Warranty extension for fail-safe thermostat

[SparkYellow]

I see only one coolant temp value in my OBD app.

Is that OBD Fusion? OBD Scanner shows two. Seeing how the two values fluctuate gave me a better sense of the system's health. I also have a rad cap that shows the temp.

 

[stickerbush]

The app I'm using is OBDLink. I'll check again to see if there are two coolant temp values available.

 

[stickerbush]

I checked again and indeed there are multiple PIDs for engine coolant temperature. I will have another look at all of the coolant temp values (there's Engine Coolant Temperature, Engine Coolant Temperature 1, and Engine Coolant Temperature 2.

 

[SparkYellow]

I checked again and indeed there are multiple PIDs for engine coolant temperature. I will have another look at all of the coolant temp values (there's Engine Coolant Temperature, Engine Coolant Temperature 1, and Engine Coolant Temperature 2.

My understanding is that the temp in the engine block stays high unless/until cooler liquid is mixed in from the radiator. The radiator, on the other hand, is equipped with a fan and fins to cool itself down to near ambient temp. I don't understand how the engine temp would drop to 175 at any point during an active drive, is that what CD does? I am not familiar with all the models/trims. Good thing that you're watching the temp closely! Hope the other value will help make it make sense.

 

[stickerbush]

I have some more data on the coolant temperature. This time I captured vehicle speed along with the 2 engine coolant temperature values. Temp 2 generally seemed to track along with Temp 1 but was 10-15 degrees cooler. Maybe Temp 2 is at the radiator and Temp 1 internal to the engine?

You can see that Temp 1 moves up and down in a range of 15-20 degrees. This corresponds with what I see on the gauge in the console. I expect the coolant temperature to remain fairly stable once the engine warms up.

I will likely go back to my dealer with this issue relatively soon.

To recap, my CX5 is a 2024 NA without CD. The thermostat was replaced about a year ago under warranty after exhibiting symptoms similar to what I'm seeing now.

 

[SparkYellow]

I have some more data on the coolant temperature. This time I captured vehicle speed along with the 2 engine coolant temperature values. Temp 2 generally seemed to track along with Temp 1 but was 10-15 degrees cooler. Maybe Temp 2 is at the radiator and Temp 1 internal to the engine?
....

Can you look up coolant temp sensor on the parts diagram for your CX-5? That's how I found out that the second value (for CX-3) was for the radiator.

 

[stickerbush]

Can you look up coolant temp sensor on the parts diagram for your CX-5? That's how I found out that the second value (for CX-3) was for the radiator.

I've looked but unable to find any temp sensors on the parts diagrams.

 

[N7turbo]

Logically speaking, for me, I would want to see coolant temperature before and after the radiator. So it's possible that's what they are.

 

[SparkYellow]

I've looked but unable to find any temp sensors on the parts diagrams.

They call it water temp sensor.

18840C.

One is on the driver side of the engine near 15-17Z the water control valve. The other is on the passenger side near 15-010 the water pump. I may be looking at the wrong diagram though, there are variations between US/Canada and Mexico, with or without CD.

 

[Jmaz]

On my 2014 the coolant temp#1 is the normal engine coolant temp and temp #2 is the temp of the coolant exiting the heater core. The sensor is at the firewall on the passenger side. With the engine hot and at idle, with heat selected (no a/c on) and with the heater fan off, both temps track close. Turning the heater fan on will decrease temp#2 as heat is removed from the coolant passing through the heater core. I've actually had them reading within 1 degree of each other. Lets me know my heater core has no blockage.

 

[stickerbush]

The question I have is should the coolant temperature as indicated by the gauge in the console remain relatively stable once the engine has warmed up? By "relatively stable" I mean 5 or 10 degrees, not 15 or 20 degrees.

My experience with our new 2024 is that coolant temperature remained very stable until it didn't, at that point the dealership diagnosed a bad thermostat and replaced it. Temperature stability returned and stayed that way for almost a year before it became unstable again. Measuring coolant temperature via OBD shows it moving up and down in a range of 20 degrees or so under normal driving conditions. I don't think this is normal.

 

[SparkYellow]

Your charts for the stats at lower speed show a lot of fluctuation that don't really match the slight changes in speed. It went high up to 198 or so when the speed was still under 40. The dip to 170 in the middle also isn't justified.

Temp 2 at the water pump is lower for pulling cooler fluid from the radiator. Temp 1 is higher at the control valve before releasing hot fluid back to the radiator. The thermostat sits inside the control valve. It is not clear to me how the thermostat is responsible for the frequent and drastic up and down. The temps do track with each other so both sensors can't be faulty. The fluctuation can't be caused by anything between the pump and the control valve? The trip through the engine only leads to the difference between two temps.

It looks like the radiator/fan is erratic? The traditional thermostat fault that I am aware of, is stuck open or stuck close. I am not familiar with a thermostat that opens and closes so frequently and erratically. It sounds like electronically controlled behavior (gone rogue). So if the thermostat is stuck open (because the temp gets low), the control valve loses its mind.

 

[SparkYellow]

The two values on the CX3 are like this. Temp 2 (water B) is at the radiator. Temp 1 stays above 194 and below 214.