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Discussion Starter #41
No issues with coolant spilling over the top of the tranny. I did rinse it off with a slow stream of water after I completed the job.

I guess next time I’ll try the engine block drain ports. I was paranoid I wouldn’t be able to tighten them back up correctly and they would leak. Or that I would break one off and be really screwed.

What is the direction of coolant flow? I would guess engine to top hose to radiator to bottom hose to thermostat back to engine block. That would support the lower hose being cooler than upper hose after a long drive.
Oops, you’re right, i got the direction of coolant flow reversed, lol. thanks!
 

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They are not that bad: just a 14mm bolt head IIRC and a 1/4" hose connection which you put a silicon hose on. As they are in soft aluminum, they seal easily.
 

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Discussion Starter #43
Just installed the new thermostat on my 05 Pilot! Very tight in there. Forget about seeing the bottom bolt--there is a bunch of wiring harness that also impeded access. But you can feel your way to it. The radiator drain cock was also hard to access and difficult to open without breaking it--I didn't drain the coolant. So I ended up pulling the bottom hose that attaches to the thermostat (a quart of coolant spilled) and when I finally pulled out the thermostat, about a gallon more spilled (I was ready for that with a basin under the engine to catch it. The more important thing is the positioning of the O-ring when fitting it to the thermostat. Also the position of the new thermostat itself when replacing the old one. There is a sort of a nipple (the color here is white but it actually is a brass) that must be pointed up and the O-ring nub must be align with this nipple. As you insert the thermostat pointed up in to its house, the O-ring nub will fit into a notch when place into the thermostat housing. Make a mental note of how these two is oriented when you pull out the old thermostat in relation to the housing. Also make sure the thermostat with the O-ring fit snuggly into the housing before you screw in the cover where the hose attaches to. Thanks!
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Discussion Starter #44
I have replaced the coolant temp sensor and the thermostat! The code below keeps popping up! Anyone had this issue before? The last sensor that links to this problem is the internal air temp (IAT). Thanks.

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Does your code reader report the coolant temperature? Can you compare that value to an IR thermometer reading near the sensor location?
 

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Discussion Starter #46
It does. The highest temp (after running for 15 min at hghway speed) is between 180-183 F. I don't have an IR thermometer. But I replaced the sensor already. Hmm, could be the wires, right?
 

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Discussion Starter #47
Below is how to do an initial test of IAT with scan tool. So the scan tool shows IAT temp at 84F with the ambient temp at 75F. That is not a glaring difference, right?--"After turning it on, check for the temperature of the IAT sensor. It should be 10°F above or below the ambient temperature of the vehicle. If this is not the case, you may have a problem with the sensor."
Testing an IAT Sensor
Testing for a faulty IAT sensor is not very difficult, and requires only a scanning tool, a multimeter, and a wire piercing probe. This process is inexpensive, and is always a good idea before going in for a replacement. To use the scan tool, you need to perform the following steps.
  1. Attach the scan tool to the vehicle, and turn on the engine.
  2. After turning it on, check for the temperature of the IAT sensor. It should be 10°F above or below the ambient temperature of the vehicle. If this is not the case, you may have a problem with the sensor.
  3. Shake the IAT sensor connection to the mass air flow sensor, and check to see if there is any difference in reading. A change in the reading indicates a bad connector, which then has to be replaced.
  4. If the temperature reading displays -30 to -40°F, the dashboard light should show the code P0113, and if the reading displays 300°F, the dashboard should show the code P0112.
  5. If the reading shows a temperature of 300°F, you need to check if the MAF sensor wires are shorted because of the internal copper getting exposed to each other. Remove all electrical tape to examine the wires and check for signs of damage.
  6. Separate the shorted wires and check if the readings turn normal; if not the connector needs to be replaced.
  7. Disconnecting the IAT from the MAF should get the temperature reading back to -30 to -40°F. However, if this does not happen, it means that there could be a problem with the vehicle's internal computer, which needs to be checked and solved by a technician.
  8. Connecting the 2 IAT wires with jumper cables should change the temperature to 300 °F. If this does not happen, it might mean that the wiring or the computer is bad.
  9. Now, to test the IAT sensor with a multimeter, you should measure the resistance of the sensor. If the multimeter shows a reading of 0 to 47 Ohms, then you have a problem with the sensor.
 

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If your scanner reports ~180F then like the wire to the sensor isn’t broken. You could disconnect the sensor and see what the scanner reports . . . it should be nonsensical since the sensor is disconnected. If after reconnecting it you start getting reasonable values again the wire isn’t bad. The new sensor you bought might be faulty.

Might be time to invest in one of these to help get to the bottom of the issue.

 

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Discussion Starter #49
If your scanner reports ~180F then like the wire to the sensor isn’t broken. You could disconnect the sensor and see what the scanner reports . . . it should be nonsensical since the sensor is disconnected. If after reconnecting it you start getting reasonable values again the wire isn’t bad. The new sensor you bought might be faulty.

Might be time to invest in one of these to help get to the bottom of the issue.

That might actually make sense! Would it be simpler then to just put the old sensor back? I was actually thinking of doing just that but forgot to do it after I read about the IAT. Thermostat is new so that's out of the equation here. Thanks!
 

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For $20 I’d bite the bullet and get the IR thermometer. Even if you don’t end up needing it for this effort you’ll have an additional troubleshooting tool in your stock for future debugging.
 

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Discussion Starter #51
I agree! Placed the order now. Also has many uses around the house--oven, a/c, etc. Thanks.
 

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Discussion Starter #53 (Edited)
The new coolant temp sensor seemed to be the culprit! I changed the old one before I changed the thermostat. The CEL kept popping back despite changing the coolant temp sensor (first). So I then changed the thermostat! I should have listened and replaced (or even check it) the thermostat first. Also, upon my initial search, I did not do my due diligence--it was suggested that the most common cause of "Temperature below thermostat regulating temperature" is, duh, thermostat followed by coolant temp sensor. Also it was suggested that the lower hose should be near or as hot as the upper hose after driving for several miles! In my case, the lower hose was still cool to touch. So after putting back the old coolant temp sensor this morning, drove it for several miles, the lower hose is as hot as the upper hose. road2cycle is correct! It's the new coolant temp that is bad! But I learned not to celebrate too early! My confidence is so low right now. I will have to see after several days if the CEL will come back ( tho I doubt this since the lower hose has the correct temp now--waiting for IR thermometer to confirm this). Now, if I could only find where I left 3 of my open wrenches...
 

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We all live and learn. The important thing is you kept going instead of throwing in the towel. It’s a good learning experience, especially since you’ve thought through the steps you’ve taken and considered what you would do differently next time.
 

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Discussion Starter #55 (Edited)
This CEL (code PO128) got me well acquainted with my 10 year old scan tool! I learned to read (and erase) codes and live data as well as how to get rid of the "not ready" (they show as "INC"--incomplete) monitors. It's like attending a $50 class (the cost of coolant temp sensor), lol! Oh, btw, the evap monitor keep showing "not ready" status (INC). Upon searching (for the umpteenth times), I just found out this--"2000 and newer model year gasoline powered vehicles will need all emission monitors in READY or COMPLETE status, with the exception of the EVAP monitor. An incomplete evaporative monitor will not cause a smog check failure. It will be the only monitor allowed to be incomplete on a 2000 & newer gasoline powered vehicle."
 

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Discussion Starter #56
Soo, I finally went ahead and did the VEIP 3 days ago! I passed it! There has been one code that kept popping up. Despite driving it for almost 200 miles and no code, "Temperature below thermostat regulating temperature" came on again followed by CEL! This drove me crazy for two months. Then our neighbor who had borrowed my scanner a few times in the past told me that there are two sensors-one is a sending unit. I googled it and found it. I changed that sensor and cleared the check engine light. But the evap system monitor (see pic) remained "inc" (not ready) and I hesitated to take the emission test hoping that it will go away after several normal driving cycles. I google this and found that year 2000 and newer cars can still pass with the evap system monitor incomplete as long as no check engine light. Attaced are pictures of the two engine coolant temperature sensors (I will call them ECT #1 and ECT #2). ECT #1 is on top radiator hose next to EGR valve and ECT #2 is on the thermostat housing. This fooled me for the longest time knowing that there was only ECT #1. So, after replacing the ECT #2, "Temperature below thermostat regulating temperature" no longer came on on the scanner. So is the CEL! But I'm still keeping my fingers crossed. My confidence is still not intact, lol!
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