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XJ6 & XJ12 Series I, II & III 1968-1992

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Old 10-21-2011, 06:57 AM
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Default Head gasket replacement

Hello All,

I am about to start the process to replace a head gasket on my '86 Sovereign.

Interested to hear other people's experiences and suggestions.

During the process I am sure that I should be looking to service other components not directly related to the issue. What parts should I make sure that I replace, regardless. What items should be serviced seeing as how the head will be coming off? Timing chain ? valves?

Only ever worked on small (MG) 4 cylinder overhead valve models... what surprises can I expect from the XK engine?

Rhys
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Old 10-21-2011, 07:59 AM
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Corrosion between the studs and the cylinder head usually makes head removal very difficult. Bottle jacks under the ledge of the cylinder head can be used to push the head off the studs...but patience is required.

Removing the studs makes the job easier by a magnitude of about 100.....but *if* a stud breaks you'll have a major problem on your hands.

The same corrosion problem effectively welds the inlet manifold to the cylinder head. Bottle jacks are useful here as well.

You'll want a shop manual (or a helper with DOHC experience) to deal with removing the chains and gears from the camshaft. And never set the cylinder head down on the flat side...you'll bend the valves.

With the head removed you'll have lots of working room to tend to hoses (fuel, vacuum, coolnat) and repair brittle wires and dirty/loose electrical connectors. Access to the belts, water pump, and fan clutch is also much easier so any "iffy" parts should be replaced.

If the budget allows I'd send the head out for a valve grind, valve guides and seals, and resurfacing.

Cheers
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Old 10-21-2011, 07:48 PM
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Thanks Doug,

I have a workshop manual, one for a series 3 with "an Australian" supplement. Not sure if it is exactly the model that I have , but close enough given all the tweaks and changes over the model lifespan.

Happy to send out the head for inspections and valve work, but have read a number of posts where replacing studs was expected, whether they were corroded or not. I was planning to leave them untouched if possible. Sounds like breaking the joint between engine and head may be quite a challenge... other than bottle jacks, which sounds very tricky, can you use the engine compression (turning over by hand naturally) or does this upset the timing?
Reading, it sounds like any rotation of the engine, during the dismantling process, is to be avoided at all costs!

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Old 11-19-2011, 06:45 AM
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Finally got started on the task of replacing the head gasket.

I have managed to disassemble the exhaust side (manifolds etc.) with no problems. I have removed aircleaner, air meter, rocker covers etc. and am now up to the inlet side.

It looks daunting, so any suggestions about how to disassemble this side of the engine would be appreciated. I am taking photos and keeping notes, but the more components I can keep whole, the happier I will be. At this stage, I am now removing the wiring harness from the electronic fuel injection...... hope I am on the right track.

At least I can see (and smell) the polluted oil inside the engine and hope that all that is failing is the head gasket.

Any suggestions would be most welcome.

Rhys
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Old 11-19-2011, 04:05 PM
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As an '86, your engine should have the vertically machined coolant slots between the bores and NO cylinder liners, rather than the earlier horizantally machined coolant cross-passages, with cylinder liners to cover them, (as I had). So cracking between the bores should not be a problem. The paragraph below is for engines where you haven't much knowledge of the level of care and diligence of previous owners in maintaining the correct coolant in the engine. OK, you're in Australia, so anti-freeze is not necessary, but anti-corrosion additives ARE necessary.

The later XK 4.2 engines from the 70s onward have the long head studs (about 12 "), passing through the top deck through the cooland jacket to tapped holes at the bottom of the jacket. Engine numbers have 7L or 8L in them. These studs can corrode badly where they sit in the coolant, and it can be very dodgy extracting them, but extract you must to check them. So you need to take out each core plug opposite each stud to make sure that, as you extract it, it turns at the bottom, and doesn't snap off half-way down, leaving you with a mega-problem - how to get the stub out !!

FWIW, my engine had several corroded studs, but none at danger level, (of snapping). I replaced them all, I also had to make up a tool to clear out the tapped housings, as dirt getting in there stops the new stud from going in fully, then when you put the head back on and tighten down the head nuts they bind on the end of the thread, and you get a false torque figure and the head gasket immediately blows again.

Incidentally, I think I lifted my head using webbing lift slings through the cam-shaft bearing cap holes, having taken the cams out. You need two slings and put them through two cap holes per side (inlet and exhaust), put some lift on, and tap and bang away, and it should free up. This may be frowned upon by other experts, but it worked for me. Of course you need a chain block and an overhead securing in your garage.

By the way, there is no need to take off the inlet manifold to lift the head, it is a PITA to take off on the EFI engines.
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Old 11-19-2011, 04:42 PM
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Thanks Fraser,

I had hoped to leave the inlet manifold on. Once I have manage to free the head, I assume that the manifold will be strong enough for someone to lift / carry the head on that side whilst I carry the other?

I had really hoped to avoid removing the studs, but sounds as though I am better to have broken one in the process of removing than to have one break during re-assembly. Whilst my engine has only done 130,000 km, it is still 25+ years old and, from the look of the coolant, contains rust particles.

"So you need to take out each core plug opposite each stud to make sure that, as you extract it, it turns at the bottom" ....

Does each stud have a core plug? What for the ones that don't? Just extra care and hope?

Any trick to removing the studs? I intend to use two nuts, screwed down the stud as far as possible, then "locked" against each other to undo the stud. Otherwise it would appear to be "vice grips" at the base of the stud and, possibly, steel scrapings everywhere.

I presume that replacement (new) studs are available, and hopefully don't need to manufacture my own.

Again, Fraser, thanks for the response.

Rhys
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Old 11-20-2011, 04:29 PM
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Hi Rhys

It is a long time since I did my 4.2 engine, (like 1990 !!). Yes your assistant can lift on one side using the inlet manifold, and you on the other with a couple of hammer handles in the exhaust ports. I was lucky, I had lifting gear, in fact I still have the chain block and tackle in a dark corner of the garage.

Not all the studs are long, so if there is no core plug opposite, it will be one of the short ones; these screw into the top of the block, the two are the rear of the engine come to mind. At the front there are six smaller diameter studs around the timing chain passages.

You really need to buy the workshop manual and parts manuals. These are still available on the internet, are about 1" thick books, and mines of information written by blokes who knew what they were talking about.

Classic Jaguar, Jaguar XJ Series 3 Workshop Manual XJ Series 3 6 & 12 CYL. (AKM9006*) | JustJagsUK.com

and

Classic Jaguar, Jaguar XJ Series 3 Jaguar XJ6 & Daimler Sovereign Series 3 Parts Catalogue (RTC9885CF) | JustJagsUK.com

Have a read of this too, but don't get too despondent at the problems there might be -

XK Cylinder Head Problems

As for removing the studs, I removed mine after I had lifted off the head, using a stud extractor that fitted on a 1/2" driver socket wrench, as I had decided to replace them with new. YOur method is the other and traditional way of removal. I was doing a full rebuild around an uncracked block so did not even think about reusing them, but I could have reused about half of them in fact. Whilst the core plugs were out, I took the opportunity, (before I extracted the studs), to flush out the block water jacket with a hose. I took out the small studs and back jacket cover at rear of the block. This is where most of the crud accumulates, as you will find out if you flush your block out. It is due to the lack of coolant circulation so far away from the entry from the pump at the front of the block.
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Old 11-20-2011, 04:38 PM
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Excellent guidance from Fraser.

I'll only add:

If you think you *might* need to take the inlet manifold off I'd suggest doing it *now*, with the head still in place. You'll need to do lots of prying, grunting, hammering....all of which is easier if the manifold is bolted to something *stationary*....like the cylinder head in place on the engine.

Personally I use the bottle jack method on the inlet manifold as well. Just don't break it :-)

Cheers
DD
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Old 11-21-2011, 01:16 AM
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OK, thanks again Doug and Fraser,

I actually have the "Jaguar Series III Service Manual" (AKM 9006).

That is how I managed to get as far as I have! Clearly I can't be reading the right bits though, because under the section "CYLINDER HEAD - Removal and Replacement" (12.29.11) I still feel that I am doing a lot of guessing as to how things have to be done.

I have removed enough of the wiring and coil etc. off the top of the inlet manifold to at least see the nuts holding the manifold on to the head.... (why do there have to be so many?). So I am contemplating removing the manifold whilst the head is still on.... but it looks a task. I can see why others opt to leave the manifold and head intact and remove them as one unit.

Anyway, thanks again for the help and support.... whilst I am enjoying the challenge and admiring the engineering of the XK engine, I can see why my 1949 model MG was so cheap in its day! Pre-war technology and simple pushrod design!

Nevertheless, with hands all greased up, I am ready to tackle the camshaft sprockets.... just hope that I don't drop anything down inside there....!


Rhys
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Old 11-21-2011, 10:20 AM
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Quote:
Nevertheless, with hands all greased up, I am ready to tackle the camshaft sprockets.... just hope that I don't drop anything down inside there....!
Most experienced mechanics stuff a couple of rags down to catch any dropped nuts.

Taking off the camshaft sprockets is when you come across the genius of the original designer who made sure there is a bracket to bolt them up too whilst you pull of the head, and which does not disturb the cam chain and timing on the sprockets. The threaded centre of the sprocket takes a very thin nut to allow you to bolt it up loosely to the long hole in the bracket. Then, when you pull up the head, the sprockets move along the elongated hole to clear the chain passage in the head - Brilliant !!

Whilst it is not necessary to remove the cams before lifting the head, do bear in mind that one or two valves will remain open and protruding below the head-block face on the head. It is easy to forget and drop the head down onto a bench with the danger of bending a valve.

BTW, I found the Parts Manual in many ways more useful than the Workshop Manual. All the components laid out and numbered.
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Old 12-13-2011, 06:09 AM
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Hello all,

Still going... but I have a couple of questions....

I need to turn the crankshaft so that I can rotate the cam sprockets. I don't have a socket the size for the crankshaft and am off to get one. Can anyone tell me what size the crankshaft nut is?

Secondly... what do the timing marks on the camshaft sprocket actually look like. I haven't been able to rotate them yet, so the view that I have doesn't seem to show any. Exactly what am I looking for and where?

Thirdly.... The manual suggests that I use a special tool to for the chain tensioner when I finally get to removing the cam sprockets. Does the tool still exist? Is it essential or is there a work around?

Fourthly ... When it comes to re-assembly another special tool is apparently needed for timing. Some say that they made this tool themselves... where can I get a template to make my own ?

Naive questions I guess for those who have long had Jaguars... but you have to ask if you want to know!

Thanks,

Rhys
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Old 12-14-2011, 11:21 AM
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Quote:
I need to turn the crankshaft so that I can rotate the cam sprockets. I don't have a socket the size for the crankshaft and am off to get one. Can anyone tell me what size the crankshaft nut is?
It's very, very big ! I used to have one but recently gave away all my 1/2" drive sockets, so cannot tell you - Doug will know

Quote:
Secondly... what do the timing marks on the camshaft sprocket actually look like. I haven't been able to rotate them yet, so the view that I have doesn't seem to show any. Exactly what am I looking for and where?
There are no timing marks at all, the camshafts have a cam timing "slot" cutout next to the camshaft bearing at the front, and a special tool fits into this to lie on the flat surface by it. When you get the tool, you'll see how it fits. Also see the webpage below

Quote:
Thirdly.... The manual suggests that I use a special tool to for the chain tensioner when I finally get to removing the cam sprockets. Does the tool still exist? Is it essential or is there a work around?
This special tool is for adjusting the top cam chain and, of course loosening it prior to removing the cam sprockets from the cams. Adjustment is via the central idler/tensioner sprocket accessed from the circular plate at the front of the head. You will find a clampiing nut, which you loosen then use the tool to turn the sprocket axle on its eccentric bearing axle to tighten/loosen the top chain. The bottom chain is hydraulically tensioned, with a tension that also has a spring and ratchet to take up wear, and keep tension whilst oil pressure builds.

This webpage has both tools on it, with pics. As you'll see, they are not expensive, and are also essential to doing a good job !

SNG Barratt - UK | Accessories

Quote:
Fourthly ... When it comes to re-assembly another special tool is apparently needed for timing. Some say that they made this tool themselves... where can I get a template to make my own ?
See above

Its a lovely engine to work on, I always used to love working on mine. Of course over the years of development from 1948, some flaws got built in, the original engine of 3.4 litres was probably the best, especially those built in the 60s. The V12 was meant to replace the six, but the oil crises of the 70s and subsequently, meant it never did. I remember having fuel rationing chits in my wallet in around '75 or '76. I never had to use them, fortunately !!
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Old 12-16-2011, 12:42 AM
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The socket your need to turn engine is: 1 5/16"
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Old 03-09-2012, 05:15 AM
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Still going...

I am grappling with the timing chain tensioner. I cannot seem to push the button locking thingy in far enough for me to be able to turn the timing chain tensioner adjuster. A wise man once said ...........

"BTW, if the little detent/peg thingy won't push inward so as to release the adjuster wheel, it can be carefully pulled out (I used vice grips) to clean the baked=on oil varnish/deposits. Don't lose the spring!

After cleaning it back to shiny metal, and cleaning the hole it goes into, it can be reinserted and should move freely."........

Is there any particular reason why the little detent/peggy thing can't be pushed in far enough to clear the cog?

Are there any tricks to putting the little detent/peg thingy back in, if I was to remove it?

What is the normal position for the little detent/peg thingy when it is back in place?

I have attached two photos... one with the little detent/peg thingy pushed in as far as I can get it, the other tempting me to pull it out completely!

Rhys
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Head gasket replacement-button-.jpg   Head gasket replacement-button-out.jpg  
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Old 03-09-2012, 03:42 PM
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OK, if you're having trouble, just remove the adjuster plate, and the detent button will be free to come out. It is designed to be retained by the plate, the bit in your picture is half of a machined piece of circular steel rod, the other half butts up against the back of the plate.

Remove the large nut in the picture and pull the plate off the adjuster shaft and detent button, taking care not to lose the detent button and spring in the engine, or somewhere in the workshop floor.

When you have the head off, clean the adjuster parts with cellulose thinners to remove the varnish and it will all then go back together as Jaguar intended. Of course oil liberally on reassembly.
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Old 03-10-2012, 10:23 PM
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Default Head gasket replacement

Quote:
Originally Posted by Rhys View Post
...I am about to start the process to replace a head gasket on my '86 Sovereign...
You've been given excellent guidance and recommendations throughout this thread, but what exactly is the reason for embarking on this work? Forgive me if I missed it in the thread, but it's important to determine why the head gasket failed: due to overheating, leaking coolant or oil or lack of compression. Or were you merely wanting to decarbonise the engine?
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Old 03-14-2012, 03:32 AM
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Thank you NBCat...

...you are correct... I have been given excellent advice, and have been working slowly towards the removal of the head.

The issue is coolant in the oil, but no instance of overheating or poor performance. I suspect that is is a damaged head gasket, and have embarked upon, what has turned in to a lengthy task. Once I had noticed the discoloration of the oil, I stopped driving the car and sought advice from various sources.

Not having worked on a Jaguar engine before, I am hastening slowly. (Landscaping our new house has been a major consumer of time.) My major stumbling block has been the timing chain tension. I haven't been able to release the tension with my "home-made" tool and cannot get the serrated plate off to release the tension on the chain..... so the head remains on, firmly torqued down and silent witness to my frustration.

I am now considering purchasing a proper timing chain tensioning tool, but am yet to be convinced that I will be any better off.

Rhys
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Old 03-14-2012, 03:56 AM
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Coolant in the oil can get in in a variety of ways.

One possible way apart from HG failure is corrosion of the timing cover near the coolant port into the block. This passage is there for the water pump bolted on the outside of it to pass coolant into the block. The web for the gasket is not all that wide, and if previous users have been lazy/mean with antifreeze changes the aluminium corrodes away. Of course in Australia it doesnt freeze in most places, but corrosion inhibitors are still essential to the XK engine.
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Old 03-15-2012, 01:31 AM
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Sometimes one must become aggressive with the tensioner to get it to move, so use your imagination within reason! Plan on replacing the tensioner once the head is removed.

Fraser mentioned a good point about the cylinder head surface being corroded due to poor maintenance. You may need to weld some aluminium to the head and then use a surfact grinder to bring the surfaces back to their original shape. A good machine or specialty shop should be able to competently perform the work.
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Old 04-09-2012, 04:11 AM
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Default re-assembly

OK, Head off, engine bolts replaced, head pressure tested, checked and valves done.... ready for re-assembly!....

... thanks to all those who offered advice.

I am about to put the new core plugs in to the engine block and have read and seen different advice as to whether to insert them "dry" or to use some sort of sealant or "gasket" cement.

Without creating a great debate, anyone with a definite opinion on the way that the plugs should be replaced?

regards,
Rhys
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Old 04-09-2012, 04:11 AM
 
 
 
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