Depending on what switch you have in the car, I believe the stock temp sensor was 235 F. But how accurate is the gauge in the car? My 87 GT gauge reads well below 200 while running on the high way, but will creep up past 220 before the fan kicks on.
Thank you. I guess I need to drive it to see if it kicks on.
My experience with several Fieros is that the fan rarely if ever normally kicks on with the factory fan switch.
Just for peace of mind, on every Fiero I've owned, I've installed Rodney's 210° on and 200° off Fiero Low Temp Radiator Fan Switches, while retaining the stock 195° thermostat. Works perfect.
[This message has been edited by Patrick (edited 03-16-2015).]
Thank you. I guess I need to drive it to see if it kicks on.
The fan will likely not come on under normal driving and if it did, you probably wouldn't know it. But do take it for a drive then bring it back and leave it running. Open the hood and watch for the fan to kick on then check the gauge to see what temp it's indicating. Like Old Lar's, my 87 also runs below 200 with a 195 thermostat.
If your gauge needle hasn't slipped, it should move up to 100 when you first turn the ignition on without starting and the engine cold (around 70 degrees ambient temp).
My experience with several Fieros is that the fan rarely if ever normally kicks on with the factory fan switch.
Just for peace of mind, on every Fiero I've owned, I've installed Rodney's 210° on and 200° off Fiero Low Temp Radiator Fan Switches, while retaining the stock 195° thermostat. Works perfect.
Agreed. Change to a lower temp switch. I'm running them on both my cars.
SW500 close 220-240 (Standard TS82) SW505 close 213-229 (Standard TS85) SW555 close 210 open 205
The SW555 ("Rodney's") *seems* excessive for a stock motor in a normal climate. I'd personally use the SW505 on an iron block/iron head motor to help keep emissions down and economy up, except maybe in a super-hot area.
Because there is no reason to run an automobile engine that cool, especially a big lump of iron that can take the heat. Higher temperatures result in better combustion, lower emissions, and better economy. You really want to keep the engine between 205 and 215 degrees (+/-) Rodney's fan switch will necessarily keep the engine at or below 205 degrees, which is sub-optimal.
Because there is no reason to run an automobile engine that cool...
???
As previously stated, the stock thermostat is 195°. I suspect that's the actual temperature that GM wanted these engines to run at. Neither one of us is suggesting that the stock thermostat should be swapped out and replaced with a 180° or 160° one.
I think you misunderstand the relationship of the thermostat and the fan switch. The thermostat is the MINIMUM temp an engine should operate at. The thermostat stays closed, keeping coolant circulating inside the engine, until a minimum temperature is reached. At that point, the thermostat begins to open and allows coolant to circulate through the radiator, bleeding off heat at a less than 1:1 relationship (the engine produces more heat than the radiator can bleed standing still). I don't know at what temperature the stock thermostat is fully open, but it's obviously greater than 195 degrees. The rated temperature of a thermostat is when it *starts* to open.
The fan switch is the MAXIMUM temperature the engine should operate at. Stock, that's about 235 degrees. At that point, the radiator fan switches on and accelerates the rate at which the radiator bleeds off heat. Somewhere in the middle - between 195 degrees and 235 degrees - is where the engine will spend most of its time, given average airflow from average speeds. In the middle is about 215 degrees, where the engine has a good mix of fuel economy, mechanical safety, and low emissions. If GM wanted the engine to run cooler, they would have installed a larger radiator that could bleed off heat faster and/or a lower temp fan switch to assist sooner or a thermostat with a colder rating. There is no magic in designing cooling systems, the Fiero doesn't do what it does by accident. They didn't lower the operating temperature because running an iron block+head engine at 195 degrees would be terrible for emissions and less than ideal for economy.
Rodney's fan switch is just a fan switch from a 3.8 turbo (IIRC), not some magic switch he made. Boosted cars are at increased risk of detonation compared to naturally aspirated cars and keeping the engine cooler is a must to avoid knock. That fan switch exists to address a totally different environment, not to keep a 140hp lump of iron at under 200 degrees. There is zero point in doing that. There is a reasonable chance that running the engine that cool will result in a thermostat that either never fully opens, or is continuously opening and closing. If you're going to run a 200 degree fan switch, you should be running a 180 degree thermostat, maybe even a 170 degree. The turbos ran a 180 degree.
It would seem then from what you're saying that as soon as the car starts moving forward (and air is pushed through the rad without any need for the fan to be switched on), that the coolant temp would drop below what you're suggesting is required to maintain the "ideal" engine operating temperature.
When any of my Fieros are being driven, even on hot summer days, Rodney's "excessive" 210° on and 200° off fan switch never turns the fan on while the car is moving. Please explain how this switch contributes to lowering the operating temperature of my engine when it doesn't even do anything while the car is actually being driven?
Granted, I'm no mechanical engineer... but I find what you're stating very difficult to agree with.
I'd like to hear some other opinions on this. Could be interesting.
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Originally posted by thesameguy:
Rodney's fan switch is just a fan switch from a 3.8 turbo (IIRC), not some magic switch he made.
I enjoy the discussion, but no need to get catty... okay?
[This message has been edited by Patrick (edited 03-18-2015).]
Originally posted by Patrick: It would seem then from what you're saying that as soon as the car starts moving forward (and air is pushed through the rad without any need for the fan to be switched on), that the coolant temp would drop below what you're suggesting is required to maintain the "ideal" engine operating temperature.
When any of my Fieros are being driven, even on hot summer days, Rodney's "excessive" 210° on and 200° off fan switch never turns the fan on while the car is moving. Please explain how this switch contributes to lowering the operating temperature of my engine when it doesn't even do anything while the car is actually being driven?
This is one of the benefits of the active shutter systems that some new cars have, for fuel economy. When starting cold, the shutters are closed, which prevents air flowing through the radiator, so it helps the system to reach operating temperature a little faster than without a closed shutter.
Do you have a 195 degree stat in your car? What is a "hot summer day" for you exactly? Is your temp gauge reading accurately? What temp does your gauge show on those days? If a 210 fan switch never turns the fan on, on a hot summer day, then I'd think maybe something is not quite right somewhere; or a "hot summer day" is not very hot.
Theres the idea that hotter engines (to a point) are more efficient. But each model of engine probably has its happy spot. I did put the 200/210 switch in my cars, one 2.5 and one 2.8 but it probably wasnt needed. Its just unnerving to see the guage get up so high when the factory one is in there. The engines other fluids react to the heat too, is something to think about.
But also I had a 1990 grand am with the Iron Duke that had apparently had a stuck thermostat for 5 years and it ran at about 120 on the gauge, never had a problem, the heater was a tad weak tho The good thing especially with older cars is the margin for error seems pretty large.
[This message has been edited by 2.5 (edited 03-18-2015).]
It would seem then from what you're saying that as soon as the car starts moving forward (and air is pushed through the rad without any need for the fan to be switched on), that the coolant temp would drop below what you're suggesting is required to maintain the "ideal" engine operating temperature.
I don't know how you got that from what I said. With the car not moving and no cooling fan, it will eventually overheat regardless of what the thermostat is. The radiator is not capable of maintaining any temperature indefinitely - it bleeds off heat than the engine produces. Some amount of airflow is needed to maintain equilibrium in the system. When stationary, that's a fan. When moving, it's airflow. How much heat either of these will help eliminate is a function of speed and to some degree of ambient temperatures. It's not possible to maintain a perfect temperature at all times in all conditions - there are necessarily some variances.
Broadly, I'm with Dobey - if your 210 degree switch never turns on your fan on a hot summer day, something unexpected is happening. 210 to 220 F is where GM designed the 2.8 to operate. If yours isn't getting there, it's running cold. (Side note: 210 to 220 is where GM designed *most* of their all-iron motors to operate, from the 2.8 to the 7.4). My Fiero, 350-powered Suburban, and 454-powered motorhome all run at about 215 degrees on the freeway on a warm (not even hot) day, right in the middle of the gauge.
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Granted, I'm no mechanical engineer... but I find what you're stating very difficult to agree with.
You're entitled to agree or disagree as you see fit, of course. All I have put forward is how thermostats work, the relationship between thermostats and fan switches, and factual information about target operating temps for the V6. All of this information is readily available from a variety of sources.
(Side note: 210 to 220 is where GM designed *most* of their all-iron motors to operate, from the 2.8 to the 7.4). My Fiero, 350-powered Suburban, and 454-powered motorhome all run at about 215 degrees on the freeway on a warm (not even hot) day, right in the middle of the gauge. .
This suprises me as my many GM Iron block vehicles ran about 200-205. But maybe thats just gauge variance. But they all would turn the fan on eventually if you sat in traffic or let it idle in your driveway.
I stated at least twice in this thread that I run the stock 195° thermostat. It's a Stant SuperStat.
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Originally posted by dobey:
If a 210 fan switch never turns the fan on, on a hot summer day, then I'd think maybe something is not quite right somewhere; or a "hot summer day" is not very hot.
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Originally posted by thesameguy:
Broadly, I'm with Dobey - if your 210 degree switch never turns on your fan on a hot summer day, something unexpected is happening.
Guys... please read what I actually posted. I did not say that the fan switch never turns the fan on ever. The fan is obviously turned on eventually while the car is sitting still with the engine running.
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Originally posted by Patrick:
When any of my Fieros are being driven, even on hot summer days, Rodney's "excessive" 210° on and 200° off fan switch never turns the fan on while the car is moving.
Please explain how this switch contributes to lowering the operating temperature of my engine when it doesn't even do anything while the car is actually being driven?
I'd still like to see that last question addressed.
I'd still like to see that last question addressed.
There are a lot of possible explanations, including but not limited to:
1. It's almost impossible to tell if the cooling fan turns on while the car is moving, so maybe you just don't reliably notice it 2. The fan switch could be imperfectly calibrated 3. Your gauge could be imperfectly calibrated 4. Your hot is not that hot 5. Moving at 5mph is not the same as moving at 70mph 6. You drive like grandma
The points are these:
1. If the thermostat starts opening at 195 degrees and the fan switch cools the system to 200 degrees there is a high likelihood the fan is cooling the engine to the point the thermostat starts to close again. This is undesirable. 2. The engine was designed to optimally operate at 210 to 220 degree. Sometimes it may run cooler, sometimes it may run hotter, but in that range is where GM specifies this engine to run. It is specified in the shop manual. Note the location of 220 degrees on the temp gauge. If you are actively prohibiting your engine from running in this range, you are actively compromising fuel economy and emissions. 3. Maybe on an average day at an average speed your engine reaches 209 degrees and sits there perfectly, never triggering the fan switch. That's a variance you have to accept on ICEs. But taking that last degree and then sapping 10 degrees and putting the thermostat back to work is silly. It's extra work on the thermostat, extra work on the cooling fan, and an adverse affect on economy and emissions. 4. If GM wanted the engine to run at 195 degrees they would have put on a 180 degree thermostat and a 210 degree fan switch just like the GNXs. They didn't, because they didn't.
1. It's almost impossible to tell if the cooling fan turns on while the car is moving, so maybe you just don't reliably notice it 2. The fan switch could be imperfectly calibrated 3. Your gauge could be imperfectly calibrated 4. Your hot is not that hot 5. Moving at 5mph is not the same as moving at 70mph 6. You drive like grandma
1. If the fan was running while I was cruising down the freeway on a hot summer day, I would hear it still running when I came to a stop. I don't hear it running, but I can hear it come on a few minutes after sitting still. 2. Not possible... it's a "magic" switch made by Rodney. 3. That makes no difference as to when the fan comes on. 4. Although I live in the land of snow and igloos, it can get into the 90's here on the coast. 5. Do you often drive at 5mph? I don't. It would be interesting to know though at what minimum speed the airflow (through the rad, through the engine bay, etc) is as effective for cooling as having the fan blow just through the rad. I suspect the minimum speed required isn't all that fast. 6. I assure you I don't.
I also want to make it clear that my experience has not been limited to one Fiero. I've driven (and still own) an '84 duke, an '86 GT, and an '88 Formula. They have all behaved in a similar manner with the swapping out to the fan switch being discussed.
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Originally posted by thesameguy:
They didn't, because they didn't.
Well, I guess that settles that!
[This message has been edited by Patrick (edited 03-18-2015).]
"Into the '90s" isn't hot. Let me know when it hits 115. If you're going 45mph in cool/cold weather all the time, I wouldn't expect the engine temps to get much over 210 - mine don't until late spring or early summer. In actually hot weather, or creeping around in traffic at 5mph you'll see it quite often. There is some variance, the system has tolerance necessarily. And the system can and is designed to take it. All you're doing with that fan switch is overcooling the engine. Seriously. Maybe in Mojave there would be a reason to use it to delay or avoid reaching that point where the system can't adequately shed heat, but in BC there certainly is not. You do what you want of course, but "run the engine colder" is old hot rodder myth, like "engines need backpressure" and "run avgas for the best performance."
All you're doing with that fan switch is overcooling the engine. Seriously.
Ultimately, it does not matter to use the lower temp fan switch you want to argue about. As you pointed out, it is the thermostat that controls engine temp.
The fan could be rigged to run ALL the time without harm - but that's unnecessary and a big electrical load. It just needs to cool the coolant in the radiator to ready it for the engine when the thermostat opens. The coolant only needs to be at or lower than the normal engine operating temperature of 195F.
With the stock 235F fan switch and the car standing still, once the engine gets to 195F the thermostat will open and stay open as the entire cooling system (including coolant in the radiator) eventually heats up to 235F when the radiator fan FINALLY comes on to cool the entire open system.
Meanwhile, the engine temperature certainly has not been regulated to 195F as intended (because it got to 235F). All a lower temp fan switch does is get that fan on sooner to cool the radiator coolant.
It would have made more sense to have the temp switch on the radiator outlet to ensure than coolant is at or just below normal engine operating temperature of 195F (you can't cool the engine with HOT water).
Ultimately, it does not matter to use the lower temp fan switch you want to argue about. As you pointed out, it is the thermostat that controls engine temp.
"Into the '90s" isn't hot. Let me know when it hits 115.
So is it necessary then to be driving in 115° weather before the engine reaches its "ideal" operating temperature? That seems rather unlikely.
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Originally posted by thesameguy:
You do what you want of course, but "run the engine colder" is old hot rodder myth...
No one in this thread has suggested to "run the engine colder" than what the factory recommends... which as far as I know is 195°. You appear to want to run the engine hotter. That's your choice as well, but not one that appears to be shared by others here.
I appreciate your input on this (I really do), but I think we disagree on the basics of what the proper 2.5/2.8 operating temperature is supposed to be, and the best way of maintaining it.
I'm sorry, but that is obviously not correct. The thermostat controls only MINIMUM temperature, not maximum. The fan controls MAXIMUM engine temperature. The thermostat's only job is to help the engine reach operating temp faster. Whether you install a 180 degree, 195 degree, or no thermostat whatsoever the engine will ultimately reach the same temperature, limited only by airflow or the fan. The size of the radiator - its ability to shed heat - is what sets the average engine temperature given average conditions. This is engine cooling system 101.
Thermostats have a “rated” temperature such as 180F or 195F. This is the temperature the thermostat will start to open, give or take 3 degrees. The thermostat fully open about 15-20 degrees above its rated temperature.
If you are running a 195 degree thermostat and a 210 degree fan switch, you are probably turning the fan on before the thermostat fully opens. You are then cooling the system to the point the thermostat is mostly closed. As I keep saying, a 210 degree fan switch on a 195 thermostat is wasting the fan, overusing the thermostat, losing economy, and increasing emissions.
You guys believe whatever you want, but actual science suggests you're doing it wrong.
Originally posted by Patrick:So is it necessary then to be driving in 115° weather before the engine reaches its "ideal" operating temperature? That seems rather unlikely.
Again, I don't know how you got that from what I said. It's impractical to design a system that keeps a specific temperature at all times given varying speeds, load, and ambient temperatures compromises and tolerances are built into the system to account for that. The Fiero has to work in BC and it has to work in Mojave. In BC, it's more likely to run on the cool side. In Mojave, it's more likely to run on the warm side. On the wide open freeway, it's more likely to run on the cool side, in traffic, more likely to run on the warm side. You're "my fan never comes on" is because you are driving "more quickly" in "cooler" weather. I have the same experience here. You would find driving "less quickly" in "warmer" weather your fan would spend a great deal of time on. These are the necessary tolerances built into the system.
Really, I don't care. Run avgas, build for back pressure, run no thermostat at all, change your oil every 3,000 miles. Whatever helps you sleep at night.
Weird in testing thermostats seem to open up quick.
Cheap ones or broken ones will. They are not designed to do that. Or maybe you don't have very good control over the testing temperature. Putting a 195 degree thermostat in 210 degree water will cause it to pop right open. Put it in 196 degree water and it will just crack open. You probably understand the limitations of controlling the temperature of a pot of water on a stove.
I'm sorry, but that is obviously not correct. The thermostat controls only MINIMUM temperature, not maximum. The fan controls MAXIMUM engine temperature. The thermostat's only job is to help the engine reach operating temp faster.
This makes sense. It doesnt really change the point of installing a lower temp fan switch, which is to keep the temp from getting as high. 210 instead of 235.
[This message has been edited by 2.5 (edited 03-19-2015).]
Really, I don't care. Run avgas, build for back pressure, run no thermostat at all, change your oil every 3,000 miles. Whatever helps you sleep at night.
The discussion has now unfortunately deteriorated...
This makes sense. Though the thermostat also lwets in the cooler water to cool the engine back down as well, which comes from the rad/fan.
It doesnt really change the point of installing a lower temp fan switch, which is to keep the temp from getting as high. 210 instead of 235.
I agree the 235 is probably excessive. I'm sure GM ran the numbers and the cost of dealing with rare head gasket failures as a result of "high" temperatures was dwarfed by the costs of people wearing out fans, or something like that. 235 degrees is not a problem for an iron block + iron head motor. The 2.8 can probably run to 250 degrees before it's *actually* a problem.
The reason I installed a lower temp fan switch is in the summer here in evening commute traffic my cooling system gets heat soaked and it's difficult for it to shed heat. There were several times at 235 degrees with fan on that the temperature would still climb a few more degrees before the system could catch up and start shedding. By lowering the fan switch to 213-229 (its imprecise), the fan comes on before the system is heat soaked. Now the car will creep up to 220 or 225, the fans come on and take me back down to 210 or 215 and I avoid the scary "235 and still climbing" scenarios. It's only a problem 2-3 months out of the year - the other months the stock fan switch has not been a problem. (Which I think is fairly obvious - how many Fieros were sold? How many "upgraded" fan switches? How many have premature cooling system failures? My car is 30 years old, from the SF Bay area, and has been rockin' a factory fan switch until last summer!)
The discussion has now unfortunately deteriorated...
You are clearly not interested in understanding how cooling systems work, and/or totally committed to running a 210 degree fan switch. It's your prerogative, but your line of reasoning is the exact same hot rodder legends that spawned those other myths. Whether you don't understand what I'm saying, don't want to, or don't believe me is really not my concern. I laid out the facts, what you do with them is up to you. I really don't have any further interest in repeating myself is all.
Originally posted by thesameguy: I agree the 235 is probably excessive. I'm sure GM ran the numbers and the cost of dealing with rare head gasket failures as a result of "high" temperatures was dwarfed by the costs of people wearing out fans, or something like that. 235 degrees is not a problem for an iron block + iron head motor. The 2.8 can probably run to 250 degrees before it's *actually* a problem.
The reason I installed a lower temp fan switch is in the summer here in evening commute traffic my cooling system gets heat soaked and it's difficult for it to shed heat. There were several times at 235 degrees with fan on that the temperature would still climb a few more degrees before the system could catch up and start shedding. By lowering the fan switch to 213-229 (its imprecise), the fan comes on before the system is heat soaked. Now the car will creep up to 220 or 225, the fans come on and take me back down to 210 or 215 and I avoid the scary "235 and still climbing" scenarios. It's only a problem 2-3 months out of the year - the other months the stock fan switch has not been a problem. (Which I think is fairly obvious - how many Fieros were sold? How many "upgraded" fan switches? How many have premature cooling system failures? My car is 30 years old, from the SF Bay area, and has been rockin' a factory fan switch until last summer!)
So what is your fan switch technically called in degrees on/off? Yep you run one for the same reasons I do, its just that it doesnt get as hot as often here and Rodneys switches were available and had a good track record of uses by others
Whether you don't understand what I'm saying, don't want to, or don't believe me is really not my concern. I laid out the facts, what you do with them is up to you. I really don't have any further interest in repeating myself is all.
The purpose of a forum is to discuss differing opinions. There's no need to convince anyone of anything. If you don't wish to "repeat" yourself, then don't... and leave it at that.
[This message has been edited by Patrick (edited 03-19-2015).]
So what is your fan switch technically called in degrees on/off? Yep you run one for the same reasons I do, its just that it doesnt get as hot as often here and Rodneys switches were available and had a good track record of uses by others
It's the Wells SW505 or Standard Motor Products TS85. The on (closed) temperature is about 229 degrees, and the off (open) is about 213 degrees. In practice, mine comes on around 225 and turns off again around 210, as indicated by the ECM sensor read by Tuner RT. +/- 4 degrees is a fair tolerance. The SW505 is from an early '80s 2.8 V6 (I assume it's a lower temperature to account for a carb'd motor - carb'd motors are less tolerant of extreme heat than fuel injected ones). I have never actually seen one, but I'm pretty sure Rodney's switch is a Wells SW555 as the specs match. It's from a late '80s 3.8 turbo, either a GN or a Firebird turbo. It is AFAIK the coldest one-wire fan switch that GM ever spec'd.
I have never actually seen one, but I'm pretty sure Rodney's switch is a Wells SW555 as the specs match. It's from a late '80s 3.8 turbo, either a GN or a Firebird turbo. It is AFAIK the coldest one-wire fan switch that GM ever spec'd.
If you have a look HERE, you'll see that Rodney also sells a 195° on and 185° off fan switch (to be used with a 180° thermostat).
I did not say cooler ones didn't exist, I said the SW555 is the coolest one GM specified. I think that 195 degree switch is for an optional cooling package on a late C4 Corvette. That package was available "for race only" and not on emissions controlled vehicles.
Edit: And, again, 15 degrees is not a big enough spread between thermostat and fan switch, ever. Running a street car at those temps is madness. That would set a check engine light on pretty much every OBDII car in existence.
[This message has been edited by thesameguy (edited 03-20-2015).]
That seems rather unlikely.
