2014 3.6 V6 Radiator fan only runs on low

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SJGUSMC21

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GM. Last summer/fall (the difference is overnight here in San Antonio) I was driving home in traffic and my truck overheated. I pulled off and let it cool off. Finally was able to get home. I swapped out the thermostat (98K miles), flushed and replaced the coolant. Seemed to run just fine, but the weather did cool off.

Fast forward to present. Was driving home (temp was around 70) and my temp gauge shot up to 241. I also noticed I didn't have any hot air from the heater. I pulled over and let it cool off, and then drove home (very short drive). Truck now has 104K on it. When I checked the coolant, it was almost a gallon low! No puddles, nothing. My engine also has no oil leaks, runs great. Filled it back up and decided to go ahead and swap out the water pump, upper and lower radiator hose and top off the coolant. Took it for a drive, seemed fine...was staying at around 190 then it started climbing...got up to 225. When I arrived home, I discovered a small leak coming from the upper radiator inlet hose. Sure enough, there is a minute crack in the neck. Ordered a radiator, got it replaced, and no more leaking. However the temps seem the same, then starts climbing back up. I have noticed that my fan only stays in low speed, and never goes to high speed, as it used to do. Could this indicate that the fan motor/electronics in it are going bad? It is a electronic PWM fan.

Any help would be greatly appreciated. I am not a mechanic, but I try.

Semper Fi!
 
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SJGUSMC21

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Anyone? Well, I went ahead and ordered a fan. This one only rocks a bit, then spins but only a low speed.
 
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jws123

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Make sure you burped all of the air out of the system also have you scanned it for codes normally when fan fails it will throw a code.
 
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SJGUSMC21

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I have burped it from the thermostat nipple. There have been no codes, no CEL's, I would have seen that. The fan hasn't 'failed' as it still turns....just at low speed. I watched it again today, and it will move a bit left and right, then slowly spin up to low speed, for a very short time, then stop, rinse and repeat. In the fuse box, I do not have the left and right relays, nor the 60 amp lo/hi fuse, just the 80 amp PWM fuse.

Thanks for the info.
 

csuder99

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IIRC the fan has three connections, power, ground and the PWM control signal. I'd start checking that power and ground are good, a high resistance ground will cause all sorts of weird issues. If you have AlfaOBD you can control the PWM pulse width and monitor with a low amp test light.
 

pacofortacos

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Most 3.6 engine will have a failed head gasket at this point - which is what I am guessing is happening to you now.
Been there done that.

I would get it checked before you do permanent damage to the engine.
 
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SJGUSMC21

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Thank you for your help. Once i get the fan installed, if this doesn't solve my issue, then I will certainly get it checked out, as this is my last option. As for a failed head gasket, these are the symptoms I found that should indicate that you have a blown head gasket. Of them, only the engine overheating or running hot applies to me. I had a blown head gasket in an Ford ****** (don't know why it blanks out the name) station wagon, a long time ago, and these symptoms were present. And even if it is my head gasket, still doesn't explain why fan is running on low only.

Bad head gasket symptoms
  • White smoke coming from the tailpipe. (zero smoke and runs smoothly, no rough idle, nothing)
  • BUBBLING IN THE RADIATOR AND COOLANT RESERVOIR. (no bubbling at all)
  • unexplained coolant loss with no leaks. (leak was at the upper intake nozzle of radiator, observed, and replaced)
  • Milky white coloration in the oil. (I change the oil myself, oil was fine)
  • Engine overheating.
I do not have a AlfaOBD. Again, if the new fan doesn't solve my issue, then I will have my truck serviced.
 
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pacofortacos

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I had my 3.6 in my Pacifica fail and the only symptom was no heat and high temp - due to coolant loss.

Is you temp rising while moving at higher speeds or just at idle?
 

jws123

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I would also double check the tstat have had brand new ones be bad more common then it should be.
 
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SJGUSMC21

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My heater pours out the hot air, which is a good thing. I drove into work today and it did reach 221 after I got to work (after I parked, fan did not come on). During the drive here, it stayed pretty much at 204 (between 198 and 206), but when I hit heavy traffic (almost to work) it started heating up and when I turned the engine off it was at 221.
 
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SJGUSMC21

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I would also double check the tstat have had brand new ones be bad more common then it should be.

Yeah, when this all started, my upper radiator hoses had little pressure. Now, I have lots of pressure in them and I can see (I believe) when the thermostat opens....it will go from 205ish down to 196 or less kind of quickly. From what I have read, both of these actions indicate that the T stat is working. I could be wrong though.
 
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SJGUSMC21

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Got the new radiator fan in today, took about 15 minutes to install and it was most certainly my fan. Woohooo. Got it in and tested it...works like a champ and it is SO GOOD to hear the fan at hi speed once again. Opened her up on the intersate with AC on and off, never got above 212, was mostly around 205. Sitting at a light, I could hear the fan running at high setting. Thank you all for your help and input. Hope this helps some one.
 
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