In an effort to bring this back to the original topic – yes folks with this problem using the Car Talk search feature will still find this aged thread, so info posted is still worthwhile to them anyway – I had the WW water bottle leak on my Corolla a couple years ago, removed the entire bottle from the engine compartment, and found the leak was where the water exited from the pump/bottle interface at the bottom of the bottle. I removed the pump, applied a little silicone rtv sealant there as a temporary fix, reinstalled everything, and remains leak-proof still.