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I had another look with the endoscope into #03 and could clearly see drops of coolant entering at the top of the bore at the gasket joint.
So the problem is clearly with a lack of seal at the head gasket.
I read on Jag-Lovers forum some discussion about the use of copper size to coat head gaskets. One poster stated this:
“ First, the head and block surfaces should be clean with no grease or oil on the surfaces. You are asking for trouble if you don't. Second, the head gasket is coated with coppercoat on both sides. I have used this method for over 14 years on my cars with no ill effect. I was told to do this by Jaguar mechanics when I was first rebuilding my XK140. Never had a problem. A friend of mine did not do this and had to replace the head gasket on his E-type because of coolant seepage”
This is the problem I am having, so perhaps I should try again and use copper size.
Looking at the gasket, it seems odd to me that all the coolant passage pass throughs have an orange seal ring, but none of the triangular stud holes do, yet the studs are “wet”. Surely they should have that around the edge of the hole in the gasket too?
I had an engine that had been rebuilt, and it leaked at the head gasket. It turned out they used various length studs, and some were too long for the acorn nut to clamp before bottoming out.
To check, I removed the washers and snugged up the nut, then observed the remaining available space. If the space was the same as or greater than the washer, I put 2.
You could test in the same manner without removing the head, just do 1 nut at a time.
Andy, I think the problem is going to be the flatness of face of the block. .003 is too much gap, I wouldn't be happy with anything more than .0005 to .001 with a composition gasket and dead flat with a solid gasket. Did you check the head, same thing there and the clearances can "stack", creating a gap equal to both numbers together. Also, the straight edge you use has to be positively-absolutely straight and machined flat along the edge(s). I use a "certified by the manufacturer" 3'x1/4"x2" steel straight edge in my shop. A carpenters square or hardware store 3' or 4' graduated aluminum straight rule is not good enough.
I know "good luck" are just hollow words about now, but I truly wish you the best.
I was using a standard steel rule as my straight edge, so probably not as accurate as an engineer’s reference straight edge.
I took the figure of 0.004” / 0.1mm as the tolerance as that is what the Haynes manual references. Although Haynes might not be the last word in car maintenance, they generally took their specs from the manufacturer. Anyway, my check result was that the block face was straight to at least 0.004” and possibly better, so I carried on.
If, when I remove the head again, I do a more accurate check and find that it needs a skim, presumably those slots between the bores stay in place and are skimmed too? I think this version of the engine does not have liners. A big job looming if that is the case as I’ll have to strip the engine to a bare block.
I think it is worth trying using some copper size and another new gasket first.
Any reaction to my comment on the lack of orange seal bead around the stud holes in the gasket? It seems to me that perhaps this gasket is for short stud heads and there should he a different version for long stud?
It can't hurt to try it again and it might hold this time. As you've mentioned, there could be other conditions that are helping to create the leak. I don't mean to be pushy, but did you check the head for flat? I'm not familiar with the Jaguar engine, but anything that is present at the mating surface of the block/head needs to be in place when the block/head is skimmed.
I'm sorry, but for the same reason of ignorance, I can't comment on the head gasket.
Is your block a "slotted" block or not ? Previous blocks would crack between the bores and let coolant into the cylinders. At the same time combustion gas would enter the coolant jacket and blow coolant out past the pressure cap. I had this with my engine back in the late 80s. Slotted blocks are not trouble-free either as there is so little metal between coolant and cylinder.
A question on those slots….should the holes at either end be bottomless? I cleaned them out but they all seemed to end about an inch down. I am wondering now if they should be clear through to open space? Perhaps if coolant is trying to flow through these and can’t, I’m getting an unwanted high pressure spot at the head joint.
The slots are there to allow coolant to circulate between the bores. I have never studied a slotted block, the one I swapped my cracked block to in 1990 was not slotted, (and not cracked either !!!).
The slotted blocks stopped the cracking, and no liners were used as Andy T says, but head gasket failures would occur towards and beyond 80k miles. It could be that your block suffered this in the past, and was hurriedly repaired without any checks of the block face. There is little metal between slot and cylinder, so this surface must be almost perfect to allow the head gasket to seal. You really need to check the block surface not just the cylinder head. If the block needs skimming, this is, of course, a major strip-down job, as the engine rebuilder guys will want to receive a bare block to machine. If you do end up doing this, you MUST bolt the timing cover back onto the block so it is skimmed at the same time. Actually, have you checked if the block/timing cover surface is totally flat ? Any lip will end up with head gasket failure. Block and timing cover were always machined bolted up together at Jaguar when the engines were in production.
So good I've bookmarked it !
Especially good for photos of coolant passages between the bores, and use of top-hat liners after cracking between the bores. Of course all this sort of work is NOT cheap !
Each slot should provide a coolant passage across the block between a pair of cylinders when the head is bolted down. At at least that is my understanding, otherwise why go to all this bother ?
Having done some searching around on the forum, I have now come across some photos of how the slotted block should look, and realise that mine has been modified.
How the slotted block should look
One of the slots in my block (before cleaning up) showing some brass or similar insert
So it appears that a previous owner has made a modification to the slots and reduced the diameter of the water passages at either end. I will need to investigate this further and find out if the slots are still open below that insert, allowing water transfer, of it they have been blocked off completely.
Very interesting. I would deduce that a PO had gasket issues between the bores. The fill is to proviide more clamping surface and stop any seep. IO have no idea where the cracks were that caused the new design of a slot . Between the bores at the locatin of the new feature,, the slot. that would seem to relieve the ironand prevent the crackig.
What else mystifys me, is the brass inserts. A relief so as to prevent a crack???
It now is that the block is old tech, No slots.
Perhaps ok. but the fill must be very flat, atthe same level as the rest of the block.
I am finally back home after 99 days away at work in the UAE desert, so got back to investigating this head gasket problem today.
I have removed the head again and had a close look at the slots. Seems the round holes have beein filled with brass ferrules which reduce the bore of the water passage to only 1/8" or so diameter. Between these, the slots seem to be filled with copper. It does not look like the block was skimmed after this was done as the tops of these infills do not feel completely flush with the deck.
I have removed one of the ferrules today by tapping a thread into it and pulling it out. I shall continue with the others tomorrow, then tackle the fills in the slots.
After that I shall clean everything up and check the top of the block for for trueness. I have ordered an engineer's straight edge for this. All the studs are coming out again so that I can get a good go at cleaning up the top of the block. I might have to remove all the core plugs again to clean out the threaded holes in the bottom of the block before refitting studs. All the long studs were new a few months ago when I worked on the valves as most had "waisted" down in the coolant due to rust. I am also replacing the four short studs this time and have a full set of new acorn nuts and washers in case the old threads were stretched.
If the top of the block seems true, then I will re-fit the head using a new head gasket with copper size. If not, then the block will be coming out and getting stripped down to go for machining.
It occurred to me that a carpenter's framig square might be optimized. Perhaps not to the degree of accuracy of a machnist rule. Use the feeler along the edge, corner to cornewr. flip the square, end for end, measure again. if ghe squre is true, the measurments should equal. NMot absolute, but i believe. [robable. I have doine that, it worked
12-26-2021 | 08:05 AM
