Get a Helm manual for your car. It has a section about replacing the accumulator (that 'gold tube'). It sounds like that's the problem. You do have to relieve the pressure so you don't hurt yourself. If I try to simplify the procedure here, I'll probably leave out something important. You'll have to bleed the ABS after, probably have to bleed the main brakes too.

If it cycles on & off fast enough, it'll set off the ABS idiot light. If that hasn't happened, then maybe it's not really bad?