OK. Strange problem. I bought a 93 F-150 302 from a friend as a project truck. The fan shroud had falled into the fan when he was driving it and cut the upper radiator hose and another shard hit the water pump hard and knocked a piece of gasket out. The truck was driven hot for about a mile with little water back to his house. My friend was afraid to drive it after that and didn't want to deal with repairs.

I replaced the water pump and thermostat when I got the truck and it was driving hot with the needle in the upper part of the normal range. Thinking it was a stuck thermostat, I took out the thermostat and drove it without a thermostat last week. The engine never got above the bottom of the cold bar.

OK, so I think it's the thermostat. I put in a thermostat today, which I tested several times in a pot of boiling water and again it's running hot. About at the m on normal.

My theory is that the new water pump is a dud. I took of the top hose and the flow is weak and erratic. A surge followed by a trickle.

The engine throws a single code indicating failed EGR function and indeed, there is no vaccuum hitting the EGR valve.

Outside of that, the engine runs great, has lots of power and runs good and cool as long as the thermostat is out.

It is the water pump or should I be looking eslewhere?

 

Sounds like there is air in the system.

 

What kind of shape is the radiator in? It sounds like there is a vortex in the water pump creating a bubble. I can't think of any other reason for there to be a gush and then a trickle of water coming from it. Are you losing coolant anywhere? Also did you replace the fan shroud? They were designed to have one in place, without it the fan/radiator combo isn't going to work too well and could lead to overheating like you're describing. My two cents.

 

the fan shroud is a good place to look, nice and clean cooulant could help, "Ice" or lucas brand "water wetter" might help an electric fan with a good temp relay, how old is the radiator may need replaced if old and nasty coolant has been in it for a while try a lower degree thermostat ford reccomends 185 to 190 if thats to hot go for a 160, i run a 185 in my mustang because i found thats the temp it makes the most power at any hotter and it falls of and even though it sounds weird at 160 it feels sluggish, also if it as an auto trans, buy an auxillary cooler with that can handle 18,000 gvw and put it in instead of the cooler in the radiator dropped temps in my mustang by almost 15 degrees. they are like 30 or 40 dollars at most parts stores and can get pretty elaborate and pricey for a bit more...

 

Thanks for all the responses. I got a mechanical gauge and hooked it into the system. Drove it a good hour afterwards and it stays right on 190 the whole time. I guess the factory gauge wasn't calibrated well and who know why it was varying. I think the engine is doing good though and I think I'll stick with the mechanical gauge.

 

don't run without a thermostat as running at below normal temps can cause a host of problems. sounds like you solved yuor problem though.