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Bronze castings

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In connection with my exhaust-gases-in-the-coolant problem, which may be a leaking head gasket (the best scenario), I thought I would try the block sealer approach (sodium silicate solution, KW Permanent Metallic Engine Block Sealer) since I didn't see how it could do any harm provided I didn't block any passages through my priceless honeycomb radiator. So I removed the radiator, bypassing it with a big hose, flushed out the system (although there was no antifreeze in there), put in the stuff, ran the engine until it boiled, let it cool, drained and flushed.

However, during the course of this exercise I had a disaster. I broke the cast-iron casting that forms the container for the thermostat, in two ways (the mounting flange and a hole in the side). It might be reparable, but only if I could remove the thermostat inside; it is brass or bronze, about 2.5 inches in diameter, and screws into the iron casting. Of course, after 80 years, I cannot budge it, despite soaking for days in penetrating oil. I rather doubt that it is going to come out intact.

I am therefore considering taking a hack-saw to the casting. Once I have removed the thermostat, I could glue the casting together again with epoxy. The result could presumably be used as a model for a new casting, preferably bronze so that it won't build up rust on the inside. Does this sound feasible, and if so, can anyone recommend a casting company, preferably in the San Francisco Bay Area?

Ken G, 1925 Rover 16/50 (San Francisco)

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Hi Ken,

Don't cut just yet. First take some measurements of the casting and jot them down, they are actual to the part and period. Second, if you can, make a "jig" from wood and bondo and secure the casting (wax it first) to the wet bondo and wood. This will give you a fixture to epoxy the casting back together filling "just" the saw lines. Castings are like a solid print, exterior first and interior second. You are going from iron to bronze so the shrink will be different and measurements will be critical. I did a "Thomasnet" search and didn't find any bronze foundries in your area. You might try a yellow pages search of 'Frisco and Oakland and see what comes up, there may be one not listed on my search.

Oscar Merrow

(Prime Pattern)

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Many thanks for the comments and suggestions.

The brass or bronze thermostat has a greater coefficient of thermal expansion than the iron housing. A friend has suggested that I try dipping the brass end (which projects out of the iron casting) in a slurry of dry ice and acetone, and heat the outside of the iron, in the hope that I can induce a sufficient temperature difference to allow the thread to let go. I am skeptical but I can see no harm in trying. Not that I want to, but I dare not heat the thermostat above boiling because I think that would destroy it; indeed, the whole object of removing the thermostat is so the casting can be made very hot during repair.

If that fails, yes, your idea of making up a jig to assist in gluing the sawn bits together is a good one. I also take your point about shrinkage. Fortunately the dimensions are not at all critical, apart of course from the threaded bit, and on a new casting the thread would have to be cut on a lathe anyway.

I rather like the idea of replacing the iron casting, which of course is all rusty inside, with a bronze one. I suppose alternatively the main body could in fact be turned, and then welded to a flat plate to form the mounting flange. Actually, as I think about it, that sounds a more practical, and perhaps less expensive, approach. I have an acquaintance who is retired but still has an extremely well equipped machine shop; I should consult with him.

I will post results in due course.

Ken G, 1925 Rover 16/50 (San Francisco)

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