I read it as welding the slots in the block.
welding cast iron is even trickier.
Carl
So: We know exactly where the weeping is occurring thanks to some excellent photography. Would it be plausible to grind out the weld in that area, reweld, and remachine? Or might there be some simpler fix?
The cylinder head had the corroded coolant passages TIG welded and then machined back to slots and the head was skimmed
I have not done anything to the block but a PO has fitted something into the slots that looks like brass. I need to investigate further.
Originally the coolant seep was into #01 then it moved to #03.
Have you minutely inspected the head job, Andy - after skimming the welding should be āinvisibleā. Ie, running your finger over the weld; you should not feel the any difference from any other part of the mating surface - if you can feel it, it is suspicious. You should of course clean and inspect the headās combustion chambers for sign of cracks - though it should not move from 1 to 3ā¦
Those ābrass fittingsā seems out of order - if there are corresponding holes in the head and the gasket they are supposed to be open as part of the coolant circulation?. However, blocking them should not cause the leaks observed - but it may interfere with cooling. Itās the sort of puzzling things POs sometimes leaves us, and you are likely the best judge on whether the openings can be restored. Whether it is worth while is arguableā¦?
Point is that there are no obvious reasons for the leakā¦
Frank
xj6 85 Sov Europe (UK/NZ)
The repair to the head is not invisible, I must admit. There are some small imperfections but it is a huge improvement over how it was, and frankly the best that I think I can get with the skill level of local machinists in Thailand.
The corroded passages were on the exhaust side of the head along the edge. The holes at each end of the slots are much nearer to the bores, and also the studs themselves, which are wet, are nearer to the bores, so perhaps more likley to be the source of the seepage. I think I need to concentrate on those area for next attempt as well as the cleanliness of the block face.
Am I right in thinking the flow of coolant is from the water rail, into manifold then the head, then down through the block? If so, then the ferrules in the holes at the ends of the slots will be restricting that flow and perhaps therefore a possible problem area?
Unfortunately I am going to be away from home for some time on this work assignment so canāt get stuck into the engine again for a while.
Other way around: in through the block, up through the head, out the manifold/ rail, into the radiator.
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As Paul says, Andy; the other way around. The pump receives coolant from the radiator hose - and pumps it into the blockā¦
The flow itself is not leak inducing - but the pressure, as engine heats up, definitely is. However, the mere presence of coolant only needs a chink in the armor to leakā¦
Frank
xj6 85 Sov Europe (UK/NZ)
Time for an update on what has become a saga now with my slotted block engine.
I took the head off again and decided to remove all the brass inserts that a previous owner had fitted to the slots between the cylinders. There were ten round holes filled which all came out and five slots, of which I could only remove 3 of the infill pieces. So then I decided to remove the engine and strip it, then get the machine shop to remove the last two infill pieces and skim the face of the block.
All that work was completed , and I rebuilt the engine. The pistons and bores are still standard and in good condition. The big ends and crank bearings are all +10 thouā and in good condition, so I put it back together without any rebore etc.
I used another new head gasket (MLS type) and a new set of head nuts (all of which I checked for adequate number of threads to tighten without bottoming out).
After all that, the problem of coolant loss was reduced but still remained. This time it moved to cylinder #05. So it started in 01, then moved to 03 after head skim, then 05 after block skim.
When trial fitting the new head gasket, I found that the alignment is very poor. Itās position is dictated by the outer 4 stud holes. This locates the gasket a little too far forward on the block for cylinder 05 to have a chance at sealing reliably, at the point where there is minimal land between the bore and the slot. The photos below show the area between cylinders 5 & 6 with and without the gasket in place, from which it is clear there is insufficient gasket area at the point mentioned.
I tried modifying the stud holes in the corners of the gasket to make the gasket sit about 1mm further back and re-assembled, before fitting the head, but as the head is lowered onto the block it is impossible to judge exactly how it all ends up. Anyway the problem persists.
Next, I am going to try a Cometic gasket instead, I have contacted Cometic and ordered one, but they only make to order and lead time is 6 weeks.
You could glue the gasket in place with some crazy glue in a few spots. Trying is cheap?
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Even with the modification, Andyā¦?
The slot is just to prevent block cracking, it is not meant for coolant circulation - and the gasket should seal/block it off from the head? There is no corresponding slot in the head to allow coolant circulation?
The mating surfaces must be āperfectlyā smooth. ābetter than it wasā may not be enough - and there must be no ātwistā to either surface. Itās prudent to verify that the studs protrude equally to ensure they bottom out in the block - and verify that the hollow in the nut is ample to accommodate head torque and gasket compression, of course. But a micrometer may be better than thread counting - or as a back-up? Given all this is OK; correctly torqued with the correct gasket - there should not be any leaksā¦
Frank
xj6 85 Sov Europe (UK/NZ)
Blockquote
Agreed. The gasket should seal off the slot from the head (which has no corresponding slot).
I am sure that the coolant seepage is from the slot, and the main reason being too little gasket area due to the poor gasket location. The amount I could relocate the gasket rearwards was limited by the rear pair of bores, because then the gasket started to have too little surface area by the slot between #01 and #02.
I do not think the coolant leak is in the area that I had the repairs to the head done. When you look at the mark made by the gasket on removing it again, the gasket surface seems perfectly adequate in the area around the coolant flow passages between block and head now, whereas originally this was a problem area.
I have now bought an engineerās straight edge and am convinced that the surfaces of the head and block are true.
My opinion is that the standard gasket is not manufactured to precise enough tolerances. Perhaps OK for a non-slotted block, but not good enough for this version. The sealing rings for the six cylinders are not accurately centred on the bores, hence inadequate gasket material to create a reliable seal. This is why I have now ordered a Cometic gasket. Below is a pictue of the last head gasket and you can see that the slot has not been adequately covered by the steel of the gasket. I think this should deform down ito the slot and seal it like the lid on a tin of treacle, but in this case the gasket is offset to the front too much.
I wonder why Jaguar chose to alter the block from the original 3.4. In my earlier even more naive days, I poorly rebuilt the 3.4 engine in my Mk1 and proceeded to thrash it mercilessly. It was subsequently sold to a chap who fitted it to his stock car ( capacity limit of 3.6 IIRC, so no 3.8ās ) and won the local championship 2 years running, against mostly American small block V8s. Those 3.4s were unbreakable in their original form, why change a winning formula? The best iteration of the XK?
Maybe because it was an improved design and could be sold as such, maybe they could use some of the 4.2 equipment to machine it.
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Improved in what way? It seemed bullet proof as it was, something it seemed not to be in its later form. They never used much oil, never cracked between the liners nor blew head gaskets, as I recall. I donāt have any personal experience with the later 3.4, but, with the asymetrical bore spacing, were they as smooth running as the original? Long head studs and their propensity to corrode and break? Not my idea of progress.
I do think the slots between the bores are a good idea (as long as the gasket or block isnāt out of tolerance?) and I also believe that larger bearings cannot hurt. The long studs are a failure when it comes to longevity but otherwise seem like a good design choice.
Considering that Iām sure the earlier design was a good one and there was nothing wrong with it.
I am guessing only because the larger displacement versions had more torque and power, but that introduces new problems, (same as other makes)
Talking to our local jag Pro, for sure the 4.2 blocks have an issue with liners moving down, and he wont warrant a rebuild without new stepped liners.
I dont know if there is any way to check or prevent this issue
In the case you receive a Cometic gasket, you can only but fit it and see
The new and old 3.4 were carbed and not hugely powerful so that wasnāt the reason they made a completely new pattern (if they did).
I havenāt heard of liners moving down yet and they can definitely take several tons of pressure and not budge, especially now that they have rusted in place
I had to adjust my head gasket (same as the one in this thread) a bit as it would not fit the four studs by a mm. Simply filed away a little and then it seemed to be good.
I am certain both these topics have been discussed in here before, as to why the cylinder & head are not aligned, and the liner issue, and would be in the archives
The slotted block does not have liners
I hate to say it. That block is flawed. A prior machinist soght to save it by fling the slot.
The bore is too cse to the slot. there is not enough metal for the gasket to seal. Teh coolant is seeping from the slot under the gasket and in to the bore.
Back to the filed slots and a better gasket?
Or a better block
You can āstickā he gasekt to the blck to keep it from moving. A copper sray is available for questionabel surfaces.
Or, a semni bodge. Block seler. Not Barrās leak. it is a substance that seeps into crevices and then with heat crstilizes to form a seal.
Wors in small seeps.
Carl