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Randomly coolant fans on high speed at idle

Tiny
1BIGEYE
  • MEMBER
  • 2011 FORD ESCAPE
  • 3.0L
  • V6
  • 4WD
  • AUTOMATIC
  • 200,000 MILES
Coolant fans are coming on (high speed) at idle (parked) and when you come to a stop while driving. They come on randomly at high speed. When driving they will go off, only come on randomly when stopping or parked at idle.
I looked at the high pressure A/C switch thinking it might be opening (NC open on high pressure) randomly when fan came on at idle. Disconnected switch when fans came on at Idle and fans remained on at high speed. Then they would turn off after a few minutes at idle. Could the ECT be randomly failing sending a signal to the ECM to turn fans on? The fans run normal while driving and there is no heating or cooling problem. I thought if I was getting poor heat transfer through cooler the fans would stay on all the time, not randomly coming on and off at high speed?
I am still troubleshooting, next I am going to take temperature readings when the fans come on at idle.
I have never seen where fans come on at high speed randomly at engine idle. ECT is the only other player in this picture unless I am missing something?
Any help or guidance would greatly be appreciated.
Thanks,
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Friday, September 4th, 2020 AT 9:49 AM

7 Replies

Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Good afternoon,

This sounds normal. Depending on outside temperature, the fans should and will come on to cool down the engine.

https://www.2carpros.com/articles/how-an-electric-cooling-fan-works

What makes you think it is the issue? Do you have any concerns?

The fans should come on at 208 degrees and turn off at 187 degrees.

The fan could be on low or high depending on the outside temperature.

Roy
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Friday, September 4th, 2020 AT 10:46 AM
Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
Is there something else going on that would cause you to think this is an issue? This sounds like the fans are coming on to keep the temp where it should be.

Does the vehicle overheat or run poorly?

From the sound of it, this is not uncommon for the fans to come on high at idle and then shut off a short time later. Basically if the engine is not overheating then I would not worry about the fans coming on high and then off.

Let me know if I am missing something. Thanks
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Friday, September 4th, 2020 AT 10:52 AM
Tiny
1BIGEYE
  • MEMBER
  • 3 POSTS
Fans come on high speed and have never done this before ever. So it’s possible My cooler is degraded and needs flushing. I will take temp data while the fans are on, then flush coolant system and wash down and clean radiator of any debris and see if the Delta-T comes down. Does my coolant system require air bleeding? I have read that some ford engines create air pockets when refilling system. I don’t have a radiator cap on cooler it all goes through the reservoir. I will post the results after I do the flush. Thanks for your input. David
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Friday, September 4th, 2020 AT 4:25 PM
Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
I attached the entire cooling system process including the bleed procedure because you do have bleeder valves. Let us know how it turns out. Thanks
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Friday, September 4th, 2020 AT 8:28 PM
Tiny
1BIGEYE
  • MEMBER
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Thanks for the cooling data guidance. After flushing/bleeding system and cleaning coolers it didn’t make any noticeable difference. Actually the issue is getting worse. The fans go into high speed and extreme high vibration. The temperature is normal and no change in engine RPM's. The fans cycle on and off every 5 minutes. I am not sure what makes the fans go into this high speed and high vibration mode of operation. I checked the fan mounting brackets and based on how it’s designed, I didn’t see any bushing degradation that would contribute to the vibration that is happening when these fans go into this high speed mode of operation. Is there a fan speed controller integrated into this fan design? Next step looks like I need to replace the fan assembly. I have seen a couple videos on how this is done. Any additional guidance or input would be greatly appreciated. Thanks for your support. David
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Monday, September 14th, 2020 AT 6:16 PM
Tiny
4DRTOM
  • MECHANIC
  • 467 POSTS
Hello,

It sounds to me light you cooling fan relay is sticking. Below is the electrical diagram for that circuit and the fan relay location.
Let me know if this helps and if you need any other assistance.
Tom
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Monday, September 14th, 2020 AT 10:17 PM
Tiny
ASEMASTER6371
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Good morning again.

The vibration is not normal. That could be the motor itself causing this issue.

The high and low speeds are normal based on the temperature of the coolant . The signal for that comes from the coolant sensor and the ECM will command high or low based on that input.

A couple of suggestions.

1. Replace the thermostat. If it is opening a little later than it should, it could cause this type of operation even though it is not overheating.

https://www.2carpros.com/articles/how-an-engine-thermostat-works

https://www.2carpros.com/articles/replace-thermostat

2. The coolant sensor itself.

https://www.2carpros.com/articles/how-a-coolant-temperature-sensor-works

https://www.2carpros.com/articles/coolant-temperature-sensor-cts-replacement

3. The fan motor. That could be the reason for the vibration that bothers you.

https://www.2carpros.com/articles/replace-electric-fan-motor

Roy

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Tuesday, September 15th, 2020 AT 3:26 AM

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