Why do my check coolant level come on every day after I start-up

you have a air lock...Start the car with the radiator cap off. One of the easiest ways to bleed your car's radiator is to simply remove the radiator cap and then start your engine. Leave the vehicle running until it reaches its normal operating temperature. It may take between 15 or 20 minutes before your car generates enough heat to push out the air that has been trapped in your car's cooling system. You may find that you need to add additional coolant, as air pockets can artificially inflate coolant levels.
hope this helps

Check the Coolant (antifreeze) level. My 94 continental has a hard time shifting from 2nd to 3rd when the level is low. Also, this may indicate that the transmission fluid is too old to work properly. The transmission fluid is cooled at the bottom of the radiator, since cool fluid works better than hot fluid (especially when the trans fluid is old) that could make the transmission not shift properly. Keep the coolant level up until you can have the trans fluid checked.

You may be correct with what you think the problem may be, but another good thing to check is your coolant level. A low coolant level could cause false readings from you coolant temp sensor, which in turn will cause an engine hunting condition that you described.

add coolant let it run til the thermostat opens to see where the level is at if you need to add more or not

Low coolant

Check it when cold,not just
the overflow tank ,the remove the coolant
cap & check

May want to check the a/c housing drain also

start engine until get hot enough for coolant get hot pressurize then turn off engine check for leaking coolant hose.

Your engine does not overheat because the oil is low. Do you get heat out of the vents? Check the fluid level in the radiator not the reservoir. Due this with the engine cold. If the radiator is low than you have a leak somewhere. Add coolant to the radiator and see if you can see any abvious leaks. You may need to have the cooling system pressure checked in order to find the leak. If the coolant level is full in the radiator than you may have a bad thermostat. If you get heat out the vents than we can assume the coolant level is full and the water pump is working. When the temp gauge is hot feel the upper and lower hoses. If one is hot and one is cold than the t-stat may be the problem. If there is no heat out the vents and the coolant level is full than you may have a bad water pump. Let me know if you have any questions and I'll do my best to answer them. Thank you for using FixYa.com!

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No. It is not the thermostat. You are just low on coolant. The reason for the low coolant is either the fan is not working, the head gasket is blown, or the coolant system has a leak.
The fan is easy to check. When the temp comes up then the fan should come on.
The head gasket is easy to check also. Your oil will be milky white.
And if the radiator, radiator hose, or gasket leak can be harder to find.
The heater not working is because there is not enough water to heat the heater core.
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Thanks! Have a GREAT DAY!

coolant expands and contracts. in the morning the coolant is contracted and is not makeing contact with the sencer in the resevior tank. fist thing in the morning top off your tank to the full mark