Check Engine Light On

[Joel Bell]

Fellow members,

Im getting an Engine service light and reading the error code returned (P0128 Coolant Temp below thermostat regulating temp). Has anyone else experienced this condition?



Last summer, I replaced the OEM thermostat with a Slant 180 degree version to lower the temp. Im pretty sure the OEM was 192.. so should I return to 192 because the engine is not getting hot enough now that it winter or is some other component suspect here?

 

[David Ponder]

Joel, What does the temp gague say after driving it for a while?

 

[Jerry Gerner 2]

If you wanted to take the thermostat out and test it, put it in a boiling pot of water and see if it opens. If it doesn't open there's your culprit. Just a suggestion.

 

[David Ponder]

Many new thermostats have a failsafe, (Stant "superstat" does I know) if it fails, it locks in the open mode, thus causing the engine to run too cold in winter. Happened to my daughters Taurus, and it did not throw a code, but it was in the fall so it wasnt below freezing temps.

 

[Joel Bell]

Dave,

Temp gauge never moves past less that half way..... needle does not touch white screen print.

Also, this 180 thermostat was not one of the failsafe models.



I'm thinking that maybe it's stuck open anyway.

 

[Dreman]

Had to replace mine recently. Soon after I stopped using the AC, it threw a code. I had it checked and it was "low coolant temp". The temp gage was always low, and it probably won't hurt the engine, so I went a couple of weeks like that. It actually warmed up again and I used the AC for a couple of days, and the light went out. Came back on again when it cooled down again and I stopped using AC for a couple of days. Finally changed the thermostat out (after finding my 8mm wrench!) and no problems since.

 

[EddieS'04]

No gain with a 180 anyway. go back to 192..

 

[Tom Schindler]

Last summer, I replaced the OEM thermostat with a Slant 180 degree version to lower the temp. Im pretty sure the OEM was 192.. so should I return to 192 because the engine is not getting hot enough now that it winter or is some other component suspect here?

Sounds like you already answered your question. I would go back to OEM and be done with it.





Tom

 

[Joel Bell]

Thanks to all for advice & comments.

Replaced with OEM 192 degree last night (180 was not stuck open)....

so hopefully no more ENG light.



Joel

 

[Jerry Gerner 2]

Good to hear, Ford's are tempermental with aftermarket parts, so you're better off staying with oem style parts.

:banana::supercool::driving:

 

[Bill Koonce]

Slightly off-topic:



The first mod I got for my Mustang was a Hypertech Power Programmer. This was a very basic unit that no capacity to update the tuning programs. The manual said that the programs were optimized for use with a CAI, cat-back exhaust, 93 octane fuel and a 160 degree thermostat.



You might want to use a lower temperature thermostat when it's warm again. If so, it would be a good idea to contact Torrie first about getting a tune set that works with that thermostat.

 

[scott degroot]

Unless you had a really good radiator and a good cooling fan setup I highly doubt that the engine would run colder than 160 unless it were 30 degrees or less outside. There is alot of misconception about what the thermostat actually does, alot of people think that it regulates engine temperature..this isn't totally true...it should be described as a device that limits minimum engine operating temperature...just saying

 

[EddieS'04]

Lowering the engine temp and with or without runing a performance chip. Only worked with the old speed density FI systems. Not with MAF and IAT FI motors.



edit; Im talking about. If you were looking for performance, by lowering the temp.

 

[Bill Koonce]

I agree completely, l1tech. At the time (2000) the mod motor was a big mystery to pushrod and carb guys. The Mustang boards were full of some pretty dubious ideas that assumed that making anything cooler would increase charge density...and then the magic computer would add more fuel and you'd get lots more power. I call it the Underpants Gnome Method.



IIRC at least one magazine (remember those?) did an actual test, and concluded that the then-new PI heads needed a certain amount of heat to produce full power. I kept the stock thermostat and had no problems with the Hypertech tune. I did turn the fan on sooner, but that's because I was in mostly stop and go traffic; the fan helped pull cool air over the A/C condenser while I sat in traffic.