2000 windstar 3.8L stalling when hot. Help me Please!

I have a 2000 ford windstar SEL 3.8l that is stalling after it warms up. It always turns over at first and runs great until the engine warms up. It then idles down until it stalls. It will not start back up unless I give it gas. It recently was doing this and I did a Intake Manifold & Valve Cover Repair putting these parts in'
Updated front valve cover
8 New intake isolator bolts with new seals
Upper intake manifold gasket set
Idle speed control motor gasket
Fuel pressure regulator vacuum line
Throttle body gasket
PCV Vacuum line
and replaced MAF, cleaned IAC.
After I did this the Van ran for a week and then started doing the same thing. I noticed that if I take the PCV Vacuum line off the intake it idles high but stays running. I noticed that my coolant level has slightly gone down and I suspect that there may be a leak but Im unsure at this point. Ive tried adjusting my throttle without success, and no MIL comes on, no codes present. I want to bring it to a shop but have had trouble finding a honest mechanic in my area. I would like any ideas of what can cause stalling like this, so Im more prepared and can have an educated guess as to what may be the issue. I really dont want to be taken to the cleaners by a dishonest or uneducated repair guy. Thanks

Just as a test, loosen the coolant cap a round. Then let us know if this affects the engine's performance.