Soldering Iron Help.

Hi,

I've tried my hand with a soldering iron lately and haven't met with much success. Had a fuel guage sender with a leaky float. Made of copper, had a crack. Tried soldering with resin core and a soldering iron. Looked okay and didn't bubble in a bath, but was sunk a day after reinstallation. Next, I tried repairing the top of the radiator. Had seperated at a soldering crimp. Took it out and laid down a nice bead with silver solder and a propane torch. Tested in the garage, it held water after a few touch-ups. When driven, didn't make it to the gas station and it was leaking almost as bad as before.

What gives? Any advice on what I'm doing wrong?

Thanks for the question.

When you solder floats they heat up and expel air creating leaks. You will need to heat the entire float up with a torch and then solder with the soldering iron. Also, the area you are using the soldering iron is probably not clean. Silver solder is difficult to use and requires the parts be very clean. It also needs higher heat. I would also recommend trying to use a tin/lead solder instead.