the fan won't come on either because the fan motor or bearing has failed or the temp sensor that turns on the fan has failed, sometimes a fuse which indicate the motor is shortingor otherwise trying to draw too much amperage. If the fan isn't cooling yur car is overheating and that will boil the coolant out of your system and result in your constantly having to add coolant until the car overheats to such and extent that the head gsket blows or worse.

presumably we are referring to the expansion bottle, try fitting a new filler cap as a temp solution. we may have a stuck thermostat. though if fan isn't coming on? then these won't make any difference. have a garage check it out.can be anything from a blown fuse to failed motor on fan side.

costs are too variable to offer possibilities.

It sounds like you need to make it where the fans cut on first and then see if you have any problems.

yes

there is an obvious leak in the thing that you put water in and a little pipe that connects to it and its dripping onto another pipe that now has blue and brown rust on it. any ides on what to do or how much it would cost to get it fixed?