Why do i have to check it when i put my ear by the belt tensioner and the pulley was squeaking?
Ok - how’s this. If it is squeaking it needs to be replaced.
Of course, you still have a bigger problem - which is why the coolant is all brown and nasty.
The tensioner is squeaking because the pulley bearing is beginning to fail. You could replace just the pulley and bearing, but a complete tensioner would not be that much more and a better fix.
Coolant that is brown is not good at all. If it has been neglected, as in not changed for 5 years, this may be rust from the engine block. If it has been changed on time, there may be an internal engine problem.