I have a 1998 f-150 with 4.6. I changed the rad, all the hoses,flushed the eng.twice, replaced every sensor. changed the oil and evey filiter.installed a new manual water temp gauge and I disconnected the electric one ford had in the block. the eng.runs real cool at 175 to 195 does not over heat then when you run it on the hw. it spikes,and the oil lite comes on.my wate temp ga. read 185.i pulled the wires off the ford sensor. and the it still spikes how can the needel move if it is not hooked up?i install a dbl thick rad twice as thick as the ford one. enstalled all ne anti frezz.in the city it runs good until I push it on the hiway. I have 149000 miles I change the oil every 3000 miles or less. I check the oil every day.i replace ever spark plug all the wires. the egr valve..i must have a bad ground wire some wire...next step is to enstall a oil pressure gauage. and ditch the ford cluster gauage. .
any help, thanks.