Temperature sensor

[firedrake1942]

Never, ever seen that before, but It can only have come via a failed head gasket, I suspect. The gasket is supposed to seal the various oils and water / coolant chambers and channels from each other and from the head studs. Which head gasket did you use? There is some evidence that modern ones are less robust than the old stock.

[philthehill]

There should be absolutely no coolant seepage past the cylinder head studs.
Sealant should not be applied to the cylinder head studs.
You can give a light smear of LM grease to both sides of the head gasket before fitting which will help with sealing and seating.
When you tightened the head nuts - what torque did you tighten them to? & did you tighten after the first heat cycle?
The top of the block where the cylinder head stud fits into should be countersunk as the top of the block pulls up when the head nut is tightened and stops the head and head gasket seating properly.
I personally would not worry about the small amount coolant going past the plugs - just remove the plugs and spin the engine over to clear the bores and once that is done give a few squirts of oil down the plug hole - refit and tighten spark plugs

[Pucketsport]

Thanks Fire-drake and Phil. So I purchased the gasket from Moss Europe and it wasn't cheap so I can only assume they sell a good product. I also torqued the head bolts to the correct torque and to answer your question Phil It has never been started so there was no re-torque after the first heat cycle. I don't believe it is a head gasket and/or torque issue as the only leak was out the top of the studs.
I opened the engine and found that there was hardly any water on the pistons and what was there ,probably went down the spark plug holes which I foolishly left finger tight.
I confirmed that the holes for the head studs are drilled right through into the water jacket ( by design) and therefore there is every reason to expect the coolant to find its way up the threads and out the top of the cylinder head bots ( there is no inherent water tight design.) I could try and tighten the studs firmly into the block so that the smooth shank buts into the block but that also would not necessarily guarantee a seal ( steel on cast iron).
Phil you say there is no sealant used on the studs , how are they supposed to seal the water jacket from the stud exit point ?

By the way I was told to only finger tighten the studs into the block so that could be the problem?????

[philthehill]

The action of tightening the head nuts pulls the threads on the studs and the threads in the block together and causes the threads to mechanically seal in the block.
I have enlarged your pictures and if you look closely at the area of head gasket between the R/H stud and the piston and the nearest coolant transfer orifice it does not look too good, it looks as if there has been no real contact between head and gasket. If there has been no real contact the coolant can easily seep through from the block and up the studs.
See also the head gasket sealing ring around the bore aperture it looks as if there has not been contact with the head in some areas and the copper does not look good where it joins the sealing ring.
If that is replicated around other areas of the head gasket the head gasket is not suitable for use and should be discarded.
Have you checked the top of the block and the cylinder face of the cylinder head for trueness? It looks as if you have had the top of the block skimmed but it still needs to be checked for trueness.
As regards fitting the head studs to an 'A' Series - some head stud manufactures recommended that the head studs are only hand screwed into the block and not tightened.
I have never had to use sealant on the stud threads where they fit into the head though I have on occasions tightened the studs into the block and hand tightened them as well - both ways were done with no ill effects such as coolant weeping.
Phil

[Pucketsport]

Thanks for all the replies. Just a point, there was no transfer of fluid across the head gasket. All the fluid came up through the studs and out the cylinder head nuts. Its also worth pointing out that the 4 "inboard" studs did not leak at all and I noticed they are blind holes.
I mentioned this to one of my Colleagues at Ford who works in the Engine lab as he has worked on many old cars including a Morris Minor. He said it was standard practice to seal studs where the threads went into the water jacket. He mentioned that the original Holdens had the same design and they used a Permatex product to seal the studs.
The action of pulling the studs up when tightening would simply seal the upper surface of the thread and open up the lower surface. Thats why we have tapered threads when a seal is required.
Anyway I'll try thread sealer and see how it goes.
Thanks again
Andrew

[kennatt]

very strange, I've rebuilt about 10 A series over the years ,never used sealant and never had this problem ,I suspect the head is warped and would have it checked first. If you think about it with the number of threads on the stud you have a massive interface with the block each one sealing when pulled up so absolutely no need for sealant, never used by factory,but who knows in this case.

[philthehill]

Pucketsport
Many thanks for the reply.
As Kennet points out BMC never used a stud sealant and neither have I and I have rebuilt many 'A' Series engines over many years - including the one currently in my Minor which is fitted with finger tight and oiled ARP studs without sealant. Not a sign of leakage at all.

I would advise again that the faces of both the block cylinder head are checked for trueness.
Even if the top of the block and the face of the head have been skimmed it does not mean it has been done properly. Never accept as is - always check for your self.
Only when you have eliminated all other possibilities of leakage should you resort to sealing the threads.
If your threads are in good condition and have been cut to correct tolerances there will be no pulling apart or opening up of the threads.

[Pucketsport]

Once again I must point out that the leakage is NOT across the gasket, it is up through the stud threads, how can a warped head do this? The head and the block have been skimmed by a professional engine rebuilder and if it was warped why then is the coolant only leaking through the studs ????
Regarding BMC never using thread sealant, where does that information come from ?

[Pucketsport]

Phil can you explain how applying a load on a thread causes it to seal ? That makes no sense. If that was the case then there would be no need for tapered threads. I suspect that all the engine rebuilds that have not used sealant have had the studs tightened up to the smooth shank. It just doesn't make sense that it would seal in any other way. Can you tell me what the flatness spec is for the head and block surfaces are so i can check mine ?

[Pucketsport]

arp-bolts.com/p/FAQ.php
On blind holes use a small amount of ARP Ultra-Torque lube on those threads. Additionally, if the studs protrude into a water jacket, you will need to clean the threads in the block to remove all coolant and oil residue. Apply a liberal amount of ARP thread sealer or a high temperature thread sealer. Are ARP bolts and studs ...
This is from the ARP web site

[BrianHawley]

When I was a kid and we rebuilt mini engines, we would use a thread sealant.

Not sure why. I guess someone told me to at some point.

Not saying it's necessary, but it didn't seem to do any harm.

Can't remember what it was, but it was green in colour.

[philthehill]

The physical contact of the two faces (that is male and female) of the parallel thread if in good condition will seal the threads when they are pulled together under load.
A warped head or none flat surface will allow coolant to creep from the water jacket aperture to the stud hole passage in the head and up the stud/passageway and out.
As I have pointed out and after again looking at enlarged versions of your photographs the head gasket does not look good.
You are right about ARP bolts and sealer - but it is not a prerequisite in that it must be used as that prerequisite is missing from the instructions.

http://arpinstructions.com/instructions/206-4204.pdf

Regarding head/block distortion - If you can get a feeler gauge greater than 0.003" between the head or block and an engineers straight edge then the head or block is suspect.
You may also be right about the end of the threaded section coming up against the block thread and sealing so stopping the coolant passing the thread but in my experience I have never had problems with coolant passing the stud threads whether the stud is very tight or finger tight in the block with non blind head stud tapping.
Non use of thread sealant by BMC - I worked in a BMC garage when Morris Minors were still being produced and sold and had the opportunity back then to overhaul and rebuild many 'A' Series engines and there was no requirement to use thread sealer on non blind stud holes.
All I can do is offer advice on the evidence presented. You have to determine which advice is best for you and act or not in accordance with your decision.
It may be that stud sealer will resolve your problem but all underlying possibilities have to be eliminated.
The advice I have given above has kept me and the many engines (& not just 'A' Series) I have built in good stead for many years and still does.
Phil

[Pucketsport]

Thanks for the response Phil. I see that the ARP instructions do in fact mention using thread sealant ( item3)
Please note Phil that I have the utmost respect for your knowledge and experience and you have been most helpful over the years its just that this issue seems to have people polarised on and off the forum. The issue I have is that even with perfectly parallel threads , there will never be hard contact between the crest of the thread on the stud and the root of the thread on the block so that will be a leak-path for coolant. Some people use a lubricant on the threads and that might be enough to just seal the coolant in the threads ( I'm guessing ). I was told that some engines , when stripped down, have rusty studs ( on the shank) indicating that coolant was in fact in contact with the shank but never made it past the head nut ( possibly because of a thread locking product or a thread lubricant)
I'll check the flatness of the head and block thanks very much for the specs. Do I place the head on the block to check this gap or must I check the head and block separately using a flat edge ?
Happy 2018 Phil
Kind regards
Andrew

[philthehill]

Andrew
Happy New Year to you also.
The engine block and cylinder head have to be checked individually.
The engineers square has to be ridged as any curvature of the square will distort the findings.
It also needs to be long enough to go from front to back as well as across the block and head.
Check the surfaces for trueness in several directions and at several positions of the head and block.
I hope that you do find them true and you can move then to rebuilding the engine.
Please replace that head gasket though.
Phil

[myoldjalopy]

Hello Phil,
Just jumping back to earlier remarks in this thread.........I'm sure you haven't been losing any sleep over this, but I thought I'd let you know that Santa did give me a 'proper job' thermostat housing for Christmas and I have just now been out and fitted it!
Cheers,
Pete

[philthehill]

Good old Santa - he always knows what we need even if he needs a reminder now and then.

Happy New Year to you and have many safe Minor motoring miles in 2018.

Kernow's St Austell Brewery 'Proper Job' is a fine brew though I usually drink 'Tribute' especially as 'Doombar' appears to have changed in taste.
Phil

[myoldjalopy]

Thanks Phil and Happy New Year to you too....."Blydhen Nowydh da" in Cornish!
Yes, Tribute and Proper Job are both fine ales. Doombar is, in my opinion, an unstable beer - I've had more 'off' pints of 'Doom' than any other and would rarely drink it now. Skinner's Brewery in Truro do some good ales too!