I have just pulled my head off my 4.2 injected engine with slotted block. Why do they have coolant going to the head bolts via slots? What stops coolant coming out the head bolts? Should I locktite or anti seize new head studs in?. My head had 2 gaskets. A metal lower one and a usual gasket material for the top one. is this correct?. My thermostat has 88 degrees on it and only gets 4 mm longer when put in boiling water. This does not seem enough expansion. I am in the Norther territory of Australia where the temps are usually 40 Celsius. Should I get a lower temp thermostat because of the heat? Has been running at 100 degrees

 

Washers under the studs keep the fluid inside. Nobody knows why it's like that, it's a mistery.

About the headgasket: There should be 1 headgasket and the other gasket is for the cam cover's (x2)

Thermostat: Might be a good idea. Is it overheating?

 

The chrome domes nuts keep the coolant where it belongs, and you thought it was for good looks?

I use a smear of Permatex #3 on those washers, and never had issues.

That shim as well as the head gasket reeks of some fool milling the crap out of that head, thus the need for the shim to keep compression under control. Another common sight is the 2 washers under the dome nuts, same fool been here.

Stats open about 8mm +/-. I would be using an 82c stat of the correct length. This length has been an issue over the years, and I use an EA Falcon 6 cyl 82c stat in the V12 and the 6 cyl engines, and it is of the correct length to close that by-pass port 100%.

Replacing the head studs is subjective, and a good idea, but they do snap, so think about that one carefully, coz getting that broken bit out of the bottom of the block is $$, when/if you find someone with the gear to do it. Never seize on the dome nuts is a top idea.

 

The washers under the acorn nuts hiding the head on are just plain washers. Nothing special about them so who knows how it seals. The second gasket was a meatless gasket under the head gasket. Only one washer on top. This engine was factory new 1990 and only had 10000km on it when I bought it. Every bolt came out like new and the head came off first time without persuasion . Love to Herat more discussion on that extra head shim . Why are the cooling slots cut so the allow coolant around the head studs? Engine always ran hotter than I liked but got very bad when head gasket repairer was added to coolant. I tool radiator out and found big lumps 1.5 cm ***** of rubber gump in radiator. Getting it cleaned. Don't use the stuff, didn't work only blocked radiator

 

The washers under the dome nuts SHOULD be hardened washers, of about 4mm thick from memory. Certainly not standard washers in any sense of the word.

The "split block" of the S3 engines was an attempt to stop the actual block cracking, as the S2 engines did. The coolant up the studs has been a fact since the "long stud" engines were introduced in the S2 cars.

When yo say "Factory New, do you mean a factory rebuild, or a NEW carte engine?.

Rebuilds were common in the late 80's and early 90's, and the fact there a plain washers under the dome nuts is not a good sign. MY OPINION.

The hardened washers do not settle, so the tension on the head is maintained. With the hardened washers, and the head tensioned as required, they simply do not leak. The system is only under 15psi max, so not a huge issue. The V12 is the same.

Still no answer on that shim, never ever seen it as well as a head gasket, and I have done many of these engines over the years. I know there are head gasket shims on some engines, Toyota Diesels use them, but that is NOT a Jagaur engine.

On the block side of the cylinder head, on the inlet side of the head are 2 casting hollows, right at the edge. They were originally approx 1.5mm deep. If they are not there, the head has been milled by approx 1.5mm, so hence the shim. That lack of casting witness I have seen a few times.

 

Can not see any casting marks. The head washers are as you described. The engine was bought from factory so may have been overhaul. Will look up old paperwork . Should I put any locktite products under the metal shim? Have you any words of wisdoms to get old studs out. Will soak in inox. Might try heat gun with it. Have a proper stud remover.

 

Can not see any casting marks. The head washers are as you described. The engine was bought from factory so may have been overhaul. Will look up old paperwork .

 

The term new is often misused. Rebuilt is a better term. Then comes overhauled.


Rebuilt engines vary widely in quality. Use of a shim to save a head that was badly warped and skimmed excessively is a sure sign of less than top stuff.


Were that my engine, I'd either look for another one, or at the very least a head that wasn't ground into the dirt...


If the studs are out of the block, I sure would use antiseize.


Leak sealants are a poor crutch. Some far better than others.
The crystalline forms seem to work best and not plug passages
that were not intended.


My son has an ancient Case tractor. Coolant was getting into the oil.
It has removable sleeves. He suspected the seals at the bottom.
of the sleeves at the block were leaking. A crystline sealer
fixed that. How long????


Carl,

 

Why Jaguar wanted (or even merely tolerated) wet studs all the thru the heads is a mystery.

Before installing the head I use sealer to turn 'em into dry studs...at least above the deck of the block. A carefully applied bead of sealer right where the stud and the deck of the block meet does the trick.


Cheers
DD

 

My studs seem to have a wax coating on them. I guess to keep them dry. Is this a normal practice and does anyone know what product . LPS 3 maybe?

 

Might be for storage purpose. Wax wouldn't last long in the hot water environment.


Absent Doug's seal treatment waxed or coated in any fashion, still wet studs.


I guess Jaguar engineers relied on us to keep fresh antifreeze in the cars.


Or cynicaly, they will last long enough. Not the advanced age that they have achieved. 20-30 years and going.


Carl

 

The reason there are narrow slots in the top of your block is to prevent cracking between the bores on the previous design. On the previous engines, due to the width of the bores it was impossible to cast cross passages for coolant between the bores, so Jaguar machined side slots in the bores that opened out to left and right side water jackets, then covered these slots with thin liners. Unfortunately, after some use, cracks started at the top of the passages and worked their way up until the deck of the block was reached. The bridge strength of the metal between each bore was now lost, so the deck sank there and the head gasket compression was released and the head gasket seal failed and combustion gases forced their way into the coolant jacket and blew out the coolant.

The slotted blocks achieve a cross passage a different way by machining from above, thus no cylinder liner is needed. By the 80s when this was done, the XK engine was very long in the tooth, having been in production since 1948 !! The much superior AJ6 engine came out to replace it in the early 80s in the XJS and was fitted to the saloons in 1986. Later this engine was made even better as the AJ16

Here is a pic of the cross passages that cause all the trouble. The liner has been removed.

 

Just learned something. Well, it will just go in the trivia department, as I have no XK engines.


I've seen those crescents in another post. I did not realize the liner was out, and thought it was the bore. wow, big trouble.


The term here is/was Siamesed bores. Same objective. Get more capacity from an existing block design. Chevrolet tried to take the 350 CI engine to 400 CI. Worked, but only sorta. Didn't last in production. GM just advanced the tech in the 350!!


Understanding the function of stuff is fundamental to diagnosing what it doesn't do.


Thanks.


Carl