Running too cool. Stuck tstat?

[Mustang5L5]

Bone stock '23 ST w 26K miles

I was alerted to this when I was programming something via ForScan, but it showed a pending DTC for a P0128. Accidentally erased it unfortunately. But decided to monitor coolant temps for a bit and noticed i run consistently 172-177 degrees. Only once did I ever see 205 degrees. But 99% of the time i'm at 175 degrees on a 95 degree humid day sitting in traffic. On cool mornings and evenings, I run about 172-174. From browsing threads, i see i should be running around the standard 200 degrees that modern EFI engine normally run at. Coolant level is good.

I keep checking my DTC's and the pending P0128 hasn't returned.

Swapping out a tstat is not a huge issue for me. I've done more involved stuff. My concern is that i'm at 26K miles and have an ESP. I'd rather a dealer take care of it for the paper trail, so that if there is an issue down the road, i don't have to argue about it. (i've had issues with past cars)

But does this align? Should I be running warmer? Is a tstat replacement the logical next step? Would you just DIY it..or should I wait and see it a DTC comes back since I have time.

BTW these P3 V3 gauges are nice for this sort of stuff.

 

[UNBROKEN]

I put it a 170° t-stat to keep mine in that range. It’s fine.

 

[2020FordRaptor]

It’s fine for the car to be running there, it’s abnormal for stock T stat but I wouldn’t worry about it.

 

[Mustang5L5]

Well, the pending P0128 hasn't returned.

I've discovered that the temp range the car drives at differs depending on if the AC is on or off.

AC off, the vehicle runs at 195-205 degrees, although it takes a little time to get up there. Runs near 205 in stop and go traffic, and 195 when driving. About where I expect it to be and what i see on all my other vehicles.

Turn the AC on, and it drops to 170's immediately. On a cool AM with the AC running it barely gets above 170 degrees, even after an hour of driving. I don't even run my modified and tuned Mustangs this cold, so it's a little concerning.

 

[Stone17]

You are fine. My ST run at 176 to 177F.

In the winter with A/C off, Sitting in traffic. Temp get to about 210F before the radiator fan kicks in.

This is from my Ford Flex. The Fan turn on at 223 with A/C off.

 

[Cruising68]

Well, the pending P0128 hasn't returned.

I've discovered that the temp range the car drives at differs depending on if the AC is on or off.

AC off, the vehicle runs at 195-205 degrees, although it takes a little time to get up there. Runs near 205 in stop and go traffic, and 195 when driving. About where I expect it to be and what i see on all my other vehicles.

Turn the AC on, and it drops to 170's immediately. On a cool AM with the AC running it barely gets above 170 degrees, even after an hour of driving. I don't even run my modified and tuned Mustangs this cold, so it's a little concerning.

I think your temps are fine. I’m in the same range when driving normal. If I start having a little fun they get around 200-205. Temp drops with AC on because the fan runs all the time when the AC is active.


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[Mustang5L5]

Thanks. That was what I was looking for. Just wanted some additional confirmation that others were seeing the same thing.