Allpar Forums banner

Coolant Temperature Signals ( Jeep Patriot 2.4 liter 4 cylinder )

463 Views 4 Replies 3 Participants Last post by  AllanC
Vehicle is 2016 Jeep Patriot with 2.4 liter 4 cylinder VVT engine and 6 speed Hyundai automatic transmission. Odometer is reading 97,000+ miles. Ambient air temperature is 76 deg F, overcast skys with lots of clouds and little direct sunlight, air conditioner in operation.

I noticed while driving and stopping that engine temperature slowly moved to 5/8 travel. In all the years of ownership temperature gauge has never behaved in this manner. It never goes over 1/2 mark between C and H. I am not sure if I have an issue or not. Scenario follows.

Left expressway and got caught in traffic snarl where it took 3 cycles of traffic light to clear intersection. So engine idling for about 8 minutes. I noticed that engine temperature gauge moved to 5/8 travel (beyond midpoint) because of long traffic wait. In all the years of ownership since 2017 the engine temperature gauge nevers goes over the 1/2 mark between C and H even on 100 deg F days with air conditioner operating.

After traffic cleared and able to resume normal forward speed engine temperature gauge returned to its midpoint of travel. Continued drive home and no further unusual temperature gauge situations.

After returning home I immediately connected scan tool to vehicle and monitored coolant temperature sensors. This engine has 2 sensors: one in head near #1 cylinder and one in coolant outlet / return hose to radiator. My Actron scan tool does not identify which specific sensor it is reporting. Due to several minutes of heat soak with engine off , both sensors were showing temperature of 230 deg F. Started engine and let it idle. Both sensors showed temperature dropping until one showed 210 deg F and other showing 208 deg F. Radiator fans were running on high speed. So that seems to indicate that the PCM is controlling and operating the radiator fans as designed and that is not the issue.

No recent cooling system work / maintenance that would involve opening, draining, replenishing system. Performed diagnostic self test on instrument cluster and gauge pointer moved according to test documentation. No engine diagnostic codes found in PCM. No coolant leaks. Fluid level consistent in overflow container.

Two questions:

1) Whch engine temperature sensor signal is sent to the instrument cluster for operating the gauge? Or maybe the PCM averages the 2 sensor signals and that is used?

2) Engine has two thermostats. I wonder if one is sticking and is sluggish to open until it gets beyond its design temperature and then suddenly opens?

Organism Terrestrial plant Adaptation Font Auto part
See less See more
1 - 5 of 5 Posts
I’d check some basics first;

Is the a/c condenser (and radiator) clean and not full of debris or bugs? Are there any radiator air baffles dislodged, torn or missing?
  • Like
Reactions: 1
. . . . Is the a/c condenser (and radiator) clean and not full of debris or bugs? Are there any radiator air baffles dislodged, torn or missing? . . . .
Vehicle was purchased from a dealership as used, program car with extended warranty in Oct 2017. At purchase time CarFax indicated no previous collision damage and upon inspection no missing parts in radiator grille area found. I have installed a fine mesh window screen wire over the condenser to prevent bugs and other debris from getting lodged in the fins. It is clear. A C condenser was cleaned before installing the bug screen so I am confident there is no unexpected air flow restriction through the condenser and radiator. No baffles or air flow directors in the radiator area. The front bumper fascia covers about 1/2 of the radiator / condenser area and that tends to keep bugs and other debris from collecting near the condenser.

Drove the vehicle today with ambient temperature of 84 deg F and in bright sunlight with air conditioner operating. Engine temperature gauge behaved as expected with consistent position at midpoint of travel. That corresponds to 210 deg F on the coolant temperature sensors as reported by scan tool. I stopped and checked and the dual radiator fans were running in low speed which seems to be correct. However I did not spend prolonged time idling engine in traffic.

I will have to observe and monitor as vehicle driven. I will have to duplicate a situation where there is a prolonged idle time, not moving in traffic, with heat load on engine and determine engine temperature gauge operation.
See less See more
  • Like
Reactions: 2
I don't see a 2nd coolant temp sensor. What are the wire colors?
The primary t/stat opens until the engine warms up some more. OAT requires a refractometer to measure antifreeze concentration.
The primary purpose of a cooling system is to maintain engine temperature in a range that will provide satisfactory engine performance and emission levels under all expected driving conditions. It also provides hot water (coolant) for heater performance and cooling for automatic transmission oil. It does this by transferring heat from engine metal to coolant, moving this heated coolant to the radiator, and then transferring this heat to the ambient air.

  • When the engine is cold and both the primary and secondary thermostats are closed. The coolant will circulate through the engine, heater system, and the bypass. The cooling system has no flow through the radiator
  • As the engine warms up, the primary thermostat will start to open at 77 °C (170 °F). Coolant will start to flow through the radiator and the internal transmission cooler. The primary thermostat will fully open at 95 °C (203 °F).
  • The secondary thermostat will start to open at 95 °C (203 °F). This will increase the coolant flow through the cylinder block and cylinder head and the radiator. The secondary thermostat will fully open at 104 °C (220 °F).
  • TURBOCHARGED ENGINE ONLY:the turbocharged engine has a single thermostat that starts to open at 90.5 °C (195 °F) and is fully open at 100 °C (212 °F). This is done to reduce resistance and increase flow.

Not exactly for a MK, but close to the guidelines.


See less See more
  • Like
Reactions: 1
. . . .I don't see a 2nd coolant temp sensor. What are the wire colors? . . . .
Engine head temperature sensor: violet; black / white

Coolant adapter return to radiator: blue; violet / pink

. . . . OAT requires a refractometer to measure antifreeze concentration. . . . .
Very interesting. Will have to research why one should NOT use a device with floating balls / floating bubble to measure freeze protection / concentration.

I found this documentation for radiator fan operation 2007 Chrysler Sebring with 2.4 liter 4 cylinder VVT engine. My Jeep seems to be following this scenario for fan operation. The Patriot has a series / parallel wiring arrangement to run fans at low or high speed.

See less See more
1 - 5 of 5 Posts