Where is the coolant level sensor and how to fix or replace it on a Mercury Sable?? The coolant sensor is located in the coolant reservoir bottle. It cannot be serviced, you can only replace the reservoir. However, if just the sensor is bad, you can also try unplugging the sensor at the coolant reservoir bottle. Unscrew the two screws holding the reservoir bottle in place. With the bottle loose, tilt the bottle slightly toward you until you see wiring coming out of the reservoir bottle, that will be the wiring for the sensor plug. Unplug the sensor plug, and reattach the reservoir bottle. The Low Coolant light will not come on anymore, but you will now need to keep tabs on the antifreeze fluid level in the reservoir by occasionally checking the fluid level. One thing to consider when looking for an adhesive to fix this problem is the temp range the epoxy is rated for.