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Discussion Starter · #1 · (Edited)
I removed my VCM disabling device today and plugged my scan tool in to monitor the coolant temperature while I was driving today.

While idling after the engine was warmed up, the temp got up to 225. Is that normal? It hovered around 206-208 while driving. This was with no VCM disabling installed during this time.

The coolant level is good in the radiator and the overflow tank. I assume the only other thing it could be is a thermostat?
Any suggestions on how to further test this?

I should add, the fan does not come on when the temperature reaches 200+ which leads me to believe something may be wrong with the fan. Any ideas?

Thanks for you input.
 

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Nobili spiritus embiggens pequeño sparus tyre.
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If you're pretty sure it's a bad thermostat, just go ahead and replace it, since they're cheap enough. Less costly than a blown head gasket, anyway.

2006 HONDA PILOT 3.5L V6 Thermostat | RockAuto

Check, or actually just change your upper and lower hoses. I changed all that when I put in a new Denso radiator last year. I can't remember, have you ever changed your radiator?

Might also want to test your coolant strength. If you don't have a tester, they're also pretty inexpensive. I don't know why I keep forgetting to buy one whenever I'm at an auto parts place, but I should.
 

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Discussion Starter · #4 ·
So to add something exciting to the story, I was sitting in a drive thru this evening and the gauge went to almost 3/4 of the way. As soon as I drove away, the gauge went back down. The more I revved the engine, the lower the temp got. I also noticed the fan's weren't turning on.

I'm not really interested in throwing a bunch of parts at it and I don't really have time to do it myself so I want to have some general idea of what is wrong before I go to the shop

Based off of this, would it point to the fans being the issue?
No coolant loss, no white smoke, just changed the oil and everything was good. The thing that confuses me, is the temp goes back down to normal ~206 degrees when I'm revving the motor.

The coolant was completely changed May 2020 when the timing belt was changed. Radiator is original as are the hoses.
 

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Test your fans. Make sure they both come on.

The thing that confuses me, is the temp goes back down to normal ~206 degrees when I'm revving the motor.

Tensioner and/or water pump not doing their job? Assuming they were changed with the timing belt, who installed them and what brand were they? Not Gates, I hope.

 

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I believe that the "open" temp for a Honda thermostat is 175 F. 225 F is too hot; so is 205. You can check the fan by turning on the A/C - it should be on then.

I think it's probably a flow problem. If everything else was OK, temp and RPM shouldn't move together so obviously. Since there's no fan, you're only dumping heat from the radiator without airflow.

My guess is that either the radiator is obstructed, and flow is improving when the water pump spins faster, or the water pump is binding / slipping / not turning like it's supposed to.

While I think that proactively replacing the thermostat and the upper/lower hoses is a good idea, I'm not optimistic this will fix your problem. Since you're not planning to chase it down yourself, I would get it into the shop ASAP and tell them what you've noted here.
 

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I would solve my cooling fan issue 1st before blaming the thermostat. It's very common for fan motors to fail with age. It's not common for a thermostat to fail, unless the coolant has been neglected and your dealing with rust and corrosion.
 

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I would solve my cooling fan issue 1st before blaming the thermostat. It's very common for fan motors to fail with age. It's not common for a thermostat to fail, unless the coolant has been neglected and your dealing with rust and corrosion.
My thermostat lasted 16+ years, not crusty but the seal to the block was compromised as well as the hose connection. SMH...disaster averted again. Not saying this is the issue but besides neglecting coolant maintenance, mixing in different types of coolant can result in a gel-like mixture. The gel-like mixture/coolant can stop normal flow through the system, clogs up passageways, radiator, and the heater core. Like everything else on my TLC I replaced the thermostat with a genUine Honda thermostat $$
 

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My thermostat lasted 16+ years, not crusty but the seal to the block was compromised as well as the hose connection. SMH...disaster averted again. Not saying this is the issue but besides neglecting coolant maintenance, mixing in different types of coolant can result in a gel-like mixture. The gel-like mixture/coolant can stop normal flow through the system, clogs up passageways, radiator, and the heater core. Like everything else on my TLC I replaced the thermostat with a genUine Honda thermostat $$
I've never had to replace a Honda thermostat. I've never mixed coolant, maybe that's why. I've always flushed thoroughly with distilled water before introducing Prestone Concentrate. The green monster keeps my gremlins away. 😁
146296

Just from experience from others bringing vehicles to me for help. Tap water is a cooling system killer.
 
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Discussion Starter · #10 ·
Thanks everyone for your suggestions. Calling the mechanic shortly to see what to do next.
Let me just warn those who have VCM muzzling devices on their vehicles, it was much more difficult to detect while the device was on. So at this point I think it's very important to ensure you get a muzzler that cuts off if the engine reaches a certain high temperature.
 

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Thanks everyone for your suggestions. Calling the mechanic shortly to see what to do next.
Let me just warn those who have VCM muzzling devices on their vehicles, it was much more difficult to detect while the device was on. So at this point I think it's very important to ensure you get a muzzler that cuts off if the engine reaches a certain high temperature.
Respectfully, I dont believe that's the answer. Ensuring our cooling system are functioning properly is. Then install a VCM disabling device.
Simple things we can do..
In the morning, on cold start, do the cooling fans come on when I turn the AC on? If not, you likely have a problem.
After a drive, knowing the engine is warm, when returning home, place the vehicle in park, turn the AC off. Observe whether the cooling fans are coming on and off to keep the engine cool. If not, there is a problem.
 
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Discussion Starter · #12 ·
Respectfully, I dont believe that's the answer. Ensuring our cooling system our functioning properly is. Then install a VCM disabling device.
Simple things we can do..
In the morning, on cold start, do the cooling fans come on when I turn the AC on? If not, you likely have a problem.
After a drive, knowing the engine is warm, when returning home, place the vehicle in park, turn the AC off. Observe whether the cooling fans are coming on and off to keep the engine cool. If not, there is a problem.
All I'm saying is, using a more intelligent device (like S-VCM) is important. I have VCMTuner I which has no override.
Of course making sure the cooling system is working is extremely important.

I'm just saying that is something to watch out for.
 

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Discussion Starter · #13 ·
Mechanic is saying possibly radiator or maybe the cooling fans.

No loss of coolant, white smoke or contamination leads me to believe it is NOT the head gasket but I'm not an expert. But I hope I'm right.
 

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Mechanic is saying possibly radiator or maybe the cooling fans.

No loss of coolant, white smoke or contamination leads me to believe it is NOT the head gasket but I'm not an expert. But I hope I'm right.
If the car
I removed my VCM disabling device today and plugged my scan tool in to monitor the coolant temperature while I was driving today.

While idling after the engine was warmed up, the temp got up to 225. Is that normal? It hovered around 206-208 while driving. This was with no VCM disabling installed during this time.

The coolant level is good in the radiator and the overflow tank. I assume the only other thing it could be is a thermostat?
Any suggestions on how to further test this?

I should add, the fan does not come on when the temperature reaches 200+ which leads me to believe something may be wrong with the fan. Any ideas?

Thanks for you input.
If it cools from 225F to 207 when moving, that looks like one or both fans aren't running when not moving. If you turn on the AC and go look, are they both running?

When the engine cools, open the radiator cap and let the engine warm up, check for flow when the thermostat opens, wait for the fans to come on. Make sure you see good flow in the radiator and there are no leaks or obstructions in front of it, like leaves, snow, dead bodies, missing $100 bills, etc.
 

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Should be able to unplug the fans and connect a separate power source to them to test if they are functional.
Maybe the relay that switches power to the fans has failed?
 

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Should be able to unplug the fans and connect a separate power source to them to test if they are functional.
Maybe the relay that switches power to the fans has failed?
👍👍👍
I stripped these wires with connections off an old central AC unit. They slide over the 2 prongs of the fan connector so I can hot wire to the battery with a quick touch of the posts. You get your answer real quick this way.
146313
 
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Mechanic is saying possibly radiator or maybe the cooling fans.

No loss of coolant, white smoke or contamination leads me to believe it is NOT the head gasket but I'm not an expert. But I hope I'm right.
Have you verified what the factory “efan on temp” is? I’ve owned some GM vehicles in which the efan(s) were triggered “on” at 230F. So, 225F “on” temp may be normal for a 2013 Pilot.🤷‍♂️ There’s probably more airflow thru the rad while driving than efans can pull. Again, check to see what factory “on“ temp is.

What ambient temp while driving?
 

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Discussion Starter · #18 ·
Apparently it was the radiator and the fan. It's had a crack in it for a while and it wasn't causing a big enough problem for me to do anything about it. I kind of forgot about it.

So $700 for the fan and the radiator. Not ideal, but reasonable as far as paying someone else to do it goes.
 

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Apparently it was the radiator and the fan. It's had a crack in it for a while and it wasn't causing a big enough problem for me to do anything about it. I kind of forgot about it.

So $700 for the fan and the radiator. Not ideal, but reasonable as far as paying someone else to do it goes.
Oh man!
We can walk you through a DIY, for way less than that with Denso.
 
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Discussion Starter · #20 ·
Oh man!
We can walk you through a DIY, for way less than that with Denso.
I know....I just don’t have the time to order parts or to fix it. BUT I’ve saved about $800 in the past year doing my own brakes so it cancels it out?🤷‍♂️

It’s a bad feeling knowing you’re paying somebody a big mark up to do something you’re capable of doing yourself....
 
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