I'm surprised that your torch still works. I burned one up once when I forgot to turn on the cooler after about a minute of welding. Cost $115 way back when. Looks like your tank is of decent capacity where you should get tired of welding before it gets too hot. If that's not the case, then I might suggest that you incorporate a radiator like an old heater core and either duct it to the pump motor fan or use something like a muffin fan. Be sure to use some anti-freeze or "official" coolant for corrosion inhibition.