Hey, I dont usually post in depth things on the internet. I find forums can be a very toxic place, some people would start an argument with them selves. I don't want this being one of them please.
However I though there might be some genuinely interested partys that might like to see some pictures along with progress reports over the next few weeks.
Two weeks ago my 2008 4.2 XK was over heating. That was down to the water pump which was easy enough.
So after two days of driving the car suddenly gave an over heating warning light on the dash. I was maybe a mile or so from my home, so I drove slowly and the light went of. The engine was running great, no noises ....nothing. Then once on my drive the engine just stopped....nothing. It would not re start so I thought I would let it cool down over night before I investigated. The next morning the car struggled to start and when it did it sounded like half the cylinders were running. Strange because the engine sounded great up to the point of when it stopped.
Next day, I did a compression test and on both cylinder heads the last two cylinders were not registering. Mmm, two blown head gaskets maybe.
Started stripping it down and eventually rook the left head of, dam. Valve seat pushed out and has chewed the material around were it sits. Some thing tells me inside that the right head will be the same. It is.....in fact it's worse
Guys and girls, I will keep you updated and pictures posted for your entertainment.

 

....

 

Beyond my skill level there, I hope you can fix it.
Question: Your coolant looks green, is it the correct type? I’ve only seen orange/pink in these cars.

 

Interesting as I have never seen seats pushed out like that. Assume the overheat and the material difference between the head and seats contributed to it. Looks like one of them ruined the head. Can the heads be rebuilt or are they toast. Good luck and keep us posted. I burned a valve in my V12 and pulled that apart and salvaged the head . At my age now I don't think I would tackle your job.

 

This is quite common on the 4.2 engine. Normally after 70k or so. Hate it happened again.

 

hey, yes I used some coolant i had laying around until the job with the change of water pump was good.

 

I have removed the valves and to my surprise the valves/ collects and guides are untouched.
Even the seats and cut outs them selves are not damaged, just a bit of damage in the surrounding area, not much it seems.
So they might be able to be saved and have new seats pressed in. Notice how one seat is half in half out😳
I have made inquiries about a few heads if I need them, but after seeing the head stripped. They might be saved 🤔
Thank you for your interest.

 

Agree with your sentiment on forums and arguments, however reading through this one it doesn't seem to be the case, just a lot of interesting technical discussion and support - I've already learned a lot. Watching your thread with interest, please keep the information coming.
Quick question - did you need to take the front bumper or even the nose off to remove the head? Or did you just want better access - having done the same twice its quite an involved job - just finished putting mine all back together as I type this (pedestrian sensors change)

 

Love these types of posts. No one here is going to start a fight. Not many DIYer's in this forum but that will change as these cars get older so please add as much detail, steps and pics as you're inclined to do. This thread may very well become a how to and land in the sticky section. Thanks for posting this

 

Hey, regarding taking the front out. I have done a lot of work italian exotics I own, and I find that especially on front engine cars, the more room the better.
I am really glad I did remove the front on the XK. For such a big car the access to the sides of the engine is as tight as i have ever seen on a car. Talk about over engineering, and my son is a precision engineer 😳
I was especially glad I made room to get to the front pulley which is better removed head on, also sitting in front of the actual engine is fantastic.

 

SBS,
Compliments on your methodical approach to things. Especially appreciate that you are taking the time and trouble to post the process here.
- I'll be interested in learning more about the dropped valve seats, and whether the block and heads remained square and flat
- Any piston/valve impacts?
- Was all the in-cylinder coolant due to overheat (or did you simply choose to not drain the block before pulling the left head?)
- Any idea what triggered the subsequent (most recent) overheating episode?

 

No experience with this type of issue and repair, so pardon question out of ignorance... seeing how the area around where sleeves/valves inserted is damaged, wouldn't that create issue with valves sealing even if you put new seats in?

 

no, there just burns and can easily be sanded down. The valve seat insertion area is untouched. Skimming and inserting new seats this week. May use slightly over sized seats.

 

That is really good to know thank you.
2 things you should consider doing while you have it all stripped:
1. Change the aircon condensor for a pattern one (they are made of cheese and it will fail if JLR standard issue, any time now). £200 pattern part lasts far longer. Be sure to get the right o ring (one is £17)

2. Change the Pedestrian sensor unless you have the grey one in my pic. The blue ones are made of chocolate and last as little as 50,000 miles. £93 each. You need to drill a hole in the back of the bumper to take the locating lug (6mm I think)

My stuff was bought from SNG Barrett

 

l
No valve to piston contact, just light crown scoring from the valve seat. Nothing to be concerned about. I expected way more damage to the valve, colletts and guides, but none. The valves did not do down any more than standard due to the colletts staying intact.
Regarding draining the block of coolant, I did not bother with that, I needed to just get into the engine, a little coolant spilling is not worth bothering with......bigger fish to fry 🤗
Now the cause, as i said i did change the water pump due to it being loose (made a video of it).
However i did also find a hose that had burst.

 

I'm confused - did you have green coolant in there the whole time? Or just after you replaced the waterpump? Was the waterpump and burst hose the root cause of the original overheating?

The green coolant is incorrect for this engine. There's even a sticker on the expansion tank that shows only orange should be used. Not sure if that would cause overheat but I would definitely flush out all the green stuff before you get it back on the road.

 

Dont be confused, go back and re read post 6.
I know about what's the correct coolant and what's not. That bit of green coolant in for a day or so will not cause what you see in the damaged engine.
But being that you are giving advice, any advice on how to rebuild the engine? 😂😂

 

Thanks for the pictures and detailed post. I've read about dropped valve seats in 12 cylinder XJS models I was interested in buying one that hadn't been run in years. After we got it started up it clattered like an old truck. Thanks for the view inside the cylinders. Good luck with your project.

 

SBS, not advice to offer and llease be reassured there won't be any wars going on on this thread. Simply as there's no contentious issues, your a member thst needs advice.

Just some question's though:

1) Does your car have full service history?
2) Anything funky done by you (e.g. larger injectors)?
3) No warnings or misfires whatsoever?

I think thst the average age of most XK owners averages out at 50something+ as such we may be an opinionated lot. And whilst some of may have had the skill (I've ported and polished a few and evsn reprofiled my own CAM's) now we'd not even attempt such things.

I wish you all the best in finding a low cost diy fix, but it certainly does sound as if your competent and diligent to see it through

 

For those who are wondering about how the cylinder heads were removed from the car, and what to do about the exhaust manifolds. Dont even try to remove the exhaust manifolds, you cant. It's far more simpler to just undo the two nuts that hold the catalyst to the manifold. Do this from under the car.
The manifolds are quite streamlined and taking/lifting them out along with the cylinder heads is very easy.