I built my own set up. I can hear the pump when I'm stopped. It's a tilton pump. Above 10 MPH or so I don't hear anything. In typical just running on the interstate I don't hear it until I exit and stop. I happened to notice the 30 minutes at 80MPH at 80*F ambient because that's how long it took to get from where I lived to Woodward Ave. I think I'd hear it less if I didn't have a wagon. Having an enclosed rear compartment to trap the sound really helps with rear NVH type things.Which cooler are you running? How do you know the pump is kicking on, can you hear it?