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Discussion Starter · #1 · (Edited)
Hi all, I'll preface this post with a disclaimer that I have very little experience working on cars...so please bare with me! My pilot also has a bad VSA module which I have chosen not to replace, as well as some issues with the TPSM system...so my maintenance light being on a normal occurrence.

Yesterday morning on the way into work I first noticed that I was getting no heat from the air vents...and after a short while of driving my temperature gauge pinned out. I was able to make it to work without noticing any odd sounds/smells. On the way home I experienced the same issue. I attempted to keep it under 2000-2500 to minimize the overheating, but before I could quite make it home my emissions/engine light came on. I drove a bit further and nearing my house on a longer downhill slope I shut the engine off to try to cool it down and when I tried to start the car back up at the base of the slope it chugged/smoked and I shut it off there and towed it the rest of the way.

I plugged in my cheap OBD reader and the car is throwing a P0117 Engine Coolant Temp Sensor Circut Low Input code. The coolant reservoir was somewhat low, but not empty, so I topped it off to the max fill line. After the car had cooled down I was able to start it up without any obvious issues. I also checked the oil level and although it's dirty, it seems to be okay.

So there's the backstory...and now I'm not entirely sure how to move forward. Some questions I have after doing some research...

  • If the ECT sensor(s) are bad, would that explain the lack of heat coming from the air vents? I assume if the coolant is not circulating because the ECT is not telling it to...that would mean there is no heat to pull into the heating system?
  • Could it be thermostat related? How difficult is that to replace?
  • Water pump?
  • Any recommendations on where to start troubleshooting?
A co-worker suggested that I double check the coolant level and make sure there's no coolant/oil mixture by opening up the radiator and looking for off-color coolant. I did not open up the radiator cap yesterday to double check the coolant levels, but I have not noticed any leaks in my driveway/garage so I don't think the coolant is leaking. I will check the coolant in the radiator this evening.

I think I am comfortable replacing the ECT sensors, they don't look too hard. I think I can also handle draining/refilling the coolant. Need to do some more research about burping the system. If it's something related to the thermostat I'm not sure I want to dig into that. If it's the water pump it seems like that is integral to the timing system and I'm not going to touch that one myself!

Any help you can offer and/or resources to point me to would be greatly appreciated! I'll search around for similar threads in the meantime.

Thank you!
Lane

Edit: 162500 miles on the car and the previous owner indicated that the timing belt was replaced per maintenance schedule. I am the second owner and the only other owner was an elderly couple that I'm lead to believe took good care of the car.
 

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Hi, and welcome to the forums. Hopefully you didn't continue driving too much while overheating to cause further problems.

Maybe it's just a leaking radiator, so WHEN IT'S COLD check inside radiator cap for coolant level and color, hoping you don't have the dreaded strawberry milkshake of coolant mixing with ATF. If the coolant level is just low, you might have just a hairline crack on you rad, and it's not going to get better, so you might want to do what I did when I changed the radiator and also get new hoses and thermostat while you're at it. Even if you don't DIY it, you can get good parts for a good price at Rockauto.com and have a trusted mechanic do it, rather than a scandalously overpriced dealer. Get a Denso or a TYC.

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Since your not mechanically inclined. You need to get to a well rated independent mechanic before running it again. "Chugged and smoked" after pegging the temp sensor twice is very concerning.
 

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Discussion Starter · #5 ·
When's the last time you've flushed the coolant and changed the thermostat?
I've had the car for about 3 years. I don't believe I've had the coolant flushed in that time. Neither have I changed the thermostat. Timing belt had been done per maint schedule per the previous owner.
 

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Discussion Starter · #6 ·
Since your not mechanically inclined. You need to get to a well rated independent mechanic before running it again. "Chugged and smoked" after pegging the temp sensor twice is very concerning.
I appreciate that, and I definitely will... Just hoping to do some troubleshooting and replacing of cheaper/easier components before I take it in.

I wouldn't say that I'm not mechanically inclined, just that I don't have much experience with cars or engines.
 

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I've had the car for about 3 years. I don't believe I've had the coolant flushed in that time. Neither have I changed the thermostat. Timing belt had been done per maint schedule per the previous owner.
I would start with the flush, cleaning the coolant temp sensor, and replacing the thermostat. There could be rust in the coolant that could be causing the thermostat to get stuck and dirtying your Engine Coolant Temp Sensor so check for discoloration on the coolant.
 

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Discussion Starter · #8 ·
Hi, and welcome to the forums. Hopefully you didn't continue driving too much while overheating to cause further problems.

Maybe it's just a leaking radiator, so WHEN IT'S COLD check inside radiator cap for coolant level and color, hoping you don't have the dreaded strawberry milkshake of coolant mixing with ATF. If the coolant level is just low, you might have just a hairline crack on you rad, and it's not going to get better, so you might want to do what I did when I changed the radiator and also get new hoses and thermostat while you're at it. Even if you don't DIY it, you can get good parts for a good price at Rockauto.com and have a trusted mechanic do it, rather than a scandalously overpriced dealer. Get a Denso or a TYC.

2005 HONDA PILOT 3.5L V6 Radiator | RockAuto

Don't forget to enter your PIloteer's discount code when you order.
Hi thanks. I also hope I didn't drive too far!

I'm looking in the radiator now and I think the coolant level is low...I only see fluid resting on top of the dips in the fins on top. The coolant resting on those fins is a milky yellow color vs the translucent yellow of the coolant in the coolant reservoir. I can see a short ways down between the fins and I don't see any liquid.

I'm thinking I should top it up? I'm going to go eat dinner and come back after. Maybe someone can save me some trouble between now and then if I should not fill it before draining or something like that. :)
 

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Discussion Starter · #9 ·
I would start with the flush, cleaning the coolant temp sensor, and replacing the thermostat. There could be rust in the coolant that could be causing the thermostat to get stuck and dirtying your Engine Coolant Temp Sensor so check for discoloration on the coolant.
Thank you. As I just posted it seems like my coolant is quite low. I don't see standing liquid in the radiator except for a slight amount of milky colored yellow resting on top of the fins. Like less than a quarter of an inch deep and I don't see any down in the fin slots.

134637


134638
 

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Best case scenario, you just have a coolant leak. Don't drive it anymore and have it towed to a trusted mechanic to change the radiator, hoses and thermostat.

But before doing that, the usual Honda coolant is blue, and that's what makes the strawberry milkshake of coolant mixing with the ATF. If you've been using yellow coolant, it may make a different color milkshake when mixed with ATF, perhaps the "milky" yellow you're seeing. In that case, sorry to say, you may have serious transmission problems, which sometimes can be fixed with a 3x ATF drain & fill (not flush) and driving it around a bit between each. Do this after you've changed the radiator, etc., if you're willing to gamble that will fix it, as it occasionally does, but in many cases, if you've driven it too far after the mix occurred, the transmission is ruined and only a replacement transmission will fix it.

There's also the possibility that you you've overheated your engine to the point of damaging it.

Hate to be the bearere of such dire news, and you can try the easier and less expensive suggestions above first, and hopefully it won't be the transmission and/or the engine. But do have it towed to a trusted mechanic and checked out.
 

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I have dealt with the ECT (engine coolant temp sensor) issue for two months last summer/fall. Hopefully, this helps--https://www.piloteers.org/threads/whats-best-coolant-temperature-sensor-brand-for-2005-pilot.164245/
 

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Discussion Starter · #12 ·
Updates:

I attempted some diagnostics over the weekend, got all ready to flush the coolant and refill. I didn't get that far though because the first thing I tried was just to see if the system would even hold liquid and if it would overheat with the coolant full. Poured some left over coolant in and pretty much immediately it began to leak out of the passenger side somewhere that I couldn't see. Looks like it's coming out somewhere behind the timing belt...best guess is the water pump.

The mechanic I had look at it determined the same thing. I am wondering if the water pump was not serviced when the timing belt was done the first time around...no real way for me to know now.

So now I'm faced with a decision. Mechanic quoted ~$850 to fix water pump...haven't clarified if that includes a new timing belt also, since we might as well just get that done at the same time.

My dilemma is...I don't know if I borked up the engine while driving it overheated and I really can't afford to sink $850 into the car if the engine is bad anyway. Mechanic says he can't really tell I warped the head unless it's full of coolant and he can run it up to temp...which makes sense to me.

Are there any tests we can run to know if the engine is permanently damaged? I will say that the car starts up just fine, and sounds okay while it's first heating up.
 

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For $50, it may be worth replacing the ECT (engine coolant temp). It's a long topic that I posted a few months ago but if you copy and paste the one I posted above, it may be worth considering. Issues like these are like trying to catch your tail. It's a process of elimination, sometimes. Thanks.
 

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Discussion Starter · #14 ·
For $50, it may be worth replacing the ECT (engine coolant temp). It's a long topic that I posted a few months ago but if you copy and paste the one I posted above, it may be worth considering. Issues like these are like trying to catch your tail. It's a process of elimination, sometimes. Thanks.
I would definitely do that, but at this point I don't think it's a viable option. I believe I'm getting the ECT codes because there is no coolant flowing across the ECT sensors...because it's all leaking out of the water pump area before it even gets there.
 

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To check the head gaskets, you could have each cylinder tested to verify that the combustion chamber holds pressure at Top Dead Center. Set a cylinder to TDC. Then remove the spark plug and replace with pressure gauge that also allows you to pressurize with compressed air. Pressurize to 150 psi. A good cylinder will hold pressure. A bad head gasket will leak down to an adjacent cylinder. A good mechanic should have the tools to do this without replacing the water pump, etc.
 

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TROUBLESHOOTING DEAD CYLINDERS
INFRARED THERMOMETER

A good way to do this is with a noncontact infrared thermometer such as Raytek's Raynger ST that measures heat energy radiating from the thermostat housing. An ordinary contact thermometer relies on surface conductivity to take a temperature reading. Consequently, it is slow and may not give an accurate measurement if there is poor contact between the thermometer and thermostat housing. But a noncontact infrared thermometer does not rely on direct physical contact. It measures infrared heat energy radiated from the thermostat housing and gives you instant results. Note: The accuracy of an infrared temperature reading depends on the reflectivity (emissivity) of the surface.

Some problems such as engine misfire can be time-consuming to troubleshoot. Isolating a misfire to a specific cylinder usually requires a power balance test (which is not easy to perform on some of today's distributorless ignition systems) or observing ignition patterns on an oscilloscope (which requires an expensive scope and making the necessary hookups). But now there is an easier way. Just use an infrared thermometer to measure and compare the temperature of the exhaust at each exhaust port. A misfiring cylinder does not produce as much heat energy as a good cylinder, so the exhaust from a weak cylinder will not be as hot as that from cylinders that are firing normally.


To find the misfire, aim the gun at each exhaust port on the manifold and squeeze the trigger. Note each reading and compare the results. Any cylinders that are misfiring will read significantly lower than the others.


Once you have identified the misfiring cylinder, you can zero in on the underlying cause. Remove and inspect the spark plug. If wet, the plug may be misfiring because of a bad plug wire, cracked distributor cap or bad coil on a DIS system. If the spark plug is fouled, the cylinder may have an oil consumption problem due to worn valve guides and/or rings. If the spark plug appears to be okay, the air/fuel mixture may be too lean. Check for a dirty or inoperative fuel injector, or an air leak around the injector seal. On older engines with carburetors, check for intake manifold air leaks. Another possibility may be a leaky valve. Check compression.


This same procedure also works great on diesel engines. Reading and comparing exhaust temperatures can help to identify weak cylinders and diesel injector problems.
 

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