tuck

I am having intermittant overheating problems, replaced t-stat, fan clutch and water pump and it is still overheating. it will spike the temp and i will turn the truck off, wait a couple of mins and restart the truck and the temp will be back to normal. Any ideas? It will also run rough when cold until it warms up then runs smooth. I have replaced the coil packs, swapped the coil packs, replaced the plugs, and the IAT sensor...still no change always throws the service light for misfire cylinder #1. This is on an '03 4.6

Good old Bill

Sounds like the indicator system is malfunctioning. An engine cannot cool down from overheating to normal in a couple of minutes. How long does a pot of boiling water take to cool while sitting on the stove?

ScottyD

replace temp sending unit specify for gauge not for computer

tuck

I thought it was the gauge at first as well but it actually gets to boiling over (or at least spitting fluid out of the res tank) and then back to normal in a matter of minutes.

ScottyD

the res tanks cap rasies the boiling point of the coolant so maybe its bad, real cheap to replace, any parts house should have it

98 f150 nascar 5.0

i have a 98 4.6 or i should say i had its a 5.0 now but when it was a 4.6 i would be driven and runing fine the temp just go all the way up over heating light would come on than i just give it a lil gas 4 or 5 sec it go back down than sometime eng light would come on and it b a mis fire in cyc 4 i did some testing and it was a head gas on its way out frinend of my had same prob danyf150nascar@yahoo.com