Panic reporting - valves expert opinion needed : sudden zero compression on cylinder 2, XJ6 1985

What Paul said; I would be worried about more valves sticking due to the sludge which I have no explanation for, but if the valve can be closed and still has compression I would clean off as much as possible and then take it on a long! run, and only shut the engine off upon return.
It’s not too pessimistic to assume that the valve is bent though so I would buy a head gasket, valve, invest the 2-3 days and then take it for a long run… I‘ve been there when I was trying to burn off old fuel in small quantities… bent four intake valves when the stems collected the varnish, and got glued in as the engine cooled down.


It may also indicate a bent valve, Rui, possibly due to recalcitrant valve reaction - any piston/valve contact will bend the valve. Or, of course a valve seat issue…

You may of course try the remedies suggested by others, which may or may not work. But since you are prepared to remove the head; it is likely the best idea - to clean out the mess, and inspect the lot…

xj6 85 Sov Europe (UK/NZ)


Well, I would say, never do more than needed for good operation. there is a 3.6% change all will be good after a little tap.

Thank you all for the advices, much appreciated.
I spent an hour or so in the garage today.

  1. @Wiggles I can turn the tappet clockwise and anti clockwise maybe 90 degree but then it gets stuck, country to the other tappets turning freely. I can also move it up against the cam but the valve stays down, even after some tapping.

So it seems clear the head has to come out.

  1. I looked inside the cylinder again and there is no sign of impact between cylinder with anything.

  2. My car is a series 3. reading the workshop manual it seems that the inlet manifold comes out attached with the head (??? your views ? ), contrary to the carburetor model (@davidsxj6) , at least it does not say specifically to remove the inlet manifold with injectors. weird .

  3. Meanwhile the bolts between the downpipe and the exhaust manifolds are very tight, even after soaking them with WD40 for a couple of days one came out only with a long lever and the other broke :face_with_diagonal_mouth:

  4. I wonder if S3 head will come out the same way as with S1 and 2, not sure i will have place to put jacks each side as shown in (

More news as i progress, it will be slow as i do not have much time these days.

Have a good week,

One additional question, do I need the special tool indicated in the manual to adjust the chain tensioning ? Any other way to do it safely otherwise ?

No: you can adjust the chain without the special tool. On the fuel injection, yes, it comes up with the intake manifold attached. Be careful cause there are all kinds of little vacuum hoses and electrical stuff attached to it so make sure you make a map of it.

This is also a long stud engine, so when the head is off, now, is the time to replace the freeze plugs, and check for corrosion on the studs themselves.

If its not too late, I just take the exhaust mani to head nuts/studs and push the manifold out of the way.

If needed, I get them later when access is easier, and they have soaked in penetrating oil for longer, also, I would not even try one without heat, even my strong butane torch makes an incredible difference with seized fastners

I also let penetrant soak down the head studs and tap them periodically with a brass drift to mechanically vibrate any solidified bi metallic corrosion

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It’s sort of a matter of taste, Rui…

There is room enough to extract (and replace) the head with manifold(s) attached. However, it is easier to work on the bare head on the bench. If the head is off with manifolds attached there may then be some difficulties to get enough leverage to detach the manifolds. Further; there is a lot of disconnections necessary between the manifold and body…

On the other hand; getting the head loose may require some force - and the attached manifold(s) are ‘jacking’ points.

It’s only after the fact that you may regret the way you did it…:slight_smile:

xj6 85 Sov Europe (UK/NZ)

You can leave it attached, that’s easier because the nuts are so difficult to reach. If you want to you can remove it later, and then it is easier.
You could disconnect the exhaust manifold from the head! I see Tony mentioned it.

I prefer needle nose pliers to the cam tensioning tool.
Be prepared for head stud trouble if one unscrews or, worse, breaks (only if it wasn’t maintained well at some time). The engine is the same as s1/2, so it will come apart the same way.

Monday evening progress. The other two bolts on the down pipes came out relatively easy with the wrench on the photo (same used to take off the two other on Saturday)

Note how clean the oil is , maybe the black gunk on the valve train is what it is supposed to be after75000 miles ? But on my S3 e-type with 120k miles the valve train was super clean in comparison :

Question of the night: will I leave the intake manifold on, how do I apply force on that side , I have no way to fit a jack and I am not convinced the head will come off just like that . 25 years ago I restored a Fiat X1/9 and taking the head off was a nightmare, luckily I was living in Italy and the local workshop lend me a special tool, it would be impossible otherwise.


Hi Rui, I have three CARB XK engines and in each case the head has released with multiple hits from a hard rubber mallet. Have not had to apply jacks yet. Maybe just lucky. FWIW.

Thank you Paul, wish me luck !

Just make sure that if you use a jack on either side, to use a block of wood underneath between the jack and the head, with the pad of the jack centered between ports. Otherwise, you can shatter the port tract.

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The problem is corrosion between the aluminium head and steel studs, Rui - sometimes a very loving embrace. Brute force, properly applied, is sometimes the only solution - and sometimes head yields with little protest.

Attempts to unscrew the studs before the head removal usually breaks studs.

xj6 85 Sov Europe (UK/NZ)

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It should be clean. But I have seen heads as dirty as yours, not sure why, probably residue from a lack of oil changes in the past that sticks around forever?

The head will take time to come off, but it will…

No idea wrt the sludgy valve train. I have the car for 23 years now and always kept oil crystal clear. Bad maintenance in the earlier days ? Hard to believe seen the low mileage and the look-new condition. Only thing, the car is often not driven very long distances.

Question of the day how do I manually crank the engine ? It seems impossible to arrive to the crankshaft nut without a special made tool with the radiator in place. Bloody Jag engineers …

Progress of the night,:

All disconnected, radiator out for better access. Easy to crank the engine by hand like this

Studs seem ok, 3 came out however. Soaking in wd40, but they seem loose . I did not have enough PB blaster :frowning:

Problem seems to be exhaust cylinder 2 sticky valve, the stam is full of sludge while all other valves are clean .

My theory is that exhaust valve guide nr 2 had a problem for a long time . A bit of the exhaust passed through the guide and slowly built all the otherwise inexplicable sludge in the valve train . The sludge in turn accumulated also on that valve stam until it started to get stuck, mostly when cold . My theory at least .

Exhaust valve cyl 5, ok, below

Exhaust Valve on the affected cylinder NR. 2, below

Will work on it in a week time . I miss an.engine crane.

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getting the head off will be difficult without an engine crane (or some other form of lifting from above)

slim bottle jacks are excellent to get it started, then wood passed under (dont crush any valves, take the cams off in doubt)

in any case, it must come up dead straight, as soon as it becomes “cocked” on the studs, you have to knock it back down with a mallet

Thats where you will gagging for a lift, as getting them up & over the studs can require the head to be moved up & down on the studs a few times

Good luck

Good news:

Yesterday I disconnected the sprockets and the head is only standing on the block thanks to gravity, I can see i can easily move it but with the extra weight of the inlet manifold attached to it I need some kind of hoist.

Here’s my conclusion : On the S3 the head comes out together with the inlet and exhaust manifolds, they can serve as a support for belts attached to a hoist. That is coherent with the workshop manual and would work perfectly well for any car within the expected life time when the head would be free and not stuck on the studs after decades.

Now, would the head get stuck on the studs, I would like to speak to anyone who managed to remove the head without removing the engine. Again, this is the case for S3 with the injection manifolds, on the carburetor version the technique of using small bottle jacks on both sides, after carbs removed, would work well.

To be continued

It is almost inevitable that it will get ‘stuck,’ inasmuch as any differential of height, front to back or side to side eill caused the head to get bound on the studs. It most certainly can be done, but having some kind of a lift is almost a must