cooling my slant 6

Not sure what year you are working on so,here goes,, If you don't have a coolant return bottle then the system is constant loss. No problem with the 4 blade fan on a slant. Check thermostat, and radiator condition for blockage and or flow.When doing any repairs such as water pump replacement now would be the time to replace all hoses and flush the system then replace the thermostat. If the radiator checks out ok you should be good to go.