Annoying leak under head nut.

[123-jn]

A few months ago I built myself a 2.1 based in an old early case and did a thread about the rebuild. Unfortunately I had a bit of bad luck and on putting the engine in the first time a valve spring broke, on repairing that another broke and to top off the problems the tappets were not filling properly and were draining down on a whim!!! I Had initially dropped the engine again to check the pressures and heads again, all seemed ok but I had a leak under the front drivers side top head nut, running around the spark plug and down onto the floor. I still had a nasty knock which sounded a bit tappety so I decided to pull the engine a strip it again to make sure nothing serious was wrong.
I took off the heads and fitted a set of new valve springs and split the case finding no witness marks so my case clearancing was ok, but number one liner had started to break up on the surface around an old water mark so I also replaced this liner and checked bearings etc.. I reassembled again and looked carefully at all the head nuts and mating surfaces to see if I could see a reason for the leak. All looked fine so With more yellow gunge I torqued the heads on again and refitted the engine to the van. This time the knock was gone perhaps it was the rings hitting the rough portion on the liner? With the new valve springs the tickover was much more even but guess what still a leak on the same cylinder head stud. I released the head nut and let the water drain the resealed with yellow gunge, there was still a leak. I looked with a mirror and could see the pink coolant pooling under the nut and running down the side of the head. It was also pooling around plug one and causing a misfire!!! So What could I try? I used an m10 aluminium washer 1.00mm thick together with sealant and torqued it back down , surely this must do it? NO still a leak. I am starting to think that there must be a tiny blemish/crack in the casting behind the nut but if there is I can't see it. Does anyone have any experience of this problem?

[itchyfeet]

dirco ht ?


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[123-jn]

Just had a real good look at this problem and used a wire wheel on a dremel to really clean up the seat under the head nut. What I have found is in the crease behind the head nut where the casting increases in height is a hairline crack!!! This is where the coolant is seeping out so it appears that I have yet more work to do on this engine. A head change is required. I have a spare but perhaps it needs crack testing!!!