Erratic Radiator Fan Speed

[Ornery]

I've got a service manual for this '06, 4.6L Eddie Bauer, but I'm hoping somebody else has been down this road before, and can save me some time.

Occasionally, the fan radiator fan runs full speed for no reason. The first time I noticed this was on a cold start in the middle of winter. Fan would wind up to full speed right at start up, then wind down within 30 seconds. 30 seconds later it would speed up, and slow down shortly after. Not sure, but I think it eventually settled down as it warmed up.

The other day when it was rather hot, it went to full speed as I accelerated, then slowed down as the RPMs went down and the truck was cruising. Did it over and over every time I pulled away from a stop. After turning it off for about fifteen minutes, it didn't do it again after restarting and taking off again. Next day, it started doing the same thing all over.

Coolant level is topped off, and hasn't been low. I'm about ready to start throwing parts at it, but the only one I can think of is the coolant temperature sensor. Any others? Any tests to run? I'll check for codes, but there is no light on the dash, and hasn't been one for years.

TIA, John

 

[gdgiordano]

Mine does this too. I’ve never worried much about it. It is certainly worse when hot out.

 

[michael loibl]

Is the air conditioning or defroster on?

 

[gdgiordano]

Is the air conditioning or defroster on?

Mine does it regardless of what is on or off.

 

[Ornery]

Is the air conditioning or defroster on?

I leave EATC on automatic, with my side at 74° and my wife's side near 80°. It would sure surprise me if that had anything to do with the radiator fan. I've got a Motorcraft DY-1144 Engine Coolant Temperature Sensor and Motorcraft MOTRT1234 Thermostat arriving Sunday thanks to Amazon Prime. I hardly consider that a waste of money even if it doesn't change anything. And, if it doesn't, I can eliminate them as suspects.

 

[michael loibl]

If the system calls for the air conditioning compressor clutch to engage, it will most likely also call for increased radiatior fan speed. Try running truck a few minutes with auto climate OFF

 

[Ornery]

Well now, that makes sense. So, you would consider that behavior to be normal?

Won't have my hands on it again to late this evening. Just finished installing a blend door actuator in our '04 G. Marquis. If you thank that's a pain in a 4th Gen. Explorer, it's a piece of cake compared to the Panther!

I'll have my hands on the truck in the morning, when I'll put it through some tests before installing the sensor and thermostat. I'll post the results ASAP.

Thanks, John

 

[MotorCityFats13]

mine will rush on startup and settle and even with the A/C my scanner says it stays around 600rpm

 

[PotatoExplorer]

Mine does this almost every morning and settles down after a few seconds. Last summer my fan kept engaging and never disengaged. After trying a whole bunch of things and getting ready to replace the fan clutch, turned out to just be a simple thermostat.

 

[michael loibl]

Mine starts out engaged (loud) upon startup for about 10 seconds, then settles down until needed unless AC is on, then it stayed engaged

 

[Ornery]

Mid June in Northeast Ohio. Ambient temperature 64°... Sheesh. Anyway, that may be moot. On a cold start, the fan cycles on and "off" every 30 seconds perpetually, no matter if the EATC was on or off. After it was warmed up I didn't notice the fan running. But, on the next warm startup it revved up along with engine RPM. Seems to me the clutch was staying engaged, EATC on or off.

I get the impression, the fan clutch is either full engaged or not. I disconnected the clutch and the fan still spins, though not as fast.

Started getting cold feet about changing the thermostat. I'm surprised how buried it is in there, and I honestly don't even see the sending unit location. I assumed it was behind the thermostat housing. I'll change them anyway, but I'm doubting it will effect anything. Sure hope it's not the fan clutch itself. That's an expensive part, and probably corroded in place!

 

[Ornery]

Damn, I think I just wasted 90 minutes and $8.85 for a thermostat. I could find no Coolant Temperature Sensor in there. If anybody can point me to its location, I'd be very much obliged. I dug into the Service Manual and found this regarding the Temperature Warning Indicator:

Normal Operation

The powertrain control module (PCM) receives the
engine coolant temperature status through hardwired
circuitry to the engine coolant temperature (ECT)
sensor (4.0L engine), and from the cylinder head
temperature (CHT) sensor (4.6L engine). The
instrument cluster receives the engine coolant
temperature data from the PCM over the high speed
controller area network (CAN). The instrument
cluster monitors the engine coolant temperature data
received from the PCM and when the engine
coolant temperature is high, the engine over
temperature warning indicator illuminates.
​

As I mentioned, I've got the 4.6L engine. Just for the heck of it, I called Advance Auto Parts and asked if they had the Coolant Temperature Sensor for this truck, which he did for an off brand, double what I paid at Amazon for this Motorcraft unit. Amazon says it should fit my vehicle, but I'll have to return it if I can't figure out where it goes...

Edit:

Just found procedure for replacing the Cylinder Head Temperature Sensor

REMOVAL AND INSTALLATION
Cylinder Head Temperature (CHT)
Sensor — 4.6L (3V)

1. Disconnect the battery ground cable. For
additional information, refer to Section 414-01.
2. Remove the intake manifold. For additional
information, refer to Section 303-01B.
3. Disconnect the cylinder head temperature
(CHT) sensor electrical connector.
4. Remove and discard the CHT sensor.
5. To install, reverse the removal procedure.
​

That's going to require a little more ambition than I currently have!


Edit II:

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[MNgopher]

I was curious how this was going to work out - last check was there is no coolant temp sensor on the 4.6 V8 - only the Cylinder Head Temp Sensor. The Explorer V8 and Mustang V8 of the same timeframe both used this design. And yes- its buried under the intake manifold.

I'm wondering if the sensor listed is actually the Cylinder Head Temp Sensor - and that is what you've gotten. I can't find a different part number anywhere...

 

[Ornery]

Based on images I've seen of both parts, I do have the coolant temp sensor, which is heading back to Amazon. My only question now is, do I replace the clutch? It's interesting that its fluid has to warm up to function properly. Since mine is still original, it's not hard to believe this fluid may have changed properties over time and many cycles.

 

[Beachcomber86]

Before you replace the fan clutch, have you checked the wiring to the fan clutch. I'd wager a beverage that you have wiring harness issues. Fix that before you start replacing parts!

Found my ghosts in the machine

 

[Butch-Explorer]

My 06 4.6 use to do that before I bleed the air out of my radiator. Gas mileage was terrible also. Now its been running pretty good with temperature @ 192 - 197 degrees.

 

[Ornery]

Yikes, troubleshooting the electrical sounds daunting. There a several terminals in the connector. I've disconnected it, while running, and the fan slowed a lot. There are no codes at the moment, and I didn't have to erase any. There's no way I'm buying a $100 part, and going through the trouble to install it, without being reasonably sure it would fix it.

The Pinpoint Test E2 above, says to turn the key off, and see if it still "moans". How the hell could it still make any noise with the engine off? Anyway, I'll scour the manual for more clues.

Thanks for the help. I'll take all I can get!

 

[Beachcomber86]

Yikes, troubleshooting the electrical sounds daunting. There a several terminals in the connector. I've disconnected it, while running, and the fan slowed a lot. There are no codes at the moment, and I didn't have to erase any. There's no way I'm buying a $100 part, and going through the trouble to install it, without being reasonably sure it would fix it.

The Pinpoint Test E2 above, says to turn the key off, and see if it still "moans". How the hell could it still make any noise with the engine off? Anyway, I'll scour the manual for more clues.

Thanks for the help. I'll take all I can get!

It's not much electrical troubleshooting on the wiring. You'll see by inspection if you have a problem.

 

[BootyDo]

I wish I could help, but just to add my experience, mine did that when the AC was on, the car was running at full temp for maybe 15 minutes, and I came to a stop light. When the light turned green, sounded like a jet engine. I replaced the [leaking] radiator, fan clutch, radiator hoses, and thermostat. In warmer temps with no accessories, it now sounds like that for the first 5 seconds of startup and then stops. To be fair, I'm not very demanding of my AC and when the symptoms were bad, (and predictable), I noticed it lessened the number of times it would happen if I had the AC at a higher temp, (say 73ish).

One other symptom: when this would happen, if I turned my car off and right back on with no accessories, the fan would still run full throttle until I hit maybe 2nd or 3rd gear. Then it'd go away again.

Fan clutch was likely a waste of money. Hopefully yours is something easier!