Just curious........Why does GM put in a 195* thermostat with a coolant fan switch that turns on at 235* and off at 200*(or about)??

Other than limiting the radiator fan to just occassional use I can't figure why they didn't put in a switch to turn the fan on at 200-210* and off at 175-180* in an effort to keep the coolant at or around the 195* of the thermostat. Or, maybe they should have put in a thermostat rated at 235*.

Guess I'm lost on the answers trying to out guess GM. I run the 195* thermostat with Rodney's 210 on-200*off switch and all works great. I do notice that the fan will run a little more often when the car sits and idles than with the 235* switch. My theory is keep the car at 195* as best I can under all conditions.

Any comments....THANKS

My guess is GM got a HELL of a deal on a batch of fan switches nobody else would buy.

no kidding.........the whole thing makes no sence to me

I suspect a few reasons... being able increase the amount of time before the cooling fans kicks on (they are not needed above 35mph) will help improve MPG slightly, higher engine temps often lower tailpipe emissions, and since GM was just getting into electric cooling fans, they probably were looking to have them run as little as possible to improve service life.

I know what you mean.

When that fan turns on it is one large draw on the engine and alternator. 235* sure seems hot though. I have never owned a car that was designed to go over the thermostat speced temp...that I know of!

quote Originally posted by Kevin87FieroGT: I know what you mean. When that fan turns on it is one large draw on the engine and alternator. 235* sure seems hot though. I have never owned a car that was designed to go over the thermostat speced temp...that I know of!

All cars are designed to reach a temperature above that of the thermostat's temp. The stat temp is simply what it is designed to open at. Until it opens, it is only building pressure, not cycling coolant through the system. If your engine never got any hotter, you wouldn't need a radiator and coolant pipes. Or maybe you've only owned air cooled VWs or something?

Nope no air cooled in my past! I take that back, I have had a few air cooled lawn mowers, guess they are the same as the VW's.

So I have an S-10 with a 195* stat, but I never see the temp going over that. I assume thr stat modulates to maintain the 195* once reached. Never had run it without the stat to see what happens. I have had a bad stat that was stuck full open making it take a long time to warm the engine in the winter.

Unless coolant system is screwed up, the fan doesn't run very often. Even at lower temp switch setting, like 84 w/ AC or 87-88 L4 uses. V6 is just fine if coolant system is working right.

quote Originally posted by Kevin87FieroGT: I know what you mean. When that fan turns on it is one large draw on the engine and alternator. 235* sure seems hot though. I have never owned a car that was designed to go over the thermostat speced temp...that I know of!

You have electric fan? Many other E-fan uses switch/program above Tstat settings.

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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...)

[This message has been edited by theogre (edited 11-26-2010).]

quote Originally posted by Kevin87FieroGT: So I have an S-10 with a 195* stat, but I never see the temp going over that. I assume thr stat modulates to maintain the 195* once reached. Never had run it without the stat to see what happens. I have had a bad stat that was stuck full open making it take a long time to warm the engine in the winter.

Running without the stat will just cause it to take longer to warm up. I don't know which S-10 you have, but likely the temp gauge is not reading right for some reason. My 99 S-10 was at about 210 hot. My 04 Z71 is at about 210 hot. My Fiero is at about 220 hot. Most any stock-ish GM car made in the last 25 years is going to be around 210 hot, depending on engine and application.

Thanks guys. I have a 2000 S-10 4.3L 4x4. Never seen it above the 195 mark. No electric fan in this S-10.

It (the S-10) is taking a little longer to warm this fall, I suspect the fan clutch is locked causing the fan to run full bore keeping the engine from warming like it use to.

[This message has been edited by Kevin87FieroGT (edited 11-26-2010).]

You can run all the air through the radiator you want, if the thermostat is closed (as it should be)it doesn't matter If your engine isn't warming up as fast as it should you need to look at the thermostat.

quote Originally posted by Kevin87FieroGT: Thanks guys. I have a 2000 S-10 4.3L 4x4. Never seen it above the 195 mark. No electric fan in this S-10. It (the S-10) is taking a little longer to warm this fall, I suspect the fan clutch is locked causing the fan to run full bore keeping the engine from warming like it use to.

On the S-10, I did change the thermostat. It gets to temp, but slowly compared to last winter/spring when I changed the stat and water pump (big time blowout happened).

quote Originally posted by Kevin87FieroGT: Just curious........Why does GM put in a 195* thermostat with a coolant fan switch that turns on at 235* and off at 200*(or about)?? Other than limiting the radiator fan to just occassional use I can't figure why they didn't put in a switch to turn the fan on at 200-210* and off at 175-180* in an effort to keep the coolant at or around the 195* of the thermostat. Or, maybe they should have put in a thermostat rated at 235*. Guess I'm lost on the answers trying to out guess GM. I run the 195* thermostat with Rodney's 210 on-200*off switch and all works great. I do notice that the fan will run a little more often when the car sits and idles than with the 235* switch. My theory is keep the car at 195* as best I can under all conditions. Any comments....THANKS

So first I would think that GM does want the engine to run at 195 (ish) if possible without extra help. The engine would be running at 195 (ish) whenever you are on the highway. There is no need to have the rad fan running since more than enough air is passing through the radiator.

Now when you aren't running at speeds that will push enough air through the radiator to keep it at that temp where do you turn on the fan? Well whenever you do turn on the fan it will take energy and that energy will reduce gas mileage. Will turning on the fan early keep the engine from overheating in an extreme situation where even the fan can't keep up with the amount of heat the engine is putting out? Well if we say the we can't keep up with the fan running, turning on the fan early really is only going to help very marginally. All it would do is prevent the overheat by a little time, since we have already said the fan can't keep up with the overheat sitation. If the fan CAN keep up with the situation then the engine won't overheat.

So what temp to turn on the fan. Well at 15 psi, 50/50 antifreeze will boil at 265. So set the fan to come on 30 deg before that. That gives you enough margin to not overheat if all a sudden the load has increased. Will any engine damage occur at 235, or even 265? No. It will only occur at temps well above that. As long as you can keep the antifreeze from boiling your fine. And that is what the fan is designed to do.

The fan on my water cooled Honda Valkyrie 1500cc 6 cylinder motorcycle comes on about as often and in the same type situations as the fan in my Fiero. Neither has ever overheated as long as I have owned them.

quote Originally posted by phonedawgz: A fully open or removed thermostat would mean the engine is always being cooled by 100% of the cooling systems capacity.

Yeah, tell me about it. See Here.

Most water pump fan with a clutch "Turn on" at higher temp to...
otherwise the fan is just windmill and does use much, if any, engine power.

Test?
If clutch is working then cold clutch, fan should spin free.
Above some temp, fan will go tight on water pump shaft. See Service Man for vehicle in question.

But note... Clutch temp, not engine temp. Air Temp from Radiator gets Clutch to warm up... Clutch has its own Temp "sensor," look like a spring in front of clutch. (Some maker hide "sensor.")

------------------
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...)

[This message has been edited by theogre (edited 11-27-2010).]

As for the S-10, I think the 10 yr. old fan clutch is locked tight full time like it would be when the engine is full up to temp. Seeing how I have already changed the thermostat and have the same results as the old thermostat ( was 7 mo. old) I figure it's time for a fan clutch. I know the water pump is working great. Anyway, thanks for the great replies from all.

As for the Fiero, from what little driving I have done in the car it appears that the cooling system is working great keeping the temp at 195-200* (if I can trust the temp guage readings) 99% of the time around town and on the highway, even while at the stop lights. With the 235* switch I only had the fan come on a few times while the engine was idling for quite some time never during driving. With the 210* switch the fan never can on during driving, but did run more often during idling cycling on/ off about every 15 min. in 60* weather. I'm sure it will run more often in the warmer summer weather. As far as gas milage is concerned I can easily see the fan is a major draw on the electric and engine therefor effecting milage. There certainly is no wondering if it turned on. For now though I'm planning on leaving the 210* switch in for now and should it for some reason become annoying I'll swap back to the 235* switch.

Seems to me GM must think 195* is a good temp to run at for economy in the Fiero if that is the temp that opens the loop in the cooling system. I guess my next question would be, what exactly is the most ideal operating temp based on the engine computer, emissions, oil and whatever? Also why doesn't GM regulate engine temp to a fixed value (I know money is always an issue in design as well as reliability of a system)? Sure with any regulation the temp will float a little, but it should be easy enough to keep it in a 20* range.

Great discussion...Thanks guys!

quote most ideal operating temp based on the engine computer, emissions, oil and whatever?

define ideal.

A colder temp will give you more power to a point. Colder than that wil not. Many use 160 as that peak power point.

Better economy is achived at a higher temp. I don't know if there is a cut off point where a hotter operating temp delivers better fuel economy.

The thermostat opening temperature defines the lower range in the operating temperature. The cooling fan temperature defines the upper range.

So a 195 degree thermostat and a 235 degree fan switch, in a properly working cooling system, would maintain the engine temperature between 195-235 at ALL times.

That being said, especially with the Fiero's engine bay having less airflow than most vehicles, I don't think a 210 degree fan switch is a bad idea (it's what I run in my Fiero)

Think maybe GM had a crate full of 235* switches to use somewhere?

How about this, does the 2.5L also use the 235* switch? And any chance they put it in the 2.8L soley for ecomony on the line?

The ECM must be setup on some sort of datum number to work off of. Guess that number would be a good one to shoot for.

quote Originally posted by Kevin87FieroGT: Think maybe GM had a crate full of 235* switches to use somewhere?

370,168 Fieros were produced. That's more than a crate of swtiches

quote How about this, does the 2.5L also use the 235* switch?

Yes it does

quote And any chance they put it in the 2.8L soley for ecomony on the line?

Considering the engines weren't built on the same line that doesn't make any sense

quote The ECM must be setup on some sort of datum number to work off of. Guess that number would be a good one to shoot for.

Huh?

[This message has been edited by phonedawgz (edited 11-28-2010).]

Two crates, one here one there.

Forget the datum thing....it really doesn't matter.

[This message has been edited by Kevin87FieroGT (edited 11-28-2010).]

A 180 stat and 195-210 fan switch should keep you in the generally optimum range for power and effeciency on the 2.8.

Dobey, that appears to be the answer. As the fan rarely operates going down the road the fuel loss of it turning on while idling is minimal (just my thought). What are you running in yours?

I have a 160 stat in my 2.8 right now, and the stock fan switch. But it's getting replaced with an LS4 soon enough, and that will have a 180 stat, Champion 3-core aluminum radiator, and tuned to bring the fan on around 200.

How hot does yours get in mid summer driving around town?

quote Originally posted by dobey: A 180 stat and 195-210 fan switch should keep you in the generally optimum range for power and effeciency on the 2.8.

There is no optimun range for power AND effeciency. One or the other. Not both.

I would like to think GM had the best combination Stat/Fan switch after all their proving ground runs, but after seeing all the problems guys have high temps in the engine compartments and GM adding a cooling system for the alternator and coil it sort of makes you wonder. Although they did remove the engine fan system in 88. Also the 80's thought process (and todays as well) is not to build a car to last 25 years. So it goes.

Certainly was a lot of compromise built into to these cars, as I'm sure there is in any vehicle.

I have seen a lot of people on here who 1 - state their radiator fan doesn't work and have to 'fix' something and 2 - are totally concerned that their temp gauge moves close to the red and think something needs to be repaired.

The real MAJOR actual cooling problem is air in the system.

GM's problem is that they did not account for subpar aftermarket water pumps, improper coolant bleeding procedures, incorrect radiator cap listings at auto parts houses, and semi-crushed coolant pipes. They also did not account for people removing all of the heat shielding inside of the engine bay for better access. IMO these two things are the culprit for most heat-related problems.

that being said...again...the engine was designed to run at 195 degrees, not hotter than 195, and a lower-temp fan switch is not going to noticably hurt fuel economy. A 180 degree or 160 degree thermostat, however, is a bad idea IMO.

[This message has been edited by masospaghetti (edited 11-28-2010).]

Certainly is no shortage on emphasis on servicing the cooling system correctly when changing the fliud.

quote Originally posted by masospaghetti: that being said...again...the engine was designed to run at 195 degrees, not hotter than 195, and a lower-temp fan switch is not going to noticably hurt fuel economy.

So if this is the case, what are the gains achived by running a lower temp cooling fan. You already said it will reduce fuel economy.

quote Originally posted by masospaghetti: The thermostat opening temperature defines the lower range in the operating temperature. The cooling fan temperature defines the upper range. So a 195 degree thermostat and a 235 degree fan switch, in a properly working cooling system, would maintain the engine temperature between 195-235 at ALL times. That being said, especially with the Fiero's engine bay having less airflow than most vehicles, I don't think a 210 degree fan switch is a bad idea (it's what I run in my Fiero)

This guy gets it.

Both of my C4 Corvettes also used 195* stats and 235* fan switches. So they prob just threw in what was already on the shelf from the factory. The fans only came on in traffic or with A/C on....never on the highway.

I changed both of them to 160* stats and 210* fan switches just because I believe in cooler running engines last longer...(JMO)

quote Originally posted by rogergarrison: I changed both of them to 160* stats and 210* fan switches just because I believe in cooler running engines last longer...(JMO)

You want engine to last? Oil temp and condition matter more than Coolant temp.

What Oil temp measure? What? You didn't measure Oil Temp Max and Oil temp warm-up time? Most people don't...

Oil Temp is more important then Coolant Temp.... Low Coolant temp likely mean low Oil Temp and takes longer to get to normal oil Temp. Oil needs some heat to work right.

Low oil temp mean you Can't dry out gas, moisture, etc, fast enough.
Gas? All engine has some Blow By. (Why you need a PCV too.)

------------------
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...)

As for oil temp, 195 coolant temp would be the same as the block temp (with the exception of the inner cylinders) and probably very close to the oil temp.

Looks like food for another thread.

Great info and conversation guys, it all gets you thinking what's best for "MY" Fiero.

Here's a question. With the fan switch you have, does your fan run while driving down the road in summer temps. with the a/c off??

quote Originally posted by phonedawgz: So if this is the case, what are the gains achived by running a lower temp cooling fan. You already said it will reduce fuel economy.

Yeah, it will increase electrical draw since the fan is operating more. But enough to make a measurable difference? I doubt it. And an engine at 195 degrees will radiate less heat than one a 235 leading to a cooler engine bay. Which, IMO, isn't a bad thing with 25 year old electronics and plastics around.

quote Originally posted by masospaghetti: The thermostat opening temperature defines the lower range in the operating temperature. The cooling fan temperature defines the upper range. So a 195 degree thermostat and a 235 degree fan switch, in a properly working cooling system, would maintain the engine temperature between 195-235 at ALL times.

As previously mentioned, there is nothing mysterious about the reasoning for the two different temps. 195 -235 is the designed operating range, end of story. If you want to wear out your electric fan quicker, as well as further strain the alternator, relay and battery than there is no harm in having it come on earlier. There is also no harm in letting the water temp stay at 234 either. A 40 degree operating range for a vehicle designed to work in Alaska as well as it works in south Florida is a pretty narrow range. There was no reason to narrow it further to 15 degrees (195-210) as there is no advantage in doing so, and there are disadvantages listed above. A thermostat simply allows water to pass at a minimum temperature. Once it is open, it can not control how hot the engine gets. Not having a thermostat can also sometimes allow the coolant to flow through the radiator fast enough that it does not have enough time in the radiator to dissipate heat through the fins making the vehicle overheat quicker.

quote As for oil temp, 195 coolant temp would be the same as the block temp (with the exception of the inner cylinders) and probably very close to the oil temp.

Not necessarily. There are no coolant passages below the cylinder walls and there is very little oil above the cylinders. The temperature difference between water and oil can be significant. Before I got my track car sorted out I would have water temps at 230 and oil temps at 280+ (very bad). Now my water temp stays between 190-200 and oil temps are between 230 and 240.

I don't know about you, being in Florida; but I don't plan to drive my Fiero to Alaska. Ever.

I'll second that. It would be tuff to get in the car with all the snow gear on.

SCCAFiero: Many good points on the fan and alternator, relay and battery wear.

[This message has been edited by Kevin87FieroGT (edited 11-29-2010).]