I have a 1968 Series 1.5 coupe 4.2 with 16,000 original miles and it was bought new by my uncle in California. I recently had work done to it as it had sat for several years, although started frequently but not really driven much. The entire drive train was pulled a new clutch was installed and the head completely redone. it was filled with Clark’s waterless for a coolant. The car runs great except after a long run through the hills of California there is a small SEEPAGE of oil at the front head bolt that runs into the well of the spark plug. My mechanic has tried to seal it several times but the seepage continues. He had told me that it was a problem that may be caused by the use of Clarks as other coolants have a percentage of water that causes a slight rusting that seals the small gaps. What do you think? Any suggestions? Has anyone else experienced this problem? Sorry for the long writing. Love the site and all the great advice from all of you people.
Sorry…It was Evan’s coolant not Clark’s
In the past I had some seepage at head bolts that did seal themselves. Recently after head rebuild I put a dab of RTV sealant under washers and had no leaks at all.
Glenn
Thank you for the info. I will try it and let you all know.
Assuming you have s short stud block the front two stud holes in the block are blind and so shouldn’t be exposed to oil. Are you sure the oil isn’t coming from the cam cover gaskets, which are well known for leaks.
As to Evan’s coolant…trying to be diplomatic here… it’s … snake oil.
Good Morning/Evening Andrew,
Don’t think I’d call it ‘snake oil’ as it does do what it’s intended to do i.e. cool the engine. But I would like to know what your experience has been with it. I have had it in my '68 for ~3 years and have been satisfied with it’s low/no pressure aspects and it seems to cool the engine as intended, they call it ‘lifetime coolant’ but I’m not exactly sure whose ‘lifetime’ so I’m a bit skeptical on that claim-perhaps “snake oil-ish”?
I’m aware of Mike F’s concerns about flammability but if there another concern I would like to hear more.
Cheers,
LLynn
I agree with Andrew; the oil is most likely from the cam covers. Be careful to not over-tighten them or they can crack. Don’t ask how I know this.
You have a 52 year old engine that has 16,000 miles on it………
ANYTHING COULD BE HAPPENING.
I doubt that the Evans would do that compared to a HALF CENTURY of gaskets and antifreeze siting against a steel block and aluminium heads?
Its a half century, RUN the car for hours in heat cycles let things swell up and expand
Check oil for antifreeze….
Everyone is too used to a Honda Accord…….
gtjoey1314
Something isn’t quite right here… Are you sure it is oil that is seeping out, or is it coolant? If it is really oil, then it’s much more likely to be coming from the cam covers and running down past the head nut into the valley. If it is coolant, it is more likely to be coming from under the head nut. Your engine may have been manufactured around the time (mid/late-1968) that Jaguar changed over from the “short stud block” (where the head studs are anchored in the deck of the block) to the “long stud block” (where the head studs are longer and run all the way down through the block and are anchored near the crankshaft main bearings). The long studs run through the water jacket, so it is possible for coolant to rise up the outside of the stud, through the head, and leak out from under the large acorn nut. Even in the long stud engines, I believe that only 10 of the 14 studs are “long” with the outermost 4 being “short” and anchored in the deck, so if the leak is really from the front large head nut it seems odd. Maybe my memory is letting me down again…
The changeover to the long stud block happened early in 1969 S2 model year production, not sure when but around block number 7R2000 or so. If the OP’s engine is original to the car it will feature a short stud block.
The XKs catalog implies that the change was at 7R1915, so early in the S2s. Those engine blocks would have been made in mid/late 1968, but as you say shouldn’t have been fitted as original equipment to a S1.5. This makes it even more likely in my mind that the seepage is oil from a cam cover, not a head bolt. The mechanic’s comment only makes sense if he’s talking about coolant in a long stud engine, and not oil in a short stud engine…
Regardless of block type, there is no oil access to any stud, only water. An oil leak can only come from the cam cover.
Relying upon rust to form a seal is not what I’d call good engineering practice.
How so? Out of curiosity, what evidence (other than hearsay) do you have that you can share?
Thank you for your response. However, the cam covers were the first thing I checked. Nope. Coming from the bolt. It’s oil not coolant.
I am getting very confused. You say that the leak from “the bolt” is oil, not coolant. When you say “bolt”, I presume that you mean acorn nut - there are no head bolts, only studs and nuts. However, in your first post you said:
If the leak is oil, how could your mechanic suggest that rust from a water-based coolant would prevent it? The oil and water circuits never overlap (unless you’ve got a blown head gasket), so anywhere that leaks oil should never have coolant present. I must be missing something…
You are right. It’s an acorn nut. The leak is definitely oil. Not coming from the cam cover but definitely the front acorn nut. Those are the facts. I hope that clears it up for you.
I wouldn’t call it snake oil but if you are having overheating symptoms, like standard coolant boiling over, with Evans coolant the symptom disappears but the cause is still there allowing your engine to run at higher temperatures that intended without boil over.
Its like saying : I kept blowing the fuses for my headlights but after installing a larger fuse the problem was solved. Eventually you’ll find the real problem ( or see it 
)!
If you are overheating find the real problem don’t mask it.
As has already been explained, oil only gets the head from the external feed lines that connect to the back of the head. It is then pressure-fed to the cams, and once into the cam boxes, it drains through the head, and back to the sump at approximately atmospheric pressure.
It would be seriously bizarre for oil to be emanating from a head stud, as they aren’t exposed to oil, and it typically requires pressurized oil to push it past a nut and washer arrangement.
Aside from all that, oil leaking past ANY fastener has ZERO to do with what kind of coolant you are using. I think you need another mechanic.