Engine Temp Gauge Problem

[Bovina89]

2004 Jeep TJ ,2.4L engine, 5 spd trans, currently 108,000 miles. When I bought Jeep 2 years ago I noticed temp gauge needle stayed between 100 and 210. I drove vehicle (6000 miles in 2 years) and assumed it was bad thermostat. This week I decided to fix problem. I replaced 195 degree thermostat (tested old one and it was sat) and replaced coolant temp sensor. Ran Jeep idling for 20 minutes 1/2 mile down the road gauge temp did not change. Removed coolant temp sensor plug and measured 5vdc across pins which is correct. Compared resistance measurements of coolant temperature sensor with temp chart and all readings were sat. Verified coolant at coolant temp sensor.
The monitored Sensor resistance has never reached 860-970 ohms for a 194 degree temp according to chart. This makes me believe the thermostat is not reaching 195 degrees to open and the gauge is actually correct.
The heater blows hot air so I don't suspect air pocket (I refilled system per vendor manual). Jeep runs fine with no problems. Just don't want to drive until I have gauge/cooling problem corrected.
Thanks for replies and solutions,

 

[Jerry Bransford]

So you're saying the gauge never gets to 210, it always stays between 100 and 210?

Are you by any chance running thermostats labeled as "fail safe"?

 

[Chris]

What brand of replacement thermostat did you use? It's possible to end up with a faulty thermostat even if it is new.

 

[Bovina89]

So you're saying the gauge never gets to 210, it always stays between 100 and 210?

Are you by any chance running thermostats labeled as "fail safe"?

 

[Bovina89]

Today I disconnected plug to coolant temperature sensor and installed a 1000 ohm resistor across terminals. According to sensor resistance chart this should give approximate reading of 194 on temp gauge. It did. I now know the temp coolant sensor circuit is good and the gauge is accurate. Tomorrow I will remove the thermostat and evaluate from there. Thanks

 

[AjRagno]

I replaced 195 degree thermostat (tested old one and it was sat) and replaced coolant temp sensor. Ran Jeep idling for 20 minutes 1/2 mile down the road gauge temp did not change.

Before performing any further testing, disconnect the battery to clear the long term adaptive memory. It's likely that the PCM has not yet picked up that the sensor has been replaced.

I ran into the same issue recently. I believe that the PCM is currently estimating the engine temperature based on readings from other sensors. If you clear the PCM's memory, it will begin receiving and using information from the new sensor immediately.

View attachment 139905View attachment 139906

 

[Goatman]

What does "sat" mean?
And try what AJ said with the battery.

 

[Bovina89]

What does "sat" mean?
And try what AJ said with the battery.

What does "sat" mean?
And try what AJ said with the battery.

 

[Bovina89]

Sat means satisfactory. I ordered a new super stant thermostat and will test before installing. Will also verify engine water temps with temp gun. I will inform of findings. Thanks for all advice.

 

[Jerry Bransford]

Before performing any further testing, disconnect the battery to clear the long term adaptive memory. It's likely that the PCM has not yet picked up that the sensor has been replaced.

That's not an issue with the temperature sensor/sender.

 

[Bovina89]

Yesterday I installed super stant thermostat, bled system, installed coolant and drove jeep 10 miles. After approximately 3 miles I saw temp gauge needle begin to move. Needle was below mid scale dot between 100 and 210. I turned on AC and drove additional 6 miles. At end of trip needle was touching midscale dot. I will re-check coolant temp sensor and do additional temp verifications I have found no "smoking gun" yet. One thing I did notice was that radiator was replaced before I bought jeep in 2018. According to research the radiator is correct but also fits the 4.0 engine as well as my 2.4. Overcooling?

 

[chrisjohns38]

Yesterday I installed super stant thermostat, bled system, installed coolant and drove jeep 10 miles. After approximately 3 miles I saw temp gauge needle begin to move. Needle was below mid scale dot between 100 and 210. I turned on AC and drove additional 6 miles. At end of trip needle was touching midscale dot. I will re-check coolant temp sensor and do additional temp verifications I have found no "smoking gun" yet. One thing I did notice was that radiator was replaced before I bought jeep in 2018. According to research the radiator is correct but also fits the 4.0 engine as well as my 2.4. Overcooling?

Trying to wake this thread up. What ever happened? My gauges read like yours did after I purged the system of air. My coolant gauge reads approximately 140, 185, 210, 235, 250 when I do the diagnostic test on my 2001 4.0. Thanks.

 

[McPheeters]

Trying to wake this thread up. What ever happened? My gauges read like yours did after I purged the system of air. My coolant gauge reads approximately 140, 185, 210, 235, 250 when I do the diagnostic test on my 2001 4.0. Thanks.

I’m having the same issue did you figure anything out

 

[chrisjohns38]

I’m having the same issue did you figure anything out

Sorry for the delay.

Well, the good news is no problems at all with coolant temperature when monitored with an OBD code reader in "live data" mode.
The difference in present fixed (dummy) values is a mystery to me. I'm guessing its either a gauge voltage problem or the gauge cluster was changed out at some point with an aftermarket or USA versus Canada set point discrepancy with the OEM cluster. This is most likely, as the build sheet says it was shipped to Canadian specifications, including Km/Hr speedo.


Whatever, the Jeep handles extremely high local temperatures and poor operator skills without every burping, boiling, codes, smells, leaks, low of coolant, or high transient realtime values output to the code reader.

It is a Jeep after all.

My problem seems to have simply been improper bleeding of air from the system after a radiator replacement before I bought it.

 

[Stretch97]

Sorry for the delay.

Well, the good news is no problems at all with coolant temperature when monitored with an OBD code reader in "live data" mode.
The difference in present fixed (dummy) values is a mystery to me. I'm guessing its either a gauge voltage problem or the gauge cluster was changed out at some point with an aftermarket or USA versus Canada set point discrepancy with the OEM cluster. This is most likely, as the build sheet says it was shipped to Canadian specifications, including Km/Hr speedo.


Whatever, the Jeep handles extremely high local temperatures and poor operator skills without every burping, boiling, codes, smells, leaks, low of coolant, or high transient realtime values output to the code reader.

It is a Jeep after all.

My problem seems to have simply been improper bleeding of air from the system after a radiator replacement before I bought it.

I’ve been struggling with low engine temp for weeks now, I can’t seem to figure it out. I replaced the thermostat today with a stant superstat, yet I can’t seem to get up to temp while driving. At idle it gets up to temp fine.

I did some DMM testing, at 158 degrees in the ECT I got 1.8 K Ohms, which is in the right range from a table I found. The voltage, in pre ignition, was ~5 volts, which from what I’ve seen is correct.

Before I put the thermostat in I tested it in water and it looked alike it opened up at the right temp of 195. I’m just completely stuck as to what the issue is.

Do 2.4’s have two ECT sensors like the 4.0? Can the IAT sensor be a culprit??

 

[astjp2]

In plug and replug in the cluster, its just a stepper motor I believe

 

[Stretch97]

In plug and replug in the cluster, its just a stepper motor I believe

I’ll give that a try