JerryB, I've been having the same problem. If I found the right parts, it is actually two pieces. There's a plastic, vacuum operated unit (which I think is called a monovalve), and that is connected by a plastic arm to an in-line metal unit that I assume is the actual shutoff gate to stop the flow of coolant. I thought about replacing the monovalve, but decided to tie it closed as you suggested. When I did, it started leaking coolant at the in-line shutoff valve. When I let it return to the open position, the leak stopped. Any thoughts as to whether I am just forcing the arm too far, or do you think the in-line shutoff is defective? OR, am I totally confused and don't even have the right parts identified?