Saw your post and took a look through the 126 CD I've got. It appears the 81 originally had a heat exchanger heated by engine coolantto keep the washer fluid warm. If the heat excanger is gone that might be what the hole is for! Does your still have that feature? Your washer fluid hoses and nozzles are heated electrically also originally. It appears that you should have two pumps - windshield and headlights, and a level sensor on the tank.