Hi Clifford why do you think most motor manufacturers use a separate washer nozzle mounted above or by the side of the wiper arm, you don't get this problem, my last Mondeo went to its new owner having never had a rear motor and with 270k on the clock, how can something that saturates itself in a mixture of corrosive screen wash and water and then lets it back into the motor gearbox to rot that out be a clever idea, thats built in obsolescence at its finest.
Steve.