I had a similar problem... One of the "T" valves for the headlight washers was cracked or something (nothing visually wrong..except for fluid dumping out of it) When I filled the washer fluid level above the height of this valve the fluid would naturally leak out. Open your hood and near the headlight somewhere ( i dont remeber exactly where) you will see what I am talking about. Just trace the line from the headlight, you'll run right into it. This is on the passenger side of the car, not sure if there is a valve on the left side. And you're probably thinking, "but mine isn't leaking up from near the headlight", well check it anyway. When mine leaked the fluid hit several things on its way down, by the time the fluid hit the ground it looked more like it was coming from the filler neck. Anyway I hope this helps, and this part is also cheap to replace in case you are wondering.

Good Luck

DG
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1998 S70 T5M