Cast iron boiler repair.

knothobber

I have an Ideal Concord 240B cast iron gas boiler, which has recently started leaking water. It appears as if the mastic used to seal the joint face of the two castings is breaking down. Ideal Tech. Dept. were unable to be of any help with the jointing material used. I have the level of competence needed to undertake the rejointing task with a suitable mastic. Can anybody with the relevant experience advise me of a suitable flameproof mastic substitute.

Thanks in anticipation,

Trevor.

SuperTech

Do you have any pictures of the area with the leak? That might be useful with assisting you. I can't say I'm familiar with that particular boiler, but if the sections are leaking I doubt any type of repair short of replacing the leaking sections will take care of it. Is this "mastic" perhaps just furnace cement?

EBEBRATT-Ed

Agree with @SuperTech i doubt the mastic is relied upon to actually seal the water.

EBEBRATT-Ed

Looks like a UK boiler. Found Ideal online but not the OP boiler. Must be an older model.

knothobber

Thanks for the interest shown. Some background details, rather than making the initial post seem like a re-write of "War & Peace". I installed the central heating in 1980, since when it has functioned without major issues. It began weeping some months ago. When cold or at working temp. it did not leak, only weeping for a very short time on heating up. The two sections of the casting are held together by means of four tie rods, which appear to be all that prevents their being separated. Without draining down, I initially attempted to tighten the tie rod nuts, which, being rusty, I first sprayed with release fluid, backed off, applying Copaslip to the threads before initially retightening, the sequence being repeated on each of the four tie rods. The severity of the leak, during this procedure, slightly increased, reducing again as each nut was re-tightened, indicating disturbance of the joint. The nuts were then further tightened, which appeared to reduce, though not stop, the leak. The leak has since become worse, it now weeping from a different point when cold, in addition to the existing leaks on warming up.

Referring to comments:-

SuperTech I don't currently have any pictures of the boiler, but the two initial leaks were definitely from the mating faces of the two cast components making up the boiler. I can't determine the point of the worsening leak as it is within the combustion chamber. Though not familiar with fire cement, as someone from a mechanical background I would have expected some flexible/compressible jointing material would have been necessary to effect a watertight joint between the two cast components. At the points where the joint is visible there has been some material extrusion, I assume, from the tightening of the tie rods, on initial assembly. This material, however, is quite brittle & will break off. Unless this material has embrittled due to deterioration, I would be surprised if it made an effective watertight joint.

Grallert

You could try sodium silicate. Isolate the boiler from the system and drain off some of the water. Introduce the sodium silicate and refill the boiler to pressure. Fire the boiler to limit until the leak stops. Let it cool drain it refill it and see if it works. In my experience at often works on leaking cast iron radiators and cast iron boilers. For how long? had to say, sometime for years.