Cooling Fan not going high speed when idling - truck starts to overheat

[mike199]

Hi, has anyone experienced the cooling fun only go high speed when under load? Mine recently stopped kicking in while idling so it starts overheating after 30min idle with ac on and 1h without ac (when it worked I was able to idle for hours(job requirements) with ac on and it was constantly kicking in on high). Thermostat and fun clutch was replaced, cooling system flashed 2 times. 3 shops couldn't find anything, any ideas would be greatly appreciated. Thanks!

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[airline tech]

Clogged Radiator (internally) or leaves and debris between the condenser and radiator blocking airflow are the first thoughts. Since you are idling when it overheats as when driving you are forcing airflow across the radiator - providing the additional cooling.
Another would be a bad Reservoir Cap or a leak in the system, not allowing it to pressurize properly and also allowing air to enter the system, thus creating air pockets.
With your issue only showing at idle, I suspect a blockage of airflow at the radiator.
Now for the Temp Sensor - Either CHT or ECT can be reading incorrectly.

 

[RangerBill]

Do you have any DTC codes?

 

[mike199]

Temp sensor was not replaced, only thermostat and fan clutch assembly. No leaks, and the dirt would not affect the cooling fan not ramping up without load would it? Because I I was idling and it was almost constantly high speed 1 day and next morning and never since it got on high speed. But if I idle and press gas pedal, it start going high speed and starts to cool itself. I am thinking about some kind of relay/ wiring? maybe look into the voltage of either fan or temp sensors?

 

[mike199]

Do you have any DTC codes?

there was one for a moment for the high coolant temp, but it went away when the truck cooled down

 

[RangerBill]

there was one for a moment for the high coolant temp, but it went away when the truck cooled down

What was the code?

 

[mike199]

What was the code?

good question, unfortunately it went away before I was able to take picture and it didn't stay in any logs

 

[RangerBill]

good question, unfortunately it went away before I was able to take picture and it didn't stay in any logs

Is the fan clutch wiring harness or connector damaged? Have you checked for a loose or poor connection at the fan clutch wiring connector?

 

[mike199]

Is the fan clutch wiring harness or connector damaged? Have you checked for a loose or poor connection at the fan clutch wiring connector?

fan clutch wiring harness or connector both look good, no damage

 

[mike199]

Do you have any DTC codes?

If I remember correctly it was P0217 for engine coolant overtemperature condition but I will to replicate this week to confirm

 

[cfhgarza]

Isnt it belt driven? So the engine rpm would determine the speed and the clutch just engages and disengages the fan?

 

[mike199]

I don't think so as it worked with low and high speed on idle for me for over 2 years and 150kkm, and one day just stopped doing that

 

[airline tech]

Yes it is belt driven , however electrically can be controlled to spin faster than engine RPM.
When you First start the truck when cold - does the fan sound louder for the first few minutes of engine running? And then back down?
There are various inputs for how the PCM controls the fan speed, the most important is the CHT - Cylinder Head Temp sensor, so that temp pickup is critical to coolant flow, with you stating that the issue is prevalent at idle , I suspect a low flow issue or a blockage of airflow across the radiator, address the reason for the fan needing to speed up in the first place, I idled my truck in the heat and have never heard the fan increase speed.
So step 1 - what is causing the low flow and then diagnose why when it reaches the (overheating) point and the PCM is programmed to speed up the fan - it’s not working, without a bi direction scan tool to command control the fan it’s a crap shoot.
A quick test of all temp sensors is to get live data PIDs of all temp sensors on a cold engine, they should all match within a few degrees of each other.
Ambient, CHT , ECT, IAT and IAT2, I have a hunch the CHT may be under reading as it is the primary temp sensor with the ECT being secondary.
Note: I did edit my post as my first read of it caught the T-Stat but in my head was thinking temp sensor and when I got to the post, I typed temp sensor.
Has fluid level been dropping ?
You may have an internal leak, more so the EGR Cooler or Head Gasket- Pressure Test will show good @ 21 PSI and also the Cap is another overlook part that can cause improper flow.
I think you have a combination of 2 issues. Improper pressure or flow at low idle and then a temp sensor issue.

 

[mike199]

Yes it is belt driven , however electrically can be controlled to spin faster than engine RPM.
When you First start the truck when cold - does the fan sound louder for the first few minutes of engine running? And then back down?
There are various inputs for how the PCM controls the fan speed, the most important is the CHT - Cylinder Head Temp sensor, so that temp pickup is critical to coolant flow, with you stating that the issue is prevalent at idle , I suspect a low flow issue or a blockage of airflow across the radiator, address the reason for the fan needing to speed up in the first place, I idled my truck in the heat and have never heard the fan increase speed.
So step 1 - what is causing the low flow and then diagnose why when it reaches the (overheating) point and the PCM is programmed to speed up the fan - it’s not working, without a bi direction scan tool to command control the fan it’s a crap shoot.
A quick test of all temp sensors is to get live data PIDs of all temp sensors on a cold engine, they should all match within a few degrees of each other.
Ambient, CHT , ECT, IAT and IAT2, I have a hunch the CHT may be under reading as it is the primary temp sensor with the ECT being secondary.
Note: I did edit my post as my first read of it caught the T-Stat but in my head was thinking temp sensor and when I got to the post, I typed temp sensor.
Has fluid level been dropping ?
You may have an internal leak, more so the EGR Cooler or Head Gasket- Pressure Test will show good @ 21 PSI and also the Cap is another overlook part that can cause improper flow.
I think you have a combination of 2 issues. Improper pressure or flow at low idle and then a temp sensor issue.

That's great info. Yeah the fan gets loud when I start driving when the engine is cold, settles down after a few hundred meters.
I am guessing good shop would have that kind of bi directional scan tool to test the fan?

''I idled my truck in the heat and have never heard the fan increase speed.''- I have access to 4 different cars at this moment and all of them are having the fans going high speed on and off constantly whenever the AC is on, with that being said, I should clarify that it happens in ranger with the ac on after around 30mins while idling, I get warm air from vents after 15-20mins, when I don't have ac on, it would take 1h.30-2h to see the temp raising on the gauge, I will need to idle tomorrow at work and I will check the values and codes in forscan and hp tuner.

No fluid leak or level changing, and with 2 flushes 1 by ford dealer and 1 by 3rd party shop didn't show any issues assuming there would be a problem with the internal flow through the radiator and the rest of the system when it's being flushed.

Also the ac was checked for leaks, there were none and the ac system was recharged recently.

 

[RangerBill]

Have you checked that the A/C condenser in front of the radiator is not clogged with dirt or debris and the radiator fins are clear of debris? How high is the temperature gauge reading? Have you tried removing the tune?

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