Temperature Gauge Stayed on Cold

[RoGuE]

Originally Posted By: Nick1994
Plug your scan tool in and take it for a drive. What is the temperature according to the scan tool?

Then engine will warm up eventually, even if the thermostat is stuck open. It can't be colder than the ambient temperature.


I'll check that on the way home after work.

Originally Posted By: SHOZ
Before you buy at the parts store open the hood and see if the upper hose is too hot to hold.


I forgot to mention I thought of that about 10 minutes after I shut it off this morning and it was warm, not too hot to hold. But it was 10 minutes later.

Originally Posted By: Linctex
The fans will also be on when the A/C system is on.

Engine "not hot" = stuck open thermostat


The A/C was off. It was in the 50s and raining, so I wouldn't expect the fan would be needed just after getting off the highway.

 

[bullwinkle]

Ford electric fans are a little weird in that they run at reduced speeds at idle, even on a cold start, then the PCM commands higher speeds for A/C or high engine temperatures. My guess is also a likely bad thermostat, I would stick to Motorcraft, or a Stant SuperStat, I've had good luck with both.

 

[RoGuE]

Originally Posted By: Nick1994
Plug your scan tool in and take it for a drive. What is the temperature according to the scan tool?

Then engine will warm up eventually, even if the thermostat is stuck open. It can't be colder than the ambient temperature.


I started it up and it idled for about 5 minutes while I messed around with some stuff in the torque app. The temp needle didn't budge from the cold mark. At this point the app showed it holding at 131F (outside temp is about 60 degrees). So I drove a mile to the highway, sat a minute at the light and then about 2 miles later the temp gauge shot straight up to the usual half mark. I pulled off my exit a few miles later and checked the temp in the app at a gas station and now it shows 194 degrees and holding. I got out and felt the upper rad hose and it was uncomfortable to hold but not very hot like it should be or has been. I drove another couple of miles to my house and by then the temp shows a little below the half mark and I check the app again and now it shows it holding around 175 degrees. The fans were not running constantly like they were this morning. Also the fault code has now cleared itself which makes sense. Was the thermostat stuck and it unstuck itself?

 

[SHOZ]

Most temp gauges are woefully inaccurate and don't start to lift off cold until around 140F. It sounds to me that 175F is too cold for a good t-stat and 194F is more like a US car.

 

[mk378]

When the engine is cold from being parked several hours, the OBD scan should show approximately ambient temperature. That would mean the sensor is OK, at least at that time. That is the only time you know the actual temperature of the engine, though you could get a guess by trying the heater.

Yes thermostats stick and unstick themselves. After 10 years, thermostat replacement is justified as a PM item. You could also replace the sensor while you have the system drained. I doubt it is very expensive.

 

[GMBoy]

You have a P0128 code. 95% of the time it is the Thermostat. I have fixed this issue a dozen times. Replace the thermostat.

 

[Merkava_4]

GMBoy --- Is it one of those electric thermostats with the electric solenoid to open and close it ?

 

[RoGuE]

Originally Posted By: GMBoy
You have a P0128 code. 95% of the time it is the Thermostat. I have fixed this issue a dozen times. Replace the thermostat.


Thanks for the confirmation. I'll go ahead and replace it this weekend. It seemed to be okay this morning. Should I go for the ACDelco or is a Carquest unit (old reviews say it is a Stant) from AAP okay?

 

[WobblyElvis]

The thermostat I put in my Malibu was a Stant and it was made in China. Not many parts made here anymore.

 

[daemontrym]

I have not had a chance yet because I have been working late.

 

[RoGuE]

I replaced the thermostat today. It has actually been working pretty well all week, but sometimes a little over 200 degrees. I replaced it with a Carquest unit. I found out after the fact that it is supposedly an "upgraded" thermostat according to this link (Post #4): http://www.yourcobalt.com/forums/problems-service/46977-thermostat-shopping.html

Also according to that link, my thermostat inner seal had failed just like the one in that photo which acts as a bypass. Drove it a few miles after replacement and no leaks, all is good so far. It had been 4 years and 25,000 miles since I last drained and filled the coolant so it was probably good to do it anyway.

Another thing, when I poured the coolant out from my drain pan, I ran it through a coffee filter since I saw a lot of sediment in my overflow tank (removed and cleaned it out the best I could). I'll include some of those photos.

Photos: https://imgur.com/a/uDjzD