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Old 09-01-2007, 09:40 PM   #1
wolfman04
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Default At what temperature does radiator fan come on?

Have stock thermostat in my 04 at what temperature should the radiator fan come on?
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Old 09-01-2007, 11:10 PM   #2
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From the Service Manual .....

The low speed cooling fan is commanded on when the coolant temperature reaches 108C (226F). It is turned off if the coolant temperature lowers to 104C (219F). The high speed cooling fan is commanded on when the coolant temperature reaches 113C (235F). It is turned off if the coolant temperature lowers to 108C (226F). When the A/C is on and the coolant temperature reaches 85C (185F), the low speed cooling fan will be turned on at vehicle speeds less than 56 kPh (35 mph).

While the manual refers to a "fan", there are two fans behind the radiator .... they run together in either LOW or HIGH speed mode.
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Old 09-02-2007, 09:30 AM   #3
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Quote:
Originally Posted by BlackZ06 View Post
From the Service Manual .....

The low speed cooling fan is commanded on when the coolant temperature reaches 108C (226F). It is turned off if the coolant temperature lowers to 104C (219F). The high speed cooling fan is commanded on when the coolant temperature reaches 113C (235F). It is turned off if the coolant temperature lowers to 108C (226F). When the A/C is on and the coolant temperature reaches 85C (185F), the low speed cooling fan will be turned on at vehicle speeds less than 56 kPh (35 mph).

While the manual refers to a "fan", there are two fans behind the radiator .... they run together in either LOW or HIGH speed mode.
Thanks
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Old 09-02-2007, 10:30 AM   #4
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fyi, the thermostat does not control the fans, the PCM does.
When the thermostat opens water instead of recirculating through the block is routed through the radiator.
If you want your fans turned on at a lower temperature you need a programmer. Like Tech II, HP tuners etc....
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Old 09-02-2007, 08:19 PM   #5
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Quote:
Originally Posted by rws.1 View Post
fyi, the thermostat does not control the fans, the PCM does.
When the thermostat opens water instead of recirculating through the block is routed through the radiator.
If you want your fans turned on at a lower temperature you need a programmer. Like Tech II, HP tuners etc....

I wanted my fans to turn on at a lower temp... what temperature should i set them at to turn on... Is it bad if i set them to turn on to low? thanks
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Old 09-03-2007, 10:01 AM   #6
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Quote:
Originally Posted by 01 stock c5 View Post
I wanted my fans to turn on at a lower temp... what temperature should i set them at to turn on... Is it bad if i set them to turn on to low? thanks
This subject has been beat to death on these forums .... to summarize ....

One position .... GM Powertrain Division spent a lot of engineering time, and money, developing the cooling system for your engine. They chose the fan speeds, on/off temperatures, coolant flow rate, radiator size, etc. based on science and engineering

Other position ... GM Powertrain was wrong, and some people know better than the engineers what temperature the engine should run at.

If you buy the first arguement, LEAVE THE SYSTEM ALONE.

If you buy the second arguement, then install a 160 degree or 180 degree thermostat, and use a Ouija board to figure out the on/off temps for the fans ... or just put temps on a dart board and select them that way.

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Old 09-03-2007, 10:27 AM   #7
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Quote:
Originally Posted by BlackZ06 View Post
If you buy the second arguement, then install a 160 degree or 180 degree thermostat, and use a Ouija board to figure out the on/off temps for the fans ... or just put temps on a dart board and select them that way.

Jim at SWTuning in OKC, who I never have heard a negative post about or comment about, told me to install a 160 stat before the dyno tune - guess he uses a Ouija board or the dart method.

Last edited by Bullet; 09-03-2007 at 10:28 AM. Reason: too wordy
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Old 09-03-2007, 10:32 AM   #8
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Quote:
Originally Posted by BlackZ06 View Post
One position .... GM Powertrain Division spent a lot of engineering time, and money, developing the cooling system for your engine. They chose the fan speeds, on/off temperatures, coolant flow rate, radiator size, etc. based on science and engineering
You forgot to add the EPA or Federal emission people.
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Old 09-03-2007, 09:29 PM   #9
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You're better off using a PCM tuner like a Diablo to set the fan parameters. All the 160 is going to so is open at 160...not make the engine run at 160.

Using the Diablo...my car never goes over 192...before I saw 230 at times stuck in traffic on a hot day!


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Old 09-04-2007, 07:51 PM   #10
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Jim at SWTuning in OKC, who I never have heard a negative post about or comment about, told me to install a 160 stat before the dyno tune - guess he uses a Ouija board or the dart method.
The 160* thermo starts opening at 160, and is not fully open until 178-180. Fan turn on and off (this is known as the hysteresis-the difference between on and off points) is set up to keep the motor between 182 and 195 degrees.

The 160* thermo naming is goofy and somewhat incorrect, from what we are used to, but that's the way it is.

The colder operating temps allow slightly more power and safety margin for detonation to be had.

It is important to note that coolant temperature does not make power, but rather colder air does. That said, the colder thermo allows slightly colder cylinder head metal temps, and in effect, slightly colder air in the chamber itself.

A couple of eons ago, I tested the whole coolant temp thing, and found, at the time, on several different engine configs(GM and Ford), that each 5-7 degrees coolant temp drop allowed me to run 1 extra timing degree. in the 3D timing tables, pretty much globally.

Why did oem run them so hot? Emissions and fuel efficiency. Thinner oil and well expanded cylinder bores.

Nutshell is that 180-200 is a good range of performance engine temps, and even at that range of temps, I still can pass emissions testing quite well.

Never messed with a OUIJA board.
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Old 09-05-2007, 03:13 AM   #11
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Quote:
Originally Posted by hex View Post
The 160* thermo starts opening at 160, and is not fully open until 178-180. Fan turn on and off (this is known as the hysteresis-the difference between on and off points) is set up to keep the motor between 182 and 195 degrees.

The 160* thermo naming is goofy and somewhat incorrect, from what we are used to, but that's the way it is.

The colder operating temps allow slightly more power and safety margin for detonation to be had.

It is important to note that coolant temperature does not make power. , but rather colder air does. That said, the colder thermo allows slightly colder cylinder head metal temps, and in effect, slightly colder air in the chamber itself.

A couple of eons ago, I tested the whole coolant temp thing, and found, at the time, on several different engine configs(GM and Ford), that each 5-7 degrees coolant temp drop allowed me to run 1 extra timing degree. in the 3D timing tables, pretty much globally.

Why did oem run them so hot? Emissions and fuel efficiency. Thinner oil and well expanded cylinder bores.

Nutshell is that 180-200 is a good range of performance engine temps, and even at that range of temps, I still can pass emissions testing quite well.

Never messed with a OUIJA board.
Fuel efficiency = POWER ..... if you're burning ALL the fuel ... you're getting MAXIMUM power .... unburned fuel is LOST POWER ..... You want MAXIMUM FUEL EFFICIENCY in ANY engine ...

Cooler intake air is denser ... allowing you to put more fuel into the charge ... that's where POWER comes from .... not a cooler engine ....

If a cooler engine is more powerful ... then answer this ... why do NASCAR engines run in the neighboorhood of 220-230 degrees ... why do Champ Car engines run in the neighborhood of 215 degrees (they burn methanol) and why do Formula1 engines run in the neighborhood of 230 degrees ... think those guys want POWER ???????
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Old 09-05-2007, 10:04 AM   #12
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Yes, there is always someone who knows more.

Alcohol, be it, methanol, or ethanol, run very cool temps, and I always run them at 220-235* F, in addition to a 22* radiator cap. Those motors need heat and compression to be efficient, and comparing an alcohol burning motor to a gasoline user is exactly comparing apples to oranges. E85 is pretty close to the same to 100% alky, as far as thermal efficiency and tuning goes, with the exception of the lower BSFC rate.

My apologies to the gentleman whom owns this thread and posed the original question. Here is the answer:

oem fan temps on an auto 04 car:

fan1 on at 226, off at 219

fan2 on at 235, off at 227

if you want to turn the fans on sooner with your stock thermo, keep the fan1 turn off point at 200 or above.

For example:

fan1 on at 206, off at 200
fan2 on at 212, off at 206.

Hope this helps.
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Old 09-05-2007, 10:04 AM
 
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