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MG Midget and Sprite Technical - Radiator leak

There is a persisitent small leak from the radiator,around the filler neck where it meets the radiator body. (It's a 1275 with a crossflow rad).
Closer inspection reveals the solder/braze joint has a tiny pinhole and is allowing fluid to escape when under pressure.
I've tried several paste/filler solutions but it still persists so the time has come to do it properly. Should it be brazed or will solder be sufficient? I have no experience of brazing so am rather hoping the advice is to solder :)
Jeremy Tickle

Only done it once. Nothing to lose, so I tried it. It was on a Scania truck. Plumber's bar solder worked for me, with a butane blowtorch. But I don't know how long it lasted after that!
Greybeard

I did exactly that on my Frogeye where the top hose connector was coming away from the body of the radiator. A butane torch and plumbers solder, took about 2 minutes and so far has lasted out the year. Just use enough heat to melt the solder in the area where the pinhole is, don't let the heat spread too much.

Rob
Rob aka MG Moneypit

Thanks for the resposnses - Plumbers solder it is!
Jeremy Tickle

Good luck J. BTW I suggest getting it a clean as poss first. If you have a tin of Fluxite some of that will help.
Greybeard

Brazing would be for the brave as the radiator parts are brass as is brazing rod so in all likelihood it would end in tears, you would also have clean off all previous solder to avoid that contaminating the brazed joint. Lead solder is a killer as it micro alloys with the surface so even a lower melting point silver bearing solder would have issues unless you cleaned the joint surfaces right back but they are thin too start with so not likely a good plan and the brazing heat would almost certainly melt any solder joint in the area. As others have mentioned a good plumbers solder (old nasty lead/tin stuff) is likely the best bet, I would chose an acid flux and maybe drill out the pin hole to make sure any contaminants are removed and flux it and go. I prefer an oxy fuel torch for these sort of jobs as it gives me greater control of the local heat but I have that luxury. A straight butane or propane torch can be a bit of a blunt instrument especially if other sensitive features are nearby.
David Billington

Thanks - I'll have to clean out all the filler cr#p so hopefully it should be clean. It's a good excuse to buy a new blow torch as my old one has converted itself into rust. Any suggestions as to a decent make?
My dad had a parafin one which seemed to take him a morning to clean, prime and get going so when the cannister ones came out, he binned it and went straight our and bought one :)
Jeremy Tickle

The one I use is intended for cooking of all things! My wife got one for making creme brulee and I borrowed it for some plumbing work. After that I bought one for The Shed
It's a trigger - control torch which ignites when you pull the trigger and goes out (and shuts off the gas) when you let go of it.
It gets much hotter than a standard butane torch on it's "full on" setting but it's super controllable. It's a sort of forced jet burner, a bit like my cigarette lighter which works in 20 knots of wind You've probably seen that sort of thing yourself.
Here's a happysnap of Chris's torch. Mine was a lot cheaper and uses the disposable canisters, but the same general idea. It can get hot enough for silver solder, brazing and Lumiweld, but turned right down it's fine for soft solder too.
I well remember the paraffin pressure torches. I had one myself. Bl++dy dangerous contraptions I thought. Mine would suddenly decide on a new career as a flamethrower now and then!
As the joint you want to repair is so small I'd probably try it first with my electtric soldering iron, but mine is a powerful (100Watt) trigger controlled iron. Anything smaller probably wouldn't cut the mustard.

With soft solder you're not going to get anything hot enough to do any damage, so you can afford to take your time. As before - best of luck.

Greybeard

Whoops - meant to say David's suggestion of putting a small drill through the pinhole is Solid Gold. Definitely do that!
Greybeard

Thanks Greybeard, I'll spend a pleasant few minutes trawling the web to see what's on offer :)
Jeremy Tickle

This thread was discussed on 08/09/2015

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