Couple things .....You have no heater or it's outta the loop?
Ken's correct about flushing everything and the need for a restrictor
If you have time and want to help this pull the freeze plugs and look at the rust....If it's bad
You need to get at the rear one too. I machined the bell housing to get to it easy.Use wire or whatever to get the junk out.
But here's some guesses....Half the rads blocked.Get the motor warm and feel for cooler spots on the rad....better yet use a temp gun to check it
second ...check for a leaking head gasket It's possable to force hot combustion gases into the cooling system underload and run cool at idle You can get a kit that sniffs at the filler for exhaust gases and turns color!!
Third run a water line from the rear of the head to the front where you have this line....
What this does is 1..Allow water to syphon after you shut the engine off instead of blowin out the overflow and 2.. You get ALL the motor filled when you fill the system
Is your truck a pressurized system?
