my 92 5.0 never overheats, passed a pressure test and a block leak test has a new radiator cap and a properly installed oem thermostat. I flushed and filled the radiator and really didn't get any crud out. Pushed water thru th radiator and block with no problem at all. That being said it never builds pressure in the upper radiator hose. Every vehicle I have ever owned pressurizes the upper hose and i believe they are all supposed to. If you pull the heater core hoses or any other small hose it pumps coolant out like it should with the car running. So with a hot engine it should heat the coolant and cause pressure in the system, it does not. You can pull the radiator cap whenever you want and not spill a drop. What gives?