I need to solder some holes in my copper radiator. I tried doing it last night but the lead solder just beaded on the cores.

I brushed the cores, then applied flux, then heated, then melted the solid core wire, but it still beaded.

Any tips?

I don't know if this is correct, but I have always used silver solder to fix my radiators. I have not had one leak yet. It the solder is beading, you may not have it clean enough or hot enough.

make sure you are using the right solder. use a lead based solder and flux core if they have it. clean the shit out of it with a wire brush, then apply the flux heat it till you see the flux change then apply the solder. if you still get beading apply more heat but only if you are sure its super clean. don't try to use silver solder, it has a much higher melting point than soft solder and will get to hot and wick the soft solder for the other joints.

Hey man...I don't have the name of the flux that I use but...it's a liquid type, that I think is acid. It can be purchased at plumbing shops and is in a eye drop kind of plastic bottle. Also try to find someone with older solder 50/50, which is 50 percent lead, new type is 80/20...80 percent tin and 20 lead. Use damp rags out a few inches from the repair to prevent the heat from spreading to the other joints. Clean is the name of the game, a small brass wire brush is a must. Good luck.

This is a subject I actually know somthing about being a plumber and all.. I would use silver solder or some type of brazing rod found at a plumbing supply shop. Be carefull when heating the pipe when brazing cuz it melts pritty easey at these temps.....

<FONT COLOR="Red"> You didn't get the base metal (copper) hot enough to flow the solder. and like everyone has said, cleanlyness and flux are an absolute must. You also have to be carefull not to get the metal too hot or the flux will oxidise and burn off. </FONT c>

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<img src="http://www.lanset.com/ecvslick/wayslicker1.jpg" border="0" alt=""><FONT COLOR="Black">.</FONT c><FONT COLOR="Red">Slick</FONT c> - 83' bobbed & lockt posuer-mall rig & held together w/numerous <FONT COLOR="Red">Clamps...</FONT c><img src="http://www.lanset.com/ecvslick/slick.gif" border="0" alt="">

Thanks guys, I tried again last night and after some major heating of the cores (one was rotten so it wouldn't clean well) it worked.

There are so many words and 'terms' being mis-used on this thread that I'm afraid more harm than good has been offered...

'Soldering' is usually refer to 'soft soldering' and 'brazing' usually refers to 'hard soldering'.

Soft solders are predominately lead and tin based which flow at about 450*F. and are usually refered to as 'lead solders'.

The enviromentalists are discouraging lead being used in house plumbing and that is why it is harder to find good old 'lead solder' and that is why we see so many 50/50 blend 'soft solders'.

'Silver bearing' is a soft solder usually is predominately tin with up to 4% silver. It should never be refered to as 'silver solder'.

'Silver solder' is a 'brazing alloy' that is usually predominalely silver with added tin mostly but can also contain copper, zinc and cadnium. These 'hard' silver brazing alloy 'solders' usually flow above 1000*F.

Car radiators and house plumbing are mostly 'soft ' or 'lead' soldered copper and are rarely exposed to above 250*F. in use due to boiling point factors.

Copper refrigeration lines are mostly 'hard' silver soldered with silver brazing alloys because they are exposed to much higher temperatures due to freon type liqidation/condensation factors.

Silver brazing alloy 'hard solders' are usually graded by what percentage of silver they contain ... e.g. #56 or # 65 or #70... etc.
The higher the number ... the more silver content, the more heat it takes to flow, and the stronger... usually.

Now let's not confuse these two ... :confused: ... ;) !

Thanks for the lesson in solder. So, to correct what I said above, I used SILVER BEARING solder to fix the leaks in my radiators and I have not had any problems.

A trick I found welding pinholes in radiator cores, clean the area with Muratic Acid. This will remove all contaminants from the metal allow the solder to flow smoothly! Just make sure you clean off the acid after you clean the parts. This acid also work good in cleaning the inside of heater cores and radiators. FLUSH WELL, cause this stuff is nasty!
Muratic acid can be purchased at any good hardware store, it's used in cleaning pools...........:skull: