Quite likely the plastic tubes from the tank are misrouted (assumes you have ruled out a stuck float).

 

Thanks. Tubes ok, float free. Now thinking there may be a small unnoticed leak. Although it’s a 98 only 20,000 on the clock.

 

A coolant leak would just cause the level to go down (and eventually trigger the warning light) and you would see it low when you open the header tank. After you have topped up the coolant, if the problem repeats (warning light comes on from time to time but you see good coolant level) and if the coolant level goes down after idling the engine for some time, this would mean that you may have a small cylinder head gasket leak which causes the combustion gasses to be pumped into the cooling system. Small head gasket leaks will keep the coolant level in the header tank high but the gas pockets will, from time to time, be purged into the header tank causing the coolant level to go down (and trigger the light). Then, more gasses will be pumped into the cooling system which will raise the coolant level in the header tank again and so on. Eventually, you will have to top-up the coolant again.

 

Found the clue to the coolant issue. A small amount of liquid on the engine behind the water pump. Just spitballing but would that probably be a thermostat housing problem that I have read about?

 

I have tried the following to get rid of this message:
1. Replace the tank with a new one. Still have the low coolant message.
2. Reversed the wire conection. Still have the low coolant message.
3. Unplugged the wire connection. Still have the low coolant message.
Is there any way to get rid of this message?

 

I have tried the following to get rid of this message:
1. Replace the tank with a new one. Still have the low coolant message.
2. Reversed the wire conection. Still have the low coolant message.
3. Unplugged the wire connection. Still have the low coolant message.
Is there any way to get rid of this message?

 

what about the level sensor?

 

The new tank had a new sensor, I am assuming that it works properly.
Could it be a disconnect somewhere in the wiring between the sensor and the computer that displays in the instrument panel?

 

BTW: the cap has to be screwed all the way down. I know from experience! Also, if the top hoses are reversed, (as shown below) you will have problems.