Thermistat Question

[Chad91gt]

I took out my thermistat out of my 1991 gt. Guage was showing it was over heating. I believe it's the original tstat since everything else on car is original one owner. The tstat is a 195 I believe I did a boil text and it opens only a small amount less then .. maybe 1/8 inch. Could that cause a over heating. Also a visual look at motor engine radiator there was no steaming. Or boiling over or weird noises.. im goi g to intsall a 160 tstat. Does all this sound ok?

 

[General karthief]

No, you need to put a 195 back in. Efi is temp sensitive.

 

[Mustang5L5]

Negative on the 160 stat. Fuel injection works best around 190-205 degrees. Replace with stock 195 stat.

If you are having cooling issues, don't bandaid it with a cooler tstat. Often the problem is pretty simple. Airflow, or waterflow. Look inside the radiator? If it's old, you may see gunky calcium deposits in the fins. This restricts flow and doesn't allow the coolant to cool in the radiator.

Also, check the outside fins of the radiator. Over the years, they get clogged with crap from the road. Also, how's the fan? If it's a fan clutch setup still, if you spin it by hand (engine off) does it freewheel a few times or come to a stop immediately? If it freewheels, it's junk.

Addressing these two areas, with new coolant, solves 95% of all cooling issues.

 

[Noobz347]

Just to clarify: The factory fuel injection system works best around 190-205 degrees. That's also the temperature range that oil needs to be in order to properly shed any water (among other things) it has accumulated.

Look for scale build-up inside of the radiator as well as what is mentioned above. If you find this, brace yourself for the dreaded heater-core swap as well.

 

[liljoe07]

The fuel injection system isn't really that picky about coolant temps as far as timing and fuel is concerned. There is wide range of temps where very little to nothing is changed. I'd have to get out my old computer with binary editor to post some of the tables showing this. But veryuseful.com has a few of those for viewing already. But a 160° Tstat is too cold. Seems I remember the computer needing to see temps at least 170° or the computer can go back into open loop. I'd have to check to be 100% on that though.

Now oil temps and engine wear rate based on temps has more merit.

 

[Noobz347]

a 160° Tstat is too cold. Seems I remember the computer needing to see temps at least 170° or the computer can go back into open loop.

True. What's more, it will never enter into closed loop until that 170-ish is reached.

 

[Deleted member 215073]

I thought it would go into closed loop when the O2 sensors were warmed up, and the engine temp was a minimum of 140°? Or is that mainly on OBD2 engines. I'm still learning OBD1 most of my experience is 2.

 

[liljoe07]

I thought it would go into closed loop when the O2 sensors were warmed up, and the engine temp was a minimum of 140°? Or is that mainly on OBD2 engines. I'm still learning OBD1 most of my experience is 2.

So I did some research on the old computer in Binary Editor to refresh my memory. Closed loop is on a timer. Around 60 seconds of run time, the engine can go into closed loop. Now what happens based on temps is that the Adaptive Learning will not be used until temps reach the default of 170°.

 

[mikestang63]

So I did some research on the old computer in Binary Editor to refresh my memory. Closed loop is on a timer. Around 60 seconds of run time, the engine can go into closed loop. Now what happens based on temps is that the Adaptive Learning will not be used until temps reach the default of 170°.

which is why the factory clutch fan is designed to come on at around 170. Never understood why newbs think a car running too cold is a good thing- all it does is lead to excessive sludge and premature wear.

 

[Chad91gt]

I did replace the tstat with a 180. This is before I seen most of the comments posted. I hope I didn't screw anything up. Send to run fine doesnt go above halfway point

 

[2000xp8]

It will be fine with a 180.
It's the 160 that starts to cause problems. (most of which would be more likely in the winter months unless you have a massive radiator to keep it that cool in the summer)

 

[Noobz347]

It will be fine with a 180.
It's the 160 that starts to cause problems. (most of which would be more likely in the winter months unless you have a massive radiator to keep it that cool in the summer)

Or are like me and only get the car out once or twice a year. It needs every heat soak it can get.

 

[General karthief]

Or are like me and only get the car out once or twice a year. It needs every heat soak it can get.

Quit hang'n at Disney with Mickey and Goofy and drive that thing!