Explorer Sucking in a lot of Air??

[PotatoExplorer]

Hmm, I think I figured it out!! The wife tried to drive it today with little success. Thankfully no damage (yet) since she pulled over several times to let it cool down before it got up into the red. Anyways, I went out and bought a new thermostat from Autozone and attempted to replace it.

Pretty easy job - took off the air intake duct, throttle body, drained radiator, pulled upper radiator hose and clamp from the upper thermostat housing, removed upper thermostat housing, pulled out the old gasket and thermostat, cleaned upper and lower thermostat housings, installed new thermostat, oiled up and installed new gasket, and then put back everything. I then ran over to Walmart to get several gallons of Prestone 50/50 ready mix. Not sure if this is recommended, but... whatever. Used the funnel again to fill up the radiator. Filled it up just so a little coolant was up into the bottom of the funnel. Filled overflow to the cold fill mark. Started it up and purged the system for about 30 minutes. Revved it up to 3k for a minute or two several times. Did several cycles of heat/ac and several massages of the upper/lower radiator hoses. Lots and lots of bubbles worked their way out of the system.

The fan never kicked onto crazy high speed. Temp gauge never spiked. The bottom radiator hose got warm once the vehicle got up to normal operating temperature. Took it on a 15 minute test drive and drove it aggressively to get the fan to kick on since it's like 20 degrees cooler today (and raining). Fan never kicked on to a point where it sounded like I was flying a jet plane. The loud rush of air is gone!

Something was definitely messed up with the thermostat. I was having a good bit of difficulty removing the upper thermostat housing since the thermostat was sticking up (from what I looked up, this would mean the thermostat was closed). I had to jiggle the housing around until the thermostat snapped back down to the open position. I think I'll try to purge the system one more time and do another test drive when it's really hot again... now back to my RPM surging issue.

So the culprit was a thermostat stuck in the closed position.

 

[Mart1n]

Hmm, I think I figured it out!! The wife tried to drive it today with little success. Thankfully no damage (yet) since she pulled over several times to let it cool down before it got up into the red. Anyways, I went out and bought a new thermostat from Autozone and attempted to replace it.

Pretty easy job - took off the air intake duct, throttle body, drained radiator, pulled upper radiator hose and clamp from the upper thermostat housing, removed upper thermostat housing, pulled out the old gasket and thermostat, cleaned upper and lower thermostat housings, installed new thermostat, oiled up and installed new gasket, and then put back everything. I then ran over to Walmart to get several gallons of Prestone 50/50 ready mix. Not sure if this is recommended, but... whatever. Used the funnel again to fill up the radiator. Filled it up just so a little coolant was up into the bottom of the funnel. Filled overflow to the cold fill mark. Started it up and purged the system for about 30 minutes. Revved it up to 3k for a minute or two several times. Did several cycles of heat/ac and several massages of the upper/lower radiator hoses. Lots and lots of bubbles worked their way out of the system.

The fan never kicked onto crazy high speed. Temp gauge never spiked. The bottom radiator hose got warm once the vehicle got up to normal operating temperature. Took it on a 15 minute test drive and drove it aggressively to get the fan to kick on since it's like 20 degrees cooler today (and raining). Fan never kicked on to a point where it sounded like I was flying a jet plane. The loud rush of air is gone!

Something was definitely messed up with the thermostat. I was having a good bit of difficulty removing the upper thermostat housing since the thermostat was sticking up (from what I looked up, this would mean the thermostat was closed). I had to jiggle the housing around until the thermostat snapped back down to the open position. I think I'll try to purge the system one more time and do another test drive when it's really hot again... now back to my RPM surging issue.

So the culprit was a thermostat stuck in the closed position.

Hi, I have a similar issue. You're fan never came back on (meaning excessively) since you changed the thermostat? Because if your thermostat was closed the truck would have overheated. I don't have any overheating issue, just the fan working too much (not constantly). Trying to figure this out for a while now. Thanks

 

[PotatoExplorer]

Nope, still hasn't kicked on like it did since I replaced it. I don't believe the thermostat was closed completely but was closed enough to make it almost overheat if I drove it long enough. Yours could also be air trapped in the lines. Try working out any air bubbles first. If not that then could also be just your fan clutch going out.

 

[Mart1n]

My temp reading is steady in the middle of the dashboard gauge (no spikes either). If I unplug the fanclutch it stops, so it is not seized. So I'm looking towards temperature sensor malfunction or maybe a faulty PCM / TCM signal.

Do you think I'm missing something?