Morrning Coolant light annoyance..... What is wrong?

I have a 1994 Ford Escort with 194k miles. for the last 4 or 5 mornings when I start the car the Check Coolant light comes on. I have checked the coolant and appear to have enough. After I have driven the car to work and shut it off I will restart the car and the light won’t come on. It only comes on first thing in the morning… Anyone know why? Please help.

The sensor for the coolant level is in your overflow reservoir. (From below the radiator cap, follow a black rubber hose to a plastic tank that has coolant in it).

When the car cools down the coolant contracts and gets sucked back into the radiator/cooling system, and the sensor goes dry and triggers the light. When you heat up the car, coolant expands and the overflow goes out the reservoir, and covers the sensor but the car doesn’t update the light until the next time you start it. Add coolant to the reservoir (as per manual instructions as to mix and type) and that will almost certainly fix the light.

It does, however, most likely mean that you have developed a small coolant leak, and it would be best to figure that out and fix it.

It is also possible that the sensor has gone bad - in which case you might try cleaning it, or just leave it alone, and unplug it to get rid of the light - BUT if you do unplug it you have to make sure to check the coolant level regularly so as not to overheat and wreck your engine.

This may be your coolant temperature sensor indicating that the coolant temperature is not rising quickly enough after a cold start. This could be due to a thermostat stuck parly or fully open. It could also be due to a faulty engine coolant temperature sensor. The Check Engine Light was illuminated as a result of a diagnostic trouble code being set. Take your car to a mechanic to have the code read and the exact cause diagnosed. The mechanic will likely suggest changing both the thermostat and the coolant temperature sensor because it is convenient to do both at the same time.

Actually, first verify that it is the “Check Coolant Light” (as OP noted) rather than the Check/Service Engine light. If it is the coolant light and you go to a mechanic you’ll spend a lot more than you need to in order to add a little coolant.

But I would take it to the mechanic to look for the source of the coolant leak.

I guess I stand corrected. I just read this on

There is a sensor in the coolant reservoir that tells you that the level is low. However, this sensor is famous for false warnings due to corrosion of the connectors or debris around the sensor bulb.
By the way: 194k on an old Escort. Good stuff.

I believe this sensor is reading a low level of coolant when cold in the morning, and turns the light on. This light will stay on until the engine is turned off, even if the coolant level rises due to the car heating up. Then, the coolant stays up enough during the day, until it cools off a bunch at night. Add a tad bit of coolant, like a 1/2 pint or pint in the morning, and see if the problem goes away.