Thank you for all the threads on cooling issues and this engine. My mind is going 10 different ways now and I thought I should start my own thread. I bought the truck in July 2021, engine sounds great, manual transmission shifts smooth, A/C works, Heat works, and an all-around great truck. Only 106,500 miles. The only thing I thought I was going to have to do was new tires (two diff. sized tires on the truck). Driving it home from where I bought the truck, less than 10 miles, in Las Vegas with A/C blasting I look at the temp gauge and it is bordering HOT. Turned A/C off, heat on, and got it home safely. Here is what I have done:

1). Coolant Flush
2). Pressure test, had a leak at the lower rad hose to the thermostat. Tighten down and no more leaks.
3). Tested for head gasket leak, and it passed.
4). Replaced thermostat (Gates), Water Pump (Gold Duralast Autozone), Serpentine Belt, Fan Clutch, and Radiator Cap.
5). Ran water through the radiator and water flowed through and less than the hose pressure.

Where I am today:
1). No Leaks
2). Expansion tank (with radiator cap) will fill all the way to the top when the truck gets to 230s - 240s; the upper rad hose is hot; steel pipe coming out of engine matches OBD reads; Lower Rad hose cold; Out hose from the thermostat is hot.
3). Cannot drive long distances without heater running. A/C is a no-no and going uphill is too much of a load.

My concern is the Expansion tank filling that high, when cold it is just below max. Also, the lower rad hose is cold. I have now "boiled" it down to either the Radiator sucks or the Thermostat I put in sucks. It is an electric thermostat. I do not feel great about using the '04 mechanical and letting the other be a resistor, but if that is the answer I can try it. If the truck was built this way, there has to be a reason.

Does anyone know what fuse goes to the Thermostat? I know it reports to the PCM and there are no codes.

Thank you all for your time! I love working on this thing, but I really would like to drive it too!

 

Welcome to the forum

Just as a heads up, the 2.3l DOHC engine uses a CHT(cylinder head temp) sensor not an ECT(coolant temp) sensor for the computer, this is what you see on a OBD2 reader
Not uncommon for these to report higher temps, so need to be swapped out, its between spark plug holes 3 and 4 in the valve cover

2003 should also have a Temp sender for the dash board gauge, its on a metal pipe behind the head near firewall, will have a red/white stripe wire and a black/white ground wire

If BOTH are reporting higher temps then its most likely temp is actually high, lol, I know duh

If temp stays normal at idle and only goes up when when driving at speed then it is most likely a circulation issue so thermostat would be a good bet to start, since you already did the flush, next would be water pump
The heated thermostats were a bad idea, which is why Ford dropped them in 2004 to 2011 2.3l Rangers, also dropped the IMRC
Some chose to use the 2004 thermostats and leave the heated one plugged in but tied up out of the way, or used a Resistor to mimic the heater coil so computer doesn't set a code and turn CEL on full time

If it only gets hot at idle then its a cooling fan issue, fan is only used at idle or when driving slowly

 

Thank you for the information! I swapped out the Thermostat with the mechanical and tied up the electric one and left it connected. Seems much better except going uphill. It will start to overheat (gauge goes past half) and the OBD is reading in the 260's. I just don't understand why it runs fine anytime until it is challenged with going uphill.

 

High engine load, i.e. going uphill, requires a Richer fuel mix which means hotter combustion temps so very normal for temps to go up

260degF on Cylinder head temp(CHT) sensor is also normal under load, this is NOT coolant temp, its the head metal temp between cylinders 3 and 4

Dash gauge 1/2 mark is 200degF for coolant, so 215degF(above 1/2) is also normal when pulling a heavy load or going up a hill, longer uphill grade

 

Outstanding news! Thank you!