You need to start this when it's cool not hot take your radiator cap off start the engine start adding water into the radiator keep checking it with your finger and keep adding when the water turns warm to the touch keep adding water if it's taking it and squeeze your upper radiator hose continuously to burp out the air keep adding water try that and see how it works
On some trucks it is mounted in the headliner above the driver's head. Looks like a round grille. Need to lower headliner to replace it, if that's where it is.
clean battery terminals first and retry if you are not getting any kind of power is a battery problem no a switch problem, what kind of vehicle is it ?
There are a lot of things to check. The idler is not the same as the tensioner, make sure they are both ok. The compressor could be experiencing lockups from contamination or ice build up / fluid entry due to charging or condenser problems. A used belt is a used belt, they stretch, even after 5 minutes. Make sure the belt size is correct.
It may just be the fuel pump seal at the top of the tank. it has to be dropped for a definite diagnosis. It is rare but the tank seams occasionally crack too. Good luck.
You need to run an OBD2 fault code test on this, it is the most important test you can do in order to make sense of what is going on. The test can be done by any Autozone parts store for free or other store like them.