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Discussion Starter · #1 ·
I have a 2003 Honda Pilot that overheats after about 20 mins of idle, neither of the fans activate by themselves. I have tested both of the fans and relays separately with the battery. I've opened up the relays while connected and activated them manually and fans activate only that way. I have tested and replaced the temperature sensor connected to the radiator as well with replace the radiator. I have also tested the sensor on the thermostat body and the thermostat is new. I have no other ideas of what it may be so I'm asking for your help. Thank you.
 

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I have a 2003 Honda Pilot that overheats after about 20 mins of idle, neither of the fans activate by themselves. I have tested both of the fans and relays separately with the battery. I've opened up the relays while connected and activated them manually and fans activate only that way. I have tested and replaced the temperature sensor connected to the radiator as well with replace the radiator. I have also tested the sensor on the thermostat body and the thermostat is new. I have no other ideas of what it may be so I'm asking for your help. Thank you.
20 minutes worth of idling doesn't necessarily = hot enough to activate fans.
Do the fans come on with the AC compressor coming on?
Do you have a OBD II scanner to get live data?
Fan should kick on at 205°F and off at 190°.
 

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Nobili spiritus embiggens pequeño sparus tyre.
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How's the heat in the cabin?

You say the thermostat is new. Did these symptoms start appearing after it was replaced? If so, what brand thermostat, where did you get it, and who installed it?

Also, what made you decide to replace it?
 

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Discussion Starter · #5 ·
20 minutes worth of idling doesn't necessarily = hot enough to activate fans.
Do the fans come on with the AC compressor coming on?
Do you have a OBD II scanner to get live data?
Fan should kick on at 205°F and off at 190°.
Will confirm that tomorrow have to recheck
 

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Discussion Starter · #6 ·
How's the heat in the cabin?

You say the thermostat is new. Did these symptoms start appearing after it was replaced? If so, what brand thermostat, where did you get it, and who installed it?

Also, what made you decide to replace it?
The heat is instant, I was told by previous owner that he replaced it because of the issue and it looks brand new, is there a specific brand that is preferable for my vehicle?
 

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How's the heat in the cabin?

You say the thermostat is new. Did these symptoms start appearing after it was replaced? If so, what brand thermostat, where did you get it, and who installed it?

Also, what made you decide to replace it?
Incorrect thermostat installation can create problems. OP checked the radiator cap?
 

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Nobili spiritus embiggens pequeño sparus tyre.
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Incorrect thermostat installation can create problems. OP checked the radiator cap?
Exactly, that's one of the things I was getting at. Worth looking into it, since it's a relatively recent variable.
 

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The heat is instant, I was told by previous owner that he replaced it because of the issue and it looks brand new, is there a specific brand that is preferable for my vehicle?
It just seems crazy that any thermostat won't work. It's not the first time that I have heard this. This is supposed OE Temp fail safe. Seems to be popular on RA.
147378
 
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Discussion Starter · #10 ·
Exactly, that's one of the things I was getting at. Worth looking into it, since it's a relatively recent variable.
When the temperature reached 205 and up none of the fans activated, made sure the coolant was at correct level, is there a video with correct thermostat installation, I will be checking that next.
 

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Discussion Starter · #12 ·
I have also noticed that the wiring harness to the fans go into this hiding relay box could it also have something to do with it (edit) actually goes into main relay/fuse box but that connects to that little box
 

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I have also noticed that the wiring harness to the fans go into this hiding relay box could it also have something to do with it (edit) actually goes into main relay/fuse box but that connects to that little box
You have hot wired each fan separately to the battery?
 

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One of those point-n-shoot IR temp guns would be handy about now.

I’m puzzled about the “Fail Safe” t-stat. Most t-stats are wide open 15-20 degrees above open temp, so at 190F a 170F rated t-stat would/should be wide open. I’m wondering at what temp does it “fail safe” or lock open? Got to be north of 205F. The “fail safe” t-stats I’ve removed from overheated motors have always been “locked” open, can not close.🤷‍♂️
 

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Yes I have separately and they both work
Either the AC will cause the fans to turn on or the temperature sensor. Check fuse, relay, conections (bent prong) continuity though wiring. At that point if all good, I'm replacing the temperature sensor at the bottom of my radiator.
 

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While it should never overheat, why may I ask do you need to idle 20mins? Waiting and using the heat or cooling?
 

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Discussion Starter · #18 ·
Either the AC will cause the fans to turn on or the temperature sensor. Check fuse, relay, conections (bent prong) continuity though wiring. At that point if all good, I'm replacing the temperature sensor at the bottom of my radiator.
I have tested those connections as well and they seem to work
 

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Discussion Starter · #19 ·
While it should never overheat, why may I ask do you need to idle 20mins? Waiting and using the heat or cooling?
It starts to warm up around 20 or more minutes and I can drive it perfectly fine but just don't want radiator to blow
 

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When the temperature reached 205 and up none of the fans activated, made sure the coolant was at correct level, is there a video with correct thermostat installation, I will be checking that next.
May I ask what was used to determine temp reached 205 and up?
 
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