Brake Fluid Leak - advice anyone?

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'77 930 with brake booster: I have a brake fluid leak out the reservoir overflow hose. It's a couple of tablespoons every 100 miles, and dribbles out under the battery where the hose ends.

I thought I might have damaged the Master Cylinder bleeding the brakes (following some threads here). The guys at my shop had never heard of anyone doing this, but I figured I'd give it a try anyway. No help. It is exactly the same with the new Master Cylinder.

There are no leaks at the wheels or wheel cylinders, and nowhere along the brake hard lines that you can see. I have new stainless flexible lines (tried that first, didn't work either), and there are no leaks around them. The drips on the floor come from under the battery, nowhere else, and as far as I can tell there are no brake lines under there.

Am I just overfilling the reservoir? How far up do you fill it? Anyone have any ideas? I don't know what to try next

[makaio]

Sounds like it was over filled to me.

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Then how far do you fill it? I filled it to just level with the seam at the top. It leaks out if I let it until the level is below the band clamp that holds the reservoir on to the booster. Then I get nervous and refill it.