Received my new aluminum radiator just waiting for the new hoses to arrive.
My question is: Which thermostat would be better for summer time usage ONLY?? I'm thinking the 180 degree, but this group would know better than me.
Also, I keep reading about the radiator fan module switch -- can anyone tell me where that is located? Is it near or on the radiator or the engine?

Stock Fiero? Stock thermostat: 195*

Fieros are not designed to overheat in stock form. A 180* thermostat will open sooner, just making the coolant take longer to reach it's stable temp. However, a cooler thermostat will not do anything to limit the stable temperature if it is above 180*F or prevent over heating. The stock ECM in the Fiero expects the car operate in the stock temp range. If you are running too hot, figure out what is causing it.

Condition of coolant pipes
Condition of radiator
Condition of water pump
Condition of radiator fan

When the Fiero was new it could sit all day in traffic in Phoenix and not over heat.

The radiator fan is controlled by the HVAC (on with A/C) and by a switch in the lower intake manifold near the thermostat housing.

[This message has been edited by carbon (edited 05-29-2013).]

quote Originally posted by carbon: Stock Fiero? Stock thermostat: 195* Fieros are not designed to overheat in stock form. ... a cooler thermostat will not do anything to ... prevent over heating. The stock ECM in the Fiero expects the car operate in the stock temp range. If you are running too hot, figure out what is causing it.

I agree on all counts. I have always run a 195 degree thermostat in my 3.1 V6 Fiero with A/C and OEM radiator, and I have never experienced overheating ... even on 100+ degree days. I do run one of Rodney Dickman's 210 degree fan switches, but that's just me.

Ideally you want the engine to run at a small temperature range around operating temp. You don't want large swings in engine temperature based on driving conditions.

The thermostat controls the minimum operating temperature of the engine and the fan switch controls the maximum operating temperature. Think about it: The coolant will never get colder than the thermostat temperature because the thermostat will close, removing any ability for the radiator to remove heat. Also, when the fan switch temperature is reached, the engine has max cooling and (if the cooling system is working properly) the coolant will never get hotter.

By setting your thermostat to 180 F, you've just increased the operating range to 180-236 F (236 F being the stock fan switch temperature). That's a pretty big swing and not great for consistent engine performance.

Ideally, run a 195 F thermostat with a 210 F fan switch to keep the engine in a narrow range of operation. The stock 236 F switch is too high, IMO, and doesn't provide much margin for error if you have a slightly weak coolant mix or another cooling system component that isn't operating 100%. At normal cooling system pressures, coolant boils at about 260 F - once it starts to boil, you rapidly lose ability to remove heat.

If you have overheat problem w/ 195 Tstat then has major cooling problems, like Crush pipe(s), plugged rad, etc.

See my Cave, Thermostat etc.

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Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)

The Ogre's Fiero Cave (It's also at the top and bottom of every forum page...)

quote Originally posted by masospaghetti: Think about it: The coolant will never get colder than the thermostat temperature because the thermostat will close, removing any ability for the radiator to remove heat. Also, when the fan switch temperature is reached, the engine has max cooling and (if the cooling system is working properly) the coolant will never get hotter.

This completely ignores the fact that there is a heater core in the system which is very capable of reducing the coolant temp even when the thermostat is closed. May not make the passengers in the car comfortable, but the heater core is one of the factors that comes into play in the complete cooling system.

The stat doesn't set the max, it sets the minimum. As said, it will still swing upward (normal.) I run the hottest stat I can. If I could find a 205 I would run that but you have to have a good cooling system.

quote Originally posted by masospaghetti: Ideally you want the engine to run at a small temperature range around operating temp. You don't want large swings in engine temperature based on driving conditions. ... The thermostat controls the minimum operating temperature of the engine and the fan switch controls the maximum operating temperature. ... Ideally, run a 195 F thermostat with a 210 F fan switch to keep the engine in a narrow range of operation.

I agree completely.