When I last used my car on Friday evening there were no issues. I drove it to work this morning (about 12 miles, 20 minutes, mostly highway) and noticed the temperature gauge did not move at all from the cold mark. When I pulled in to the parking lot I then noticed the radiator fans were running full speed as well. Also, the engine block was barely warm to the touch. What could this be? A bad thermostat? This is my signature car, currently at 52,800 miles.
Temperature Gauge Stayed on Cold
- Thread starter RoGuE
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Might be a thermostat stuck open, but sounds like there is a CTS issue somewhere. This should be an easy diagnosis with a scantool. You know modern cars have ODBII on board diagnostics
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This forum isn't On Board.
Could be just low on coolant, and the temp sensor for the gauges is no longer in the fluid.
A scantool could be part of a thorough diagnosis, but it does not account for the possibility of a bad gauge, bad wiring to the gauge, or multiple ECTSs. An infrared thermometer will really get to the root cause of the issue quickly. One could also simply drive the car long enough to bring it up to temperature and check to see if the heater is functional, requiring no tools at all.
An engine block should be too hot to touch right after driving several miles. You can also check by turning the heat on, if the air is only slightly warm, the gauge wasn't lying.
The only thing that causes over-cooling is the thermostat stuck open.
The only thing that causes over-cooling is the thermostat stuck open.
Originally Posted By: ARCOgraphite
Might be a thermostat stuck open, but sounds like there is a CTS issue somewhere. This should be an easy diagnosis with a scantool. You know modern cars have ODBII on board diagnostics
This forum isn't On Board.
What is a CTS issue? I have a bluetooth scan tool. What would I look for? Trouble codes?
Originally Posted By: mightymousetech
Could be just low on coolant, and the temp sensor for the gauges is no longer in the fluid.
Coolant level looks good.
Might be a thermostat stuck open, but sounds like there is a CTS issue somewhere. This should be an easy diagnosis with a scantool. You know modern cars have ODBII on board diagnostics
This forum isn't On Board.
What is a CTS issue? I have a bluetooth scan tool. What would I look for? Trouble codes?
Originally Posted By: mightymousetech
Could be just low on coolant, and the temp sensor for the gauges is no longer in the fluid.
Coolant level looks good.
My thinking is the thermostat is stuck open. Fans are on as a fail safe mode to keep the car from over heating.
Nick1994
$100 site donor 2024
Bad coolant temp sensor
Plugged in my Bluetooth scan tool, shows fault code P0128 "
Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature)".
Could it still be the sensor? How do I check that?
Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature)".
Could it still be the sensor? How do I check that?
Originally Posted By: RoGuE
Plugged in my Bluetooth scan tool, shows fault code P0128 "
Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature)".
Could it still be the sensor? How do I check that?
I doubt it's your sensor, you did say the block is cooler than normal. If your coolant level is normal, I'd bet money the thermostat is stuck open and it is overcooling. The fault code is normal, the ECU expects the engine to reach operating temperature within some period of time, and if the thermostat is stuck open keeping the engine below that, it's telling you that it can't reach normal temperature.
The fans being on may be a failsafe in the off-chance the temperature sensor has actually failed; the ECU doesn't know why the coolant temperature is reporting low, so probably safer to command the fans on full in case the low temperature reported is in error.
Plugged in my Bluetooth scan tool, shows fault code P0128 "
Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature)".
Could it still be the sensor? How do I check that?
I doubt it's your sensor, you did say the block is cooler than normal. If your coolant level is normal, I'd bet money the thermostat is stuck open and it is overcooling. The fault code is normal, the ECU expects the engine to reach operating temperature within some period of time, and if the thermostat is stuck open keeping the engine below that, it's telling you that it can't reach normal temperature.
The fans being on may be a failsafe in the off-chance the temperature sensor has actually failed; the ECU doesn't know why the coolant temperature is reporting low, so probably safer to command the fans on full in case the low temperature reported is in error.
Nick1994
$100 site donor 2024
I once forgot to plug in my temp sensor on my Jeep. I started it and it put the electric fan on and set a CEL.
My guess is stuck open thermostat.
I have experience with this problem. Faulty thermostat fails to warm car up within a set time, and the computer does not know the cause, so it plays it safe and turns the fans on high until repaired. Your A/C will not work either. Replace the thermostat. It comes with a rubber seal around the perimeter. No gasket required, just a little coolant.
Seems the majority think it's the thermostat. I'll stop by a parts store on the way home. Should I go for OEM or is aftermarket okay?
Nick1994
$100 site donor 2024
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.
Then engine will warm up eventually, even if the thermostat is stuck open. It can't be colder than the ambient temperature.
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