bank B. Never did a cooling pressure test, because I thought it was going to be obvious…

What surprised me beyond belief was the fact that the gaskets themselves exhibited none of the obvious or typical failures one would expect… No clear path of failure… No “shiny clean water cylinder”. I should mention here I usually buy my parts from Pete at Coventry West, but went with a local parts guy when the heads were redone because of urgency… The head gaskets are the typical metal and composite…

Attached are 4 pics, here you can see that none of the water passageways show any sign of cylinder breach… The gaps between cylinders appear to have no gasket residue indicating possible leakage between…

What I think happened here is thermal cycling caused the gaskets to fail sealing properly… The metal substructure of the gaskets “dug into” the aluminum head pretty good… You can catch a fingernail in the dimples in the “super detail” pic…. Like the clamping force of the head was being held up by the metal “waffle” substrate, but the outer composite wasn’t sealing the cylinders… So… I think maybe I had a small water intrusion to one cylinder, explaining the h2o loss… But the majority of compression loss was between cylinders

Questions:
Anybody seen anything like this gasket failure?
Recommendations for replacement head gaskets? I’ve read about using a 4.2 on earlier 4.0???

Any other thoughts that will make me go... Ah.. Haaa... Or scratch my chin and Mmmm Hmmm... or even a simple.... Son Of a!!!! ???


Sorry for the long post!!!
Thanks Everybody!!!

 

fwiw, there seems to be a correlation between head gasket failure and the pre/post introduction of the metal shim gasket on the 4.0L engine.

there is also the fact that your heads have already been done once.

anything less than perfect preparation and execution is suspect.

for example ...

warped block deck

warped head surface

improper torquing procedure

 

I would send the head off to be checked for cracks, sometimes it could be a tiny crack that only becomes a problem once the engine is hot.

If nothing comes up there I would go ahead and start pulling pistons out looking for cracks in the cylinder liners.

But as plums said it could be from a warped block as these are aluminum it is very possible and not uncommon.

I would be very thorough to find the culprit seeing that you have already had an overheating issue once before this could have been the final blow.


When you first had the head off did you send it off to be tested for cracks?

 

Mornin' Plums... Thanks for the help!

I've done a bunch of thread post research, but apparently haven't run across the right one to give me the "ah Haaa" on the pre/post metal shim gasket.. Did read some stuff of specialty MLS gaskets, but didn't get a "don't go any other route" vibe or vendor source...

I don't purport to be "perfect", but the head installs were likely to be around #1327/8 for me if was keeping track... I've opened and closed a lot of motors, albeit less than 5 in the past 5 years...

Block was prepped well and the deck straight edged... less than 0.002"

Heads were completely gone through A-Z by a reputable shop familiar with jag-8 heads... The tech is an old school perfectionist you just don't find anymore... I had no problems for about 10k

And torquing ... I'm a tad **** there...
The only thing I would have done differently in hindsight is use new bolts instead of utilizing the "2nd use"...

pitiful.. Thanks for the reply!

Will check for cracks for sure... too much unusual stuff going on here...

Re: cracks in cylinder liners... I've read plenty about the Nikasil debacle, but never heard of a cracked liner with these engines... Does it happen? One of the common results of an overheat? (I'll do a bunch of research here)

I haven't yet dropped the straight edge on the surfaces post rip apart... Maybe I'll find a culprit....

As much as I love tearing this motor down and reassembly... The associated joy of parting with money for the required overpriced parts... AND... the lack of scalp massage motoring... I think I'm going to investigate this until a culprit is found red handed...

and yes... the heads were dye tested first go around...

 

I'm not sure it's common however I see it as a possibility that the liners could have eventually developed a crack, just due to your very low compression figures.

Did you have pressure built up in your coolant when you pulled the cap off?
I mean when after the engine has ran and cooled off was there any pressure in the cooling system? This can also come from a bad radiator cap so it is by no means a sure test just a small indication to possibility.

Measure the bore of your pistons and that might shed some light as to weather your liners have gotten simply worn out, after all you do have an early model and from what I've heard the early ones were most affected by the nikasil.

I don't know much about the nikasil so I'm no source of knowledge on that haha

Best of luck

 

Forum member 2000BlackXKR has a new company relining with nikisil. Maybe he would be a helpful source of information. He also sells new head bolts, and maybe could help on gasket information.

 

I'll take a good look at the bores and do some measurements... I have all the equipment, so why not right???

No on the reservoir pressure... I was adding about a cup of H2O every time I drove her once every week or sometimes two weeks... Not a daily driver... Don't recall pressure idling before warm due to compression losses, passed the sniff test too... No water in the oil, pan, or valve covers...

Thanks for the help bud... We'll get her sorted together and increase the knowledge base here at the same time...

Thanks for the valuable member lead Mike!!! I'll do some 2000BlackXKR thread reading and give him a shout should I have more questions than answers!!!

 

Holy smokin' boatload of apprehensive doubt BATMAN....

Of all of the things I wish I did in life.... More analysis BEFORE I pulled this motor apart is high on the list... Yesterday was reading day on here... and I learned A LOT... Scary, as I've pulled apart hundreds upon hundreds of motors... But alas... Old dogs don't know everything...

I was NOT aware that the dreaded cylinder wash could give such low compression readings... This car fits right in the "highly likely candidate" for such an occurrence... I was frustrated with a cylinder misfire, and water loss... AND... When my diagnosis and compression readings were done it was on a cold car that sat for months... I didn't bother oiling the cylinders, as my values were so low… I’d never experienced readings coming up high enough from the values I got if it were a ring loss… I truly expected a major breach in each gasket, and even dreaded timing jump before I pulled the covers….

Now… I seriously think I had an external leak, as the pulleys and some ancillaries on the front of the engine showed some pretty excessive corrosion…. A small enough leak somewhere that it burned off…

Next step is another day on the forum… The only MAJOR concern I have right now is my cylinder bores…. There were quite a few trips to the store that started with a single cylinder misfire… And worked itself out in the 5 mile trip… I had been getting misfire code 1316 generic while this was going on, and 1230 fuel/air metering… so I thought it was intake/TB/MAP-ish problems…. Codes misfire 1/4/6 caused me to be disgusted enough to let the car sit… and then 5 months later start my diagnosis with a compression test….

In short… I’m an idiot…. I think I pulled the heads for no other reason but to spend lots of money… Oh… and possibly verify that I have a bore messed up so bad maybe I need a new engine… Pretty sad with 60k on the ticker….

Off to take a long walk… exhale… cleanse my body with the best biscuit n’ gravy breakfast on the planet… and come back and read about all things Nikasil Bores….

End of update…

 

That is horrible news.
Well I guess everyone make mistakes and there is no exception to that.

To make you feel better a few months ago I rebuilt a 2006 5.9l cummins that had ran away due to turbo failure, when I put it back in the truck it simply would not start.

This was very stressful as I had bought the truck hoping it to be a quick job then resell it.

After hours of running through all the work I had done and even swapping out the pcm thinking there is no way this truck shouldn't start.

This is where it gets very stupid, I never once thought to check the fuel return readings.

I later ran the test and found almost all of the fuel supply was being bypassed to the tank.

Turns out I ruined the pressure relief valve when I cleaned everything, so no big deal I change it WRONG! still no start.

I then think the injectors are bad (unlikely seeing that the truck did run before I tore it down)

So I start pulling them out to send them off the be tested and behold!
I am a moron, I forgot to put the injector seal on number 6 which caused the feed tube to be misaligned and therefore no fuel to the whole rail of injectors.

Install the seal and she runs like a champ, it only took me 3 weeks to get that figured out.....

So rest assured it happens to everyone.

 

Truly stupid huh??? Well... That extra $500 in parts woulda been nice for something fun... Or useful... Or.... mandatory BS living expenses...*sigh*

Your story is no exception disregarding the financial aspect... I hate to see smart guys miss silly things... But... I guess all that knowledge lets us do things like this!

Have a ton of diesel experience... It's what pushes boats around... Unfortunately we make an extremely simple system complicated sometimes...

Net net... I get to take a close look at the bores and HOPEFULLY verify that this 60k motor has a lot of good miles in her...

 

1. Now you have a great story to tell
2. You will, after redoing the top end, a fresh motor for the most part.

 

Oh I have a story all right!!!

Dummy doesn't need sidekick "Dumber" any more... I got this all myself!

Top end was completely done 10k ago... So at least I don't have to worry about the heads.... except... look for cracks!

I'm going to inspect the bores and measure everything out... I suppose this is step one... CRC dye penetrant the heads and the bores... Straightedge the decks and the heads... FIGURE OUT which head gaskets to use... Get some new head bolts and gaskets and slap her back together... Figure I'll pressure test the cooling system before I fire, and see if my leak is resolved...

This of course is if the bores and the heads are still OK... *sigh*

 

How did the bores come out? If you have gotten around to that.

 

Definitely MLS. The reason I asked the way I did was to not influence the answer.

The 2001+ 4.0L engines switched to MLS and failures are much less frequently observed on JF for those engines.

 

Thanks for checking up on me!

Not quite yet... Was out of town last week, and I'm going to do some measurements and dye checking this week....

Sounds like the MLS gasket is the way to go... Does anybody have an opinion ??? Go with Cometic, or some other source?

Of course this is moot should my bores turn out to be doo doo... Quick glance at the bores that have pistons down (flywheel still locked), they look good with cross hatching still visible, and no "obvious scuffs"

 

Most people are using the Jaguar 4.2L which is MLS. You hardly ever hear about the Cometic round these parts.

The thing to check is whether you have a AJ26 which would require confirming fit, or the AJ27 which is known to be able to use the 4.2L gasket.

I "think" the AJ26 can be identified by the use of a vacuum assisted cruise control. The throttle body has an extra can sitting on it which is absent on the AJ27 throttle body.

It also uses a different coil system.

 

4.2 MLS fitted to my AJ26 without any problems yesterday.

 

I'll take a peek, and do a bit of research... It should be easy enough for me to identify... Assuming stock MLS then... I'll give the guys at Coventry West a call... Most of my parts have come from them...

Suhweeeeeet!!!

Looks like you're all the way across the big pond... How soon can you get here???

 

First 1/4mile in ~11.8sec

 

HA!

Good one... My dad used to tell me...

"the first liar always loses"!