Thermostat will cycle when idle but will not cycle if the AC is on or while driving. When driving or when AC on temps are between 204 and 210. I have heat at all times after engine is warm. Here is what I have done so far.

Replaced water pump (Was before I bought it)
Replace tee valve seals (From Ford)
replace thermostat (From Ford)
Flushed whole system (nothing clogged)
No leaks present
replaced thermostat seal just incase

While idle and parked fans come on at 213.8, at 215 thermostat opens temps drop to around 204 then fans turn off.
While idle with heat on same thing.

Turn on ac, fans come on coolant temp goes to 208.4 and stays there. System will not cycle nor overheat.

While driving same as when ac on.. system will not cycle or overheat.

Temp sensor is being logged through torque

Any help Is appreciated

 

WAD (Working As Designed).

NOT WAD... Thermostat should open at ~195°F.

Is the thermostat a Motorcraft part? hint: All of the aftermarket offerings tend to be problematic.

WAD
.

 

I have the 5.0 not sure if there is a difference.

Yes it does say motorcraft on the thermostat.

I keep thinking it's getting stuck partially open and allowing seeping of coolant?

 

Macht nichts... All of the cooling systems have the same parameters.

OR... Air in the system... hint: Helps to have the front of the vehicle raised a bit.

 

I'm pretty sure the air is out of the system at this point. I have done the front elevation trick right out of the gate upon filling. On my truck if you don't you will for sure have an air pocket stuck in the heater core.

Also... my temps are never below 203 at idle and when driving never obove 208.8 or atleast that's what torque is telling me.

I feel like I'm losing my mind... Is this running normal??

seems weird to me that when parked at idle I see a very high threshold before the thermostat opens. Then it goes back down to 204. When driving it seems to stick between 204 and 208. This makes me feel like the thermostat is not opening.

 

Verify a thermostat by heating in a pan of water along with a thermometer.

 

Thanks Barry,
that was exactly my thought and I did it this morning. I also have a generic thermostat made by motorrad.. so I did them both at the same time. The motorrad opened up at about 202 and the Motorcraft opened up at about 212. So I put the motorrad in just to see what would happen. Still fighting the rain to get all the air out of the system 🙄. Gotta love FL in the summer....

 

With the generic thermostat I'm now overheating.
I'm pretty sure I have a partially clogged radiator at this point. The generic thermostat does not have the recirculating holes like the Motorcraft had. Not allowing as much circulating water From the Block back into the pump. While doing my testing I noticed that the driver side radiator fan was barely blowing any hot air. I checked the passenger side and while it was warm the heater core in the truck was blowing hotter air....

Once I get everything taken apart again and get the radiator out I will follow up.

Thank you guys for chiming in and giving me a place to talk this out!

 

I don’t think you are overheating, seems to me your temps are fine. When I tried to use and aftermarket thermostat my temps hit 230 and were still climbing with fans on high. Now when the fans come on you aren’t cooling back down then I would be concerned.

Also, Coolant temps should be dropping across the radiator from the top inlet to the bottom outlet.

 

The radiator did have poor flow but I don't think it was enough to impede the cooling so bad to cause the 225 and climbing temperatures. While everything's apart I'm going to go ahead and pull the pump off and take a look at it. Perhaps the previous owner didn't really replace the pump as they told me??

Anyone know what the oem pump is rated for milage wise?