the dealer had the check valve set to pull antifreeze
Just to be technical for a minute: You can't "set" a check valve. There is no handle or anything else on a check valve that can be set. If the valve has a handle, it's just "a valve."
A check valve is typically just a valve seat with a spring-loaded ball. Water flowing in one direction pushes the ball against the spring, opening up the space between the ball and the seat and letting the water flow. If water tries to flow the other way, the spring (and the water) pushes the ball against the seat and the water can't go through. Hence "checking" the flow.
So what I think you're saying is that there is a normal handle-operated valve between the pump and the AF connection that was left open?
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