[nursecosmo]

Three weeks ago I replaced the water pump and thermostat. a couple of weeks ago I developed a bad air leak in the front tank fuel line ( the back line has had a leak for a month or so). I replaced the fuel line then discovered that the stock fuel pump was leaking air so bypassed it with an electric one. there is no more air getting into the line but for some reason it overheats. there is no bubbling in the coolant or coolant in the oil so I really don't think there is a head problem. when I pump on the priming bulb to add a little more pressure it seems to make the thing run cooler. can under-fueling cause overheating? all cylinders are firing as far as I can tell is there really that much cooling effect from the fuel? has anyone run into this problem before?

 

[sle2115]

Do you have an aftermarket temp gauge? You aren't relying on the in dash temp gauge are you?

 

[sootieoil]

[ QUOTE ]
Three weeks ago I replaced the water pump and thermostat. a couple of weeks ago I developed a bad air leak in the front tank fuel line ( the back line has had a leak for a month or so). I replaced the fuel line then discovered that the stock fuel pump was leaking air so bypassed it with an electric one. there is no more air getting into the line but for some reason it overheats. there is no bubbling in the coolant or coolant in the oil so I really don't think there is a head problem. when I pump on the priming bulb to add a little more pressure it seems to make the thing run cooler. can under-fueling cause overheating? all cylinders are firing as far as I can tell is there really that much cooling effect from the fuel? has anyone run into this problem before?

[/ QUOTE ]
when the truck is hot run your hands over the radiator and make sure the whole rad is hot, any cold spots and the rad is bad.
make sure you turn the engine off ok. unless you have no a/c condensor then you can run the hands over the front side of the rad all you want. hope this helps /ubbthreads/images/graemlins/biggrin.gif

 

[cdnsarguy]

[ QUOTE ]
I replaced the water pump and thermostat

[/ QUOTE ]

Which one did you use.......I bet an aftermarket one.......

CAUTION:
The specified/required thermostat does not contain an internal bypass, since the bypass is located in the cylinder block. Whenever the thermostat is replaced, it is mandatory that only Motorcraft E5TZ-8575-C or Navistar 1807974C94 thermostat be installed.