Tracy D'arth

As the internal pipes on these engines need occasional annealing and have likely been removed and refitted several time it is likely it has been dropped in one one such occasion.

Good, it will stop the moaners going on about being underprivileged.

Our choice, we take advantage of all the rest that the landies don't get.

No reason why it should allow air in if it is assembled correctly. Its a bog standard 296 type filter and there are millions of then in use.

Time to get bodging I think. Get a short brass wood screw and some sealant, anything, silicone, polyurethane. Wrap the screw thread in PTFE tape if you have some, thin string if you haven't, build it up till its as big as the screw head. Coat the whole with sealant. Drill a small hole ( smaller than the screw ) in the pipe or elbow at the highest point where you think the air is and screw the screw in just enough till the leak stops. Dry it all off, the heat will do that, and build up sealant around the screw. Not elegant but it will work. In the old days we would do this without the sealant and solder the screw in but that would involve you draining down. If anyone sees it don't tell them I said to do it.

And I can't believe the price of this, has to be wrong or extortion. https://www.wolseley.co.uk/product/kuterlite-k930-female-iron-reduced-branch-tee-28mm-x-28mm-x-1-2/ This is better but not cheap https://plumbco-online.co.uk/bsp-f-branch-tee-uk-compression-28mm-x-28mm-x-12

Cut it and insert a 28mm compression coupler, at the high point. ( like you used over the boiler ) Slackening a nut will vent it just as easily as a vent fitting. Brass Compression 28 28 1/2"BSP FI tee. https://www.plumbers-mate-sales.co.uk/brass-28mm-x-28mm-x-12-fi-compression-tee---24542800-6888-p.asp but the price is terrible and you need a rad vent plug.

Its only worth cutting the pipe and fitting air vents if there is an air lock at that point. If you check the pipe for fall all along and after tees like that one to the top connection of the calorifier you will find out where there is a high point holding air. Remember that the same applies to the return pipe, it must not have high points that cannot be vented though problems here are less likely as it will vent at both ends and at every radiator tee. You have bled the radiators I suppose? Any valves on the radiator connections? If you cannot achieve a rise from the boiler to the top calorifier connection consider lowering the boiler and the pipe at that end or raising the calorifier, neither easy. Taking the legs off the boiler may be easier.

Its a thermostatic Mira and a very good valve. Will rarely suffer from scaling they were designed for London hard as bricks water. They vary a lot in quality. The better ones like Grohe are all brass insides, the cheapies like Triton are plastic valves inside. Matters little if you let them freeze full of water, they will all break. I would not have a non thermostatic shower for safety reasons no matter how the water was heated.

I am hopefull for tonight, whats left of it. Half a bottle of Nitenurse and I am a but drowzy, I'll give it a try. You are up too?

I had to run a 70' boat south to north and back again to turn at Harecastle because the south basin is too small. Not a lot but enough.

BEngo is partially correct. The single pipe system of connecting radiators is a bit old fashioned and inefficient. It has the advantage here that the calorifier has priority and will heat quicker than if you re-pipe the flows of the rads to the flow pipe. I would be happy leaving the pipework as it is. Similarly in a domestic situation with a large boiler BEngo is correct about the expansion and vent pipes. But on a boat with a small boiler most are done with a single combined fill and vent pipe connected only to the base of the tank. Yours is slightly better having an over tank vent but it is not essential. The advantage of a single bottom connection is that any venting steam discharges under water and condenses straight away instead of steaming your boat out. I would be happy to leave yours as it is or remove the over tank vent pipe. I have installed dozens of boat systems this way. Now to get to the root of your problem. Have you put a small spirit level on the flow pipe all the way along between boiler and calorifier top connection/vent? If you do, I am sure you will find that the attitude of the hull in the water is removing any positive rise in that pipe. In other words you have an air lock in the flow pipe somewhere. Test the rise of the pipe, fix any high unvented parts, then load the bow to get more slope on the pipe. I bet it will work then. It makes little difference whether the pipe rises steadily or goes up high first, its the difference in height between flow and return pipes that determines the gravity flow rate counterbalancing the pipe resistance. What is vital is that it does not have any high part that holds air preventing the gravity flow.

Thanks Richard, confusing my tapers! Its about 25 years since I played with a ST.

but one of them then put labels on the wrong isolator. Put that where it belongs for you.

I think it is not made as pipe. Try Seals Direct and similar companies as a starting point, they sell all sorts of extruded rubber sections including dock edging etc. I find the products of Firestone, Pirelli, Goodyear, Dunlop etc to be suitable, available in various circular sizes.

Make sure you find the marks on the flywheel and I think on the casing, probably with one or the other pistons at TDC. Do line it all up before undoing the bolt, mark everything and be sure you can put it all back in the same place as the flywheel will fit on the crankshaft taper in any position and balance is critical on this engine, the flywheel is an off center balance adjuster I think.

Just a question LadyG, is there anything in the least technical that you don't have troubles with?

The extension drive gear unbolts from the flywheel if I remember, its been a long time since I had a Lister ST3. Then the crankshaft bolt is revealed. The flywheel has timing balance marks that must be lined up on reassembly. The bolt is torqued to 300 ft/lbs, damn tight. Slacken the bolt a bit only, then you need the special puller to pull the flywheel off the crankshaft taper. Good luck.

Dig it by hand and no planning permission required? Really?