GL1200 GOLDWINGS

I refilled and bled my front caliper (the one to the hand brake) a few times using Prestone DOT 4 fluid. It has leaked out from around a piston I believe. This is on a 1984 GL1200 Interstate. I am in the process of disassembling and cleaning with denatured alcohol and was wondering if anyone had any ideas why it did this? Was it the fluid? Everything seemed fine for hundreds of miles, but now leaks out in less than 24 hrs. I believe this fluid is synthetic, but apparently all DOT 4 is I think. Do I just need new seals?

Possibly you can get away with new seals, but if you take into consideration the age of the bike the pistons could be badly pitted. Only by inspecting them can you discern what the problem is.