I filled the system up last summer was was good up until fall when it went warm again so I ignored it. I took off the high and low pressure port caps (in which the low pressure cap shot off across the other side of the garage). I checked it again yesterday with a set of gauges and was at 50psi, then left it over night and am sitting at 40psi.
This morning, my leak detector was squealing on the low pressure port. I've never actually had any leaks before, but I assume its possible that because the cap fired off like a rocket that the valve inside the port might be bad. Ive never had to replace one. Is this all that is needed?:
Or does it actually have to be something more expensive like:

thanks

 

After the system is evacuated, you can use the El Cheapo valve core remover for tires.