86 f150 overheating

got a 86 f150 inline 6 300
i have changed the thermostat , thermostat housing, checked heater core ( not clogged or damaged. and it still over heats.

could this possibly be a head gasket or should i check the thermostat to make sure it is still working right?

i started the truck w/o the raditor cap on and the water was throbing back and forth, so it was moving so i assumed the water pump is ok.

any help would be appreciated.

thanks

could be head gasket ckeck oil see if it discolored or kinda milky or radiator could have some rust or calcium build up. not allowing enough coolent to pass through the fins of the radiator.

the oil isnt waterery, theres no oil leak, i have the same oil amt and i havent lost oil pressure. is there anway of testing for both ?

The easiest way to tell if your coolant system is clogged is to run the engine with the thermostat out. If it still overheats, with no water in the oil, and no oil in the coolant, then the there is an obstruction in the coolant system. Have a radiator shop flush the coolant system. If the engine does not warm up at all then it is a faulty thermostat. I have had thermostats come from the parts store bad. I had to go to the store 3 times for the 79 pickup I had with the inline 6.