Head bolt leak.

[Graham Honnor]

Hello All
I replaced the head gasket on my '37 Ruby engine last week, took it for a short drive to warm it up, and then 
re torqued the nuts to 18lbs on my return and all seemed well.
However, this morning I took advantage of a glorious morning and went on a 20 mile run but when I checked 
the engine I noticed a couple of small water bubbles coming out of the no.1 head nut between the stud and nut.
Could anyone please tell me what the problem is and how best I should tackle it if you wouldn't mind?
Many thanks in advance
Graham.

[John Mason]

Hi Graham, It all depends on where the water is entering the studs hole in the head. It could be that the head gasket is leaking a bit or water is traveling up the threads of the stud from where is screwed into the block. You could try tightening the head stud a little more or if it is only a slight leak some radiator sealant such as Barrs could be used but be careful and follow the instructions to the letter otherwise you could have cooling problems as it will not only seal the leak it can block other waterways and or the radiator.

John Mason

[Graham Honnor]

Thank you for the reply John.
I would rather not use Barrs except as a last resort as the cooling system has never yet been any problem and the rad has a reasonably new core.
I wondered about putting some plumbers thread sealant on the top part of the stud thread and then replacing the nut but was worried about the continuing presence of water in the head stud column.
Is it likely that the water is seeping across the gasket and then traveling up the stud to the top, in which case I presume it's a head off job again.I did lightly smear the gasket on both sides with copperslip as was advised on here and also used new nuts and washers.
I was however very cautious about not over torquing the nuts and I wondered if it might not do any harm to give the nuts another tweak and see what happens.
I'll await any further responses first and see what the majority advises and then choose my next course of action.
Many thanks again.
Graham.

[Chris KC]

Graham,

I routinely torque my head studs to 20lbft. Apply the torque with the engine stone cold by the way, and following the correct sequence (this is important). I would certainly try nipping the head nuts up a wee bit and putting a few miles on the car before having it apart for a couple of bubbles - sometimes these things self-heal anyway. Just make sure water isn't leaking into the cylinders (consider draining down after use while the engine is still hot). Yes worst case whip the head off, remove the offending stud and reinsert it with a bit of sealant on the thread. The only hard part of that is getting the stud out - if it's been put in recently it should come out OK. If it's been in a while you will most likely shear it off then you will wish you'd left it alone.

[Graham Honnor]

Hello Chris
That is uncanny. I just came back in from the garage having re torqued all of the nuts to 20 lb and every one of them took at least an 1/8 of a turn so presumably it needed a bit more of a run than I initially gave it to bed the gasket in. And then I read your post. I must have read your mind also. 
Anyway, I shall do as you say and monitor the offending nut and see what happens and hopefully all will be well.
If not I will be back for even more advice.
Many thanks to you both
Graham.

[Andy Bennett]

Graham
I am far from expert, but I recently changed my head gasket having experienced 'bubbling' on 2 studs followed by a failure between 2 and 3.

Having changed the head gasket I have retightened the nuts to 20lb 3 times over the first 100 miles. They were down to only 16 after the first run of 20 miles and even now I plan to tighten them again after 200 miles.

so in my limited experience they have certainly settled lots (hopefully they haven't stretched).
In the meantime I have decided that it is time for a top end overhaul anyway.

Andy

[Graham Honnor]

Thank you for that Andy.
My gasket went between 2 and 3 also.
Initially I had covered several thousand trouble free miles (engine wise at least) and then snapped 2 crankcase studs
which meant me stripping the engine down and therefore replaced the head gasket on rebuild.
This has only lasted approximately 800 miles and then blew on a local club run a few weeks ago.
Having a bit more time I decided to have a minimal amount skimmed off the head this time by a local firm who are very 
used to pre-war cars and bought new nuts and washers.
I lightly greased the gasket on both sides and brushed a tiny amount on the plain part of the head studs as well.
I was surprised at how much the nuts needed torquing down again for the third time and will definitely follow your 
advice and keep rechecking over the next few months.
It wouldn't surprise me that if I had done this last time I may have avoided the gasket blowing so quickly last time.
You live and learn, even at my age.
Many thanks again
Graham.

[Michael]

Just a quick thought regarding head torques etc. There are some rather soft squidgy washers around which can confuse the issue...beware.

[Terrytuned]

When replacing head gaskets we use Loctite 5990 a silicone copper gasket sealant applied thinly to both sides works on race engines its stocked in Halfords.

[Steve Jones]

When replacing head gaskets we use Loctite 5990 a silicone copper gasket sealant applied thinly to both sides works on race engines its stocked in Halfords.

Me too.

Steve