Hello , yesterday we installed a new aluminum rad 3 core and a 16" puller electric fan and a new thermostat on my sons 69 Mustang 351 w .It's running hotter than before .We're wondering if the fan is not enough pull for the three core or what the heck is going on . Any of you guys had problems like this ?
Thanks
Gary

 

I'll assume you mean it's running hotter during normal "steady cruise" driving. The fan has nothing to do with cooling in that instance. Air in the system ? Worn out lower radiator hose that's collapsing ? Or the water pump going bad ? Incorrect thermostat ? Faulty thermostat ?

Now if it's getting hotter in park, idling ? Then the fan might not be big enough, air in the system, faulty or incorrectly installed thermostat.

Good luck, and post back with what you find.