Yes, I've checked that the valve is moving fully and the cable is not slipping. Interesting about the hole always allowing flow. this could be it but I don't think it flowed through when I bench tested it. Perhaps the water pressure in my house wasn't enough. And maybe when I first installed it the outside air coming in was much cooler because the air temp was lower and the engine wasn't up to temp? I'm just trying to figure out if its working normally before I pull the bugger out. Not easy with the heater box installed...