Radiator Fan Speeds/Temps


Dan S.

Well-known member
Oct 7, 2020
49
Just curious,

After reading some old threads regarding water temp ranges, I was curious if anyone knew what temperatures trigger the low, medium and high speed settings on fans to kick on?

We live in a town with a seasonal population and with the warmer weather coming in and more frequent bumper to bumper traffic, I'm seeing my temperatures increase in the 200 to 210 degree range. Turing on the a/c triggers the high speed fan and the temp comes down a bit... getting clean air in front of me brings it back down to around 180.

From my reading, these temps seem to be well within the normal range, but when I put the car away the other day, the tamp reading was 210 and the fans were not running which seems odd.

Getting ready to change the coolant (Snap On vacuum tool should be here by the weekend) which I'm sure will help - I believe I'm still on the original 2005 radiator fill.

Thanks,
Dan
 
Last edited:

Art138

GT Owner
Mark II Lifetime
Jan 4, 2011
624
Weston,FL
Do you have a transmission cooler? Not related to your post but might consider one. I live in hot South Florida and fastparts adjusted mine with their tune. After driving never had them stay on. Mine stays below 210.
 

nota4re

GT Owner
Mark IV Lifetime
Le Mans 2010 Supporter
Feb 15, 2006
4,176
GT coolant temps were a trade-off between consistently lower temps and fan motor/wiring longevity. There was plenty of experimentation by Ford engineers to make the right balance. In higher ambient temperatures, it is common to see 210F on the gauge. This is not indicative of any kind of problem and should be considered normal. Yes, a (qualified, like fastparts) tuner can re-program the fan speeds to come on at lower temperature, but I really believe that there was no incentive (emissions, mpg, etc.) that motivated the Ford engineers to choose the speeds that they did. Here in SoCal, we see our fair share of higher ambient temps but I've never seen a reason to re-program the GT.

In these temperatures, the transaxle is also running very hot. This is evidenced by oily vapor that escapes from the transaxle breather (top passenger side of the transaxle) and then collects on the outside and eventually the bottom of the transaxle. This is usually very visible from the top when you remove your air cleaner box and from the bottom when you have the rear pan off. Also, you will likely notice oil weeping from the hot transaxle vapors escaping through the bushings of the shifter rods where they enter the transaxle case. While a breather on the vent will address the symptom, a transaxle cooler will address the root problem and provide much cooler transaxle temps. This may have a small effect of engine temps but it will definitely prevent overheating of the clutch fluid and subsequent loss of the clutch pedal. More importantly, reduced transaxle temps is no doubt beneficial to the longevity of the transaxle.
 
  • Like
Reactions: Art138 and 2112

roketman

GT Owner
Mark IV Lifetime
Oct 24, 2005
7,994
ma.
I did one better and put in a racing radiator
The car rarely runs over 190
 

2112

Blue/white 06'
Mark II Lifetime
I did one better and put in a racing radiator
The car rarely runs over 190

Do you have pics of the installation?
.
 
In these temperatures, the transaxle is also running very hot. This is evidenced by oily vapor that escapes from the transaxle breather (top passenger side of the transaxle) and then collects on the outside and eventually the bottom of the transaxle. This is usually very visible from the top when you remove your air cleaner box and from the bottom when you have the rear pan off. Also, you will likely notice oil weeping from the hot transaxle vapors escaping through the bushings of the shifter rods where they enter the transaxle case. While a breather on the vent will address the symptom, a transaxle cooler will address the root problem and provide much cooler transaxle temps. This may have a small effect of engine temps but it will definitely prevent overheating of the clutch fluid and subsequent loss of the clutch pedal. More importantly, reduced transaxle temps is no doubt beneficial to the longevity of the transaxle.
I have a transaxle cooler and it works well during the summer when it's hot here in western Oregon. However, I have found that in the winter (when no cooler is needed) it takes noticeably longer to warm up the transaxle and therefore I block most of the cool air scoop on the right side of the car.
 

nota4re

GT Owner
Mark IV Lifetime
Le Mans 2010 Supporter
Feb 15, 2006
4,176
The cooling system of any modern car is, in reality, a system of systems. It would be really difficult to imagine that upgrading any single component would have a measurable improvement of capacity across the system. In the case of the GT, my opinion is that the OEM radiator is plenty large enough and is not the weakest link in the system. There is a lot of evidence that would suggest that airflow is the biggest factor in the GT's ability to shed BTUs. By elimination of the front protective grate (2005 cars), the rear grate (2005-2006), or the AC condensor (God forbid), the cooling capacity would be improved. A larger radiator with no more accessible airflow would seem to provide very modest if any returns.

That said, as I understand the OEM radiator has been discontinued (someone correct me if I am wrong) and so keeping an eye toward alternative radiators may, in fact, be a wise move!
 
  • Like
Reactions: PeteK and 2112

Dan S.

Well-known member
Oct 7, 2020
49
Thanks to everyone who replied - again I'm not concerned about the temps; what I'm seeing seems to be very typical.

My interest was that I was curious if anyone knew what temps triggered the slow, medium and high speeds for the fans.

Just ordered the the transaxle cooler - looks like a good project for a rainy day!

Dan
 
  • Like
Reactions: roketman

roketman

GT Owner
Mark IV Lifetime
Oct 24, 2005
7,994
ma.
Do you have pics of the installation?
.
I don’t
But Rich also sealed all around the rad pack so no air can blow by it
 

nota4re

GT Owner
Mark IV Lifetime
Le Mans 2010 Supporter
Feb 15, 2006
4,176
The OEM radiator is also painstakingly filled so that ALL available air is directed through the heat exchangers.
 

roketman

GT Owner
Mark IV Lifetime
Oct 24, 2005
7,994
ma.
No its not,or not as much as mine is now. I’m not saying it’s bad stock. It’s just improved now
 

nota4re

GT Owner
Mark IV Lifetime
Le Mans 2010 Supporter
Feb 15, 2006
4,176
No its not
I know you often put a lot of weight on things people tell you, but there's no substitute for experience.
 

roketman

GT Owner
Mark IV Lifetime
Oct 24, 2005
7,994
ma.
I think I can safely say that Rich Brooks has a a bit of experience
 

Art138

GT Owner
Mark II Lifetime
Jan 4, 2011
624
Weston,FL
Thanks to everyone who replied - again I'm not concerned about the temps; what I'm seeing seems to be very typical.

My interest was that I was curious if anyone knew what temps triggered the slow, medium and high speeds for the fans.

Just ordered the the transaxle cooler - looks like a good project for a rainy day!

Dan
I have the coolteck transcooler and installed myself. Very happy with it.
 

nota4re

GT Owner
Mark IV Lifetime
Le Mans 2010 Supporter
Feb 15, 2006
4,176
I think I can safely say that Rich Brooks has a a bit of experience
Indeed. And Rich has not said a single misleading thing on this thread. But you have. But it now appears that you really have no direct experience but rather you are *trying* to repeat what you thought you *heard*. Perhaps that's not so bad - but you are trying to correct ME on a topic where the best you have is hearsay.

So, let me try to enlighten you and provide more details on why I said that Ford did a GOOD job sealing up the airflow - to which you want to claim that I am wrong, or in any case, yours is better. Really? Let's see how the OEM GT airflow is very carefully managed... and then maybe you can illuminate us as to why yours is so much better.

Below is a pic of a GT that we recently repaired. (You can see the oopsie evidence with the bent front bumper beam.) But, this is a good picture to show how Ford has managed airflow through the heat exchangers. You can see the side skirts which prohibit any airflow around the sides of the stacked heat exchangers. On the bottom (and not shown) is a foam strip that runs across the bottom of the heat exchangers and it forms a seal between the heat exchanges and the large bottom splitter. You can clearly see the foam between each heat exchanger that prevent any air from escaping out the sides from in between. Finally, at the top of the radiators (and rolled toward the back in this pic) is a large rubber sheet. This prevents any air to escape from above the heat exchangers. This rubber piece is further held in place by the nose skin.

SealedGTNose.JPG

Please tell us again that my statement that the GT was "painstakingly sealed" is inaccurate. Your claim is that it is not... or at a minimum, your car is much better. Please enlighten us.
 

roketman

GT Owner
Mark IV Lifetime
Oct 24, 2005
7,994
ma.
Ok what ever you say!I’m not getting into a pissing contest with you. And am not going to waste my time.I am only relating my experience with what I have.As you are clearly an expert on everything.
But you do make great hood and clam shell struts!
As far as I’m concerned this thread is closed.
You can go argue or debate with sone else!
As It seems to please you. Have a nice day.
 
Last edited: