Warning lamp / coolant gauge

[Andrew]

Hi all,
I have a 05 , 1.9d forte Multspace . Recently the Autodiagnosis warning lamp is coming on . Its intermittent .
Also in the last week the Coolant level is drifting up and down . From zero to whatever temp the engine is at . It just goes up and down
Any ideas ??

Thanks in advance

[ron]

Dodgy thermostat?cratch:

[homeruk]

Ideally you need to do a code read when the mil is on , that will give you a starting point