Intermittent Coolant Sensor Issue

[Lagonia]

I have been having this for a couple of months now but I would almost bet this has nothing to do with the thermostat. My symptoms are classic: Randomly the temperature readout will be ---F, the radiator fan will kick in and A/C compressor will turn off (if on). Sometimes the CEL goes on with P0128, sometimes it does not; the temperature readout will turn on again at random times and the engine temp will be exactly where I would expect it to be. I set my DIS to display temperature all the time now. Note that I have no problems with drivability whatsoever when this happens.

I have just replaced the coolant sensor this morning and getting ready for a 500 mile trip this weekend. Will see what happens.

[Lagonia]

Yeah, ok, replacing the temperature sensor did not help. It took about 450 miles, several drive cycles but it came back. When the temperature readout goes to ---F, it does not mean that the temperature sensor is bad. I hooked up my scan tool to find out that the temperature is logged correctly. After I stop the car and turn the ignition on, the temp indicator will still be ---F. The moment you clear the codes using the scan tool, the temperature readout resumes. So, basically, the ---F is set by the ECM when the P0128 is either set or is pending. I stand corrected, next step will be replacing the thermostat.

[Dave@ddmworks]

Originally Posted by Lagonia Yeah, ok, replacing the temperature sensor did not help. It took about 450 miles, several drive cycles but it came back. When the temperature readout goes to ---F, it does not mean that the temperature sensor is bad. I hooked up my scan tool to find out that the temperature is logged correctly. After I stop the car and turn the ignition on, the temp indicator will still be ---F. The moment you clear the codes using the scan tool, the temperature readout resumes. So, basically, the ---F is set by the ECM when the P0128 is either set or is pending. I stand corrected, next step will be replacing the thermostat.

We had a car in recently, same problem. The owner had just bought the car, and we could tell that the thermostat had just been replaced, we pulled the thermostat to check it in boiling water, everything appeared fine. We replaced the sensor with an extra sensor we had around the shop that we knew was good, but the code still came back. We replaced the thermostat with a GM one, the code stayed away and has not come back. Not saying that it has to be a GM thermostat, the one we replaced could have just been bad from new, but we always put new GM thermostats in all of the engine builds we do.

Hope that helps,
Dave

[info2x]

Dave checking the stat in boiling water is not an ideal test. The stat is designed to begin opening at 82C IIRC, if it starts to open before that the stat could set the CEL. The stats also have a very low leak rate so if the stat is leaky you can set this code as well.

Same code can be set if the sensor becomes stuck below a certain temp or is biased low enough.

[Dave@ddmworks]

Originally Posted by info2x Dave checking the stat in boiling water is not an ideal test. The stat is designed to begin opening at 82C IIRC, if it starts to open before that the stat could set the CEL. The stats also have a very low leak rate so if the stat is leaky you can set this code as well. Same code can be set if the sensor becomes stuck below a certain temp or is biased low enough.

I absolutely agree, but we wanted to make sure that it was opening and closing atleast.

Since we have been using the OEM thermostat's we have not had any issues.

[info2x]

Good stuff. Just making sure we're all on the same page.

[OSUCherokee]

man...I really don't want to try to replace my thermostat... But it looks like that is the general culprit here. Hoping I don't have to take off much, if any of my supercharger parts.

[Carbon Sky]

Originally Posted by OSUCherokee man...I really don't want to try to replace my thermostat... But it looks like that is the general culprit here. Hoping I don't have to take off much, if any of my supercharger parts.

Considering the supercharger stuff is at the front and the t-stat is at the back, unless the t-stat is tapped for coolant (which I'm doubtful of with it being a supercharger and not a turbocharger that is much more likely to be liquid cooled), there shouldn't be any supercharger stuff in the way.

Don't be tempted to not remove the plastic cowling. It's worth the trouble. I couldn't see doing a t-stat on the kappa with the cowl in place. At least not with my hands.

Good luck!

[OSUCherokee]

Originally Posted by Carbon Sky Considering the supercharger stuff is at the front and the t-stat is at the back, unless the t-stat is tapped for coolant (which I'm doubtful of with it being a supercharger and not a turbocharger that is much more likely to be liquid cooled), there shouldn't be any supercharger stuff in the way. Don't be tempted to not remove the plastic cowling. It's worth the trouble. I couldn't see doing a t-stat on the kappa with the cowl in place. At least not with my hands. Good luck!

Is it easier to reach from above or below?

[Carbon Sky]

I did it from above. Not sure if it would be easier from below but I doubt it.

Not sure if this will help, but the t-stat housing is in the middle of the picture in the background.

[Jackknife]

Some '06 Sols have an oil cooler attached to the back of the engine (mine does). This substantially increases the difficulty of reaching the thermostat.

In my case, only my wife's petite hands could reach into the space.

Not a pleasant job...but, doable.

BTW...the pattern appears to be a deterioration of the thermostat seals (perhaps due to a corrosive coolant?).

[OSUCherokee]

Part of me thinks its just the engine not getting up to temp. I recently added the royal purple stuff to the coolant. Maybe it dropped temperatures too much? Also the engine generally seems to run cooler with an intercooler. Maybe it's just a combination of both?


Sent from my iPhone using AutoGuide.com Free App

[GS Stage 1]

Originally Posted by Jackknife In my case, only my wife's petite hands could reach into the space. Not a pleasant job...but, doable.

Must resist smart-ass comment....................

[Carbon Sky]

Originally Posted by Jackknife Some '06 Sols have an oil cooler attached to the back of the engine (mine does). This substantially increases the difficulty of reaching the thermostat. In my case, only my wife's petite hands could reach into the space. Not a pleasant job...but, doable. BTW...the pattern appears to be a deterioration of the thermostat seals (perhaps due to a corrosive coolant?).

Even without the oil cooler, it's a tight fit. Even though I was wearing puncture resistant nitrile gloves, my hands were pretty scratched and beat up from what is otherwise a relatively easy job if not for access.

As much as I trust Dexcool and continue to use it, I also don't run it to its recommended 5 year service life. Most associated Dexcool related issues seem somewhat related to old Dexcool (and often within the 5 year service life).

[Carbon Sky]

Originally Posted by OSUCherokee Part of me thinks its just the engine not getting up to temp. I recently added the royal purple stuff to the coolant. Maybe it dropped temperatures too much? Also the engine generally seems to run cooler with an intercooler. Maybe it's just a combination of both? Sent from my iPhone using AutoGuide.com Free App

I really wish people would stop adding additives to their coolant. But anyways that's a personal gripe.

There is no way any additive can drop temperature too much, sounds a lot more like classic symptoms of a failing/sticking t-stat.