With the onset of cold weather (25 f), I noticed a very slow warming up of the engine; while driving on a cold engine, the temperature on the display began to drop down to zero.I found out that on a cold engine, during warming up, the upper pipe leading to the radiator began to heat up - it became obvious that the thermostat was stuck in the open position and was allowing the cooling liquid on the sterling engine to flow in a large circle through the radiator, which prevented normal warming up of the engine. The car is a 2019 with 25k miles. I found information that the average service life of this thermostat is 5 years (instead of 10 years lifespan of usual thermostat). Before this, I never had problems with the thermostat on previous cars of different brands. It seems the reliability of this brand is turning into a myth. Acura is following the path of German manufacturers by introducing parts with programmable wear. it's a shame p.s. no any error codes has been found, cooling liquid level is ok, too.

 

Curious how you determined that average life span of thermostat in RDX is 5 years? This is the first failure I am seeing reported here.

 

[QUOTE=russianDude;16915442]Curious how you determined that average life span of thermostat in RDX is 5 years? This is the first failure I am seeing reported here.[/QUOTE

I analyzed similar cases, one of which was described on this forum, and came to the conclusion that the quality factor of the thermostat device had deteriorated, including from my own example. Information was also collected through dialogue with technical staff of service stations. At the same time, the number of requests regarding a faulty thermostat increasedboth owners of Honda cars, and, what is noteworthy, often official dealers position the malfunction of the unit as the increased “energy efficiency” of the power units of the brand’s new models. Having examined the design of the thermostat in more detail, it became obvious that the design was cheaper and the quality of the materials used was lower compared to designs of previous generations. However, I express my personal investigation results

 

Thermostat should be covered under your powertrain warranty.

 

Actually, I saw somewhere that the thermostat may not be covered in the powertrain warranty. I don't have the warranty booklet, and cannot find the info on the internet, so I am not sure. If my wife's goes bad and the fix isn't free, I'll just do it and use an aftermarket part which should last longer.

 

If true, its sad, but still not common occurrence yet. Replacing thermostat could be expensive due to lots
of labor. What are the prices?

 

My 2020 RDX has also been very slow to reach normal temperature in the past winter. I immediately suspected an open thermostat, but eventually ruled that out because I realized that once the normal temperature was reached, it stayed there, fairly steadily. I also noted that in the summer the temperature always reached normal fairly quickly, and remained stable at that temperature no matter how hot the weather was. This was also true this past summer.

I attributed the slow winter warm up to the efficiency of the 4 cylinder engine. I did notice that if I let the engine idle in the garage, the temperature rose slightly faster, which may have been caused by less airflow through the radiator and around the engine. Of course that should not have any effect if the thermostat was closed and not allowing coolant to flow into the radiator.

I was going to change the thermostat myself, as it used to be a 10 minute job in cars from 20 years ago. Unfortunately I could not identify it's location on the engine.

How did your RDX handle the hot summer temperatures? Did it seem to run cool when driving at higher speeds (with more air flow).? Do you have any idea where the thermostat is located on our engines?

Please keep us up to date with any updates you may have.

 

I think that the thermostat is just above and to the left of the ATF fluid warmer, which the maker of this video is taking off (taking off the warmer, not the thermostat). If you back up to the beginning of the video, you can see what has to be taken apart to get to it. Some coolant systems are difficult to purge all of the air when drained. I have no idea of the "burping" procedure or difficulty on the RDX 2.0T cooling system.

 

I just looked at my wife's RDX, and I think that you could actually replace the thermostat without removing all that stuff above. That electrical connector should be disconnected and moved out of the way, and a bit of contortion may be required. I think an experienced mechanic could do it in 20 minutes, plus whatever time is required to drain/refill the coolant.

Here's a photo:

 

Thanks for that info. Now that you point it out, it seems pretty obvious that this is the thermostat, being that it is attached to the radiator hose.

I will look under the hood later today and determine if it is something that I would be willing to tackle. I wouldn't mind spending a few dollars on a new thermostat if there was any chance of getting faster warmup times.

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My experience with dozens of cars between myself, my wife and working on my families cars is that the thermostat is one of those parts that might last the lifetime of a car or go anytime it feels like it. This includes the major JDM brands, American and German cars. Keep in mind, no one makes their own thermostat, the manufacturer buys them in bulk and throws them in. No pre inspection. So bottom line, your thermostat going bad is not an Acura problem.

Dont get your panties in a bunch over a $25 part.

 

I had a look under the hood, and I was able to locate it. It would have been difficult to see without the help of the video and image. It should be pretty easy to do the job after taking out the air box and associated parts, which I have already done in the past. I also noticed a petcock at the bottom of the radiator, and a cutout on the plastic "skid plate" to allow easy draining.

It looks like the thermostat comes as an assembly with the housing. Does it look like the correct part is the "Cover Assembly, Thermostat" in this LINK?

​​​​Now I just have to find the torque ratings of the 3 bolts, and the burping procedure. I'm also hesitant about starting the job in below freezing temperatures, in case the simple job turns into a $hit show.

Let me know if you decide to do your own replacement, as that would provide the encouragement I need. 🤣

Thanks for your help.

 

I'd give it a shot first to replace it without removing the airbox, etc. A small ratchet driver and just the right extensions should make it possible. Unless you need to replace your engine air filter anyway.

 

I just found an image of the thermostat on Ebay, which confirms that the housing and the thermostat come as an assembly.

LINK

What I really like, if you zoom in on the bottom of the assembly, is that it appears to use an O-ring rather than a paper gasket. That makes it almost impossible to leak, which was my main concern in using paper gaskets.

Since you are located in the SF Bay area, you probably have no idea how miserable it is working in below freezing temperatures, and even worse if you have to do the job a second time because of a leak.

BTW, if I do order a thermostat I will order a genuine Acura part on-line, or pick it up at the dealer. I was only searching Ebay hoping to see a better image of the part.

 

Today I replaced the thermostat with a new one, replaced the coolant, and charged the battery. subjectively - the car began to warm up somewhat faster but still not as it was at the very beginning... And the problem remained related to the floating engine temperature...The another problem is that my engine gauge has been fluctuating up and down while warming up, till driving … Sometimes it shows 1/8 - go back down to 0, then come back up, etc.I found another topic here - where the owner had a problem with long warm-up and floating temperature... in his case it turned out that the culprit was the sunlight sensor which affected the air conditioning system... after replacing it, according to him, warming improved noticeably and the engine temperature stopped fluctuate … but I can’t find the error of this sensor or unit during car selfdiagnostics.... Also, may be the problem is with cooling temperature sensor ? But it was no 0128 error code has been found ….


here is the topic … https://acurazine.com/forums/3g-rdx-...-gauge-985345/

 

Congratulations on changing the thermostat yourself. I would be interested in any difficulties you may have encountered.

I'm not sure what you mean by "the problem remained related to the floating engine temperature" as I don't recall you mentioning that in your OP.

The rapid rise and fall of the gauge, is often a symptom of air pockets in the system, which is common after draining the fluid, and why "burping" the system is often difficult. As warm coolant flows past the sensor, the gauge shows normal, but then an air pocket moves past and the temperature drops, or sometimes vice-versa..

I have my doubts about the sunlight sensor causing the problems you mentioned.

I do know that the sunlight sensor is used to turn on the headlights as it gets dark (or when driving under bridges), so if your automatic lighting system is still working properly, I wouldn't suspect a faulty sunlight sensor.

My 2016 RDX used the GPS to recognize when I was heading south (towards the sun), and increased the blower speed. Perhaps the 3G models still do this, or maybe they have switched to using the sunlight sensor to boost the AC when the sun is brighter. But fluctuating blower speeds was not mentioned in the other thread.

I have read that the AIS will not activate when the HVAC system is requesting maximum cooling or heating. But it is pretty obvious when the maximum is occurring (i.e. maximum blower speed). If the blower was continuously operating at full speed, I would be complaining about the HVAC system and not the AIS.

My AIS has become disabled a few times now. I'm not sure exactly why, but possibly related to starting the engine while the hood was opened. I have been able to restore normal operation each time, by disconnecting the battery for a few seconds.. That is most likely what fixed AIS in the other thread.

 

I had a look at the Live Data that was available on the RDX using my Anyscan A30M tool. LINK.

It looks like there are 2 Engine Coolant Temperature (ECT) sensors. I can't be certain, but I think one might be used by the gauge and the other is used for engine management. I can't explain why one of them reads much higher than the other . This screenshot was taken only a minute after starting the engine with an ambient temperature of about 2'C (Canadian). If this is the case, then monitoring this data to see if it also fluctuates may help in your diagnosis.

There is Live Data also available from the Body Control Module (BCM), Lighting section, which shows the signal from the Automatic Lighting Sensor. Monitoring this would also help in your diagnosis.


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Thank you for the valuable information, another confirmation of a possible problem with the solar light sensor installed in the cabin giving false readings. After replacing this sensor I will report the results

 

On hot days the engine temperature is stable and no problems have arisen. But, I saw an error in automatically switching the display to day/night mode. I guess that this is a problem with the solar sensor based on the previously described example of the owner, who, due to a malfunction of this sensor, had problems with the efficiency of warming up the engine and the floating temperature of the coolant. Having replaced the thermostat yesterday, I noticed that subjectively the heating efficiency has improved somewhat, but the problem has not completely gone away. Having placed the old thermostat in a pan and brought the water to a boil, I noticed that the thermostat opened, so this fact suggests that most likely the problem is not in the thermostat itself

 

Thank you for the valuable information, another confirmation of a possible problem with the solar light sensor installed in the cabin giving false readings. After replacing this sensor I will report the results

 

the fact is that in case of air jams in the cooling system, as a rule, it does not work properly (cold air blows from the interior heating vents) - but it works without complaints. in addition, the coolant was replaced which may be ( moy sure) should have solved the airlock issue, and the cooling system diagnostics at the service center showed no problems... but, I will take your advice and check for an airlock again.

 

the fact is that in case of air jams in the cooling system, as a rule, it does not work properly (cold air blows from the interior heating vents) - but it works without complaints. in addition, the coolant was replaced which may be ( moy sure) should have solved the airlock issue, and the cooling system diagnostics at the service center showed no problems... but, I will take your advice and check for an airlock again.

 

After changing the thermostat, I’ve found mistakes in diagnostic mode - the problem was 0x4d07 code - that code seems have not been the regular service code - it’s the program issue code that provided with info that there was a signal disconnection between the metric device (temperature sensors ? There a two of them - in radiator and engine ) … I’ve rebooted car to factory, scanned the ICU with Ktuner - and seems like the problem was gone with strange temperature fluctuations ….

 

Those are probably the 2 ECT sensors my code reader displayed in my earlier image.

The RDX had been sitting in the garage for at least 8 hours, in an ambient temperature of about 2'C, and one sensor read 7'C after the engine had been running for a couple of minutes (a reasonable value) while the 2nd sensor read 29'C (a warm summer day). I will monitor these sensors while driving to make sure they are both reporting updated values, and not just stuck at a fixed value.

I would think that the radiator temperature sensor would just be used to turn on the radiator fans, while the second sensor would be used for engine management, and likely the dashboard gauge. I'm not sure how either one could affect the actual heating rate of the engine, since the thermostat seems to be strictly old-school mechanical and not computer controlled.

Could you explain this "diagnostic mode"?. Is this a mode in your OBDII code reader, or a RDX built-in function?

 

it’s build-in system diagnostic option you can log in when you press and hold three buttons of your sensor panel - there - you can initiate diagnostic process by choosing the directory. I should agree that the thermostat might be not the case - the old one opened up during boiling it in a hot water under 78 C

 

So thermostat is not the issue? What is the issue then?