The coolant sensor in a Jeep tells you when the coolant in the radiator becomes too low to safely operate the vehicle. If this sensor fails to notify you via the dash panel light and an audible beeping sound, you may not know that the radiator has sprung a leak. This could leave you stranded by the side of the road, or worse, it could leave you with a few thousand dollars in engine repair bills. If you fear your Jeep's coolant sensor isn't working, there is one easy way to troubleshoot the problem.
Place a drain pan directly under the petcock on your radiator. The petcock is on the driver's side and at the bottom of the radiator.
Twist the petcock counterclockwise with a pair of pliers and drain 2 gallons of fluid into the drain pan. Close the petcock by turning it clockwise with the pliers.
Turn the Jeep on for a two minutes. The light should come on when the coolant levels in the radiator begin to fall. Draining 2 gallons should trigger the sensor, and the "Coolant" light should illuminate on the dash panel. If it does not, the sensor is defective. If it does, the sensor works.
Open the radiator cap on the top of the radiator and place a funnel into the hole. Drain the coolant back into the radiator.
