Puzzled by 2003 F100 overheating

[Alsioncaseyb]

I am at a loss. New water pump impeller as I had to replace the lower unit seals. Nothing different. This is probably the 4th time I have changed the impeller. We get into a lot of mud so I inspect and change it often .Ran fine the next day til i slowed down to an idle. Hot engine alarm went off. Got home and changed the thermostat. It was in bad shape, not really corroded but the rubber seal was completely gone. Replaced. Couldn’t really see any corrosion. Still overheating. I am getting good flow from thermostat. Getting flow at pressure relief valve(also replaced). Good flow from where temp sensor is located. I did notice the motor runs rough when the temp sensor is plugged in and runs smooth when unplugged. Should it do that and can the sensor be my issue?

[fairdeal]

hmmm.
I'm weak - very weak - on antique/carbureted engines..

But if you have an ohm meter, a thermometer,
and a means to heat water,
you can check the functionality of that thermosensor

[99yam40]

does it make you wonder why they say to measure voltage and then give Ohm readings?

[Alsioncaseyb]

I am going to try and replace it. I hate throwing parts at it but every normal thing that would cause this is new. I just find it odd that it idles rough when I have the sensor plugged in but when I unplug it, the motor runs smooth. I am on vacation with it and don’t have a volt meter and don’t want to buy one for the same price of a new sensor since I have a good one at home.

[zenoahphobic]

does it make you wonder why they say to measure voltage and then give Ohm readings?

They keep you on your toes (manual writers)!
When they say measure output voltage they are assuming that you are measuring the thermostat in circuit and not disconnecting it - then it would be voltage but they omitted what those voltages in respect to both those wires would be (in circuit)! Maybe another person (editor) realised the difficulty in measuring the thermostat’s temperature in situ. After all you can’t have resistance without a current, and then you can’t have any current without some voltage. All fun.