Test for WP or thermostat broken.
Turn to max heat. Warm air out the vents = broken WP. Hot air most probably thermostat stuck on closed.
Change oil and filter. Check consistency of oil.
Do the el cheapo headgasket test.
Fill coolant to the brim on recovery tank (leave cap off). Remove all spark plug wires. Remove all but one spark plug and have someone crank the engine. If the coolant bubbles over, there is a leak from that portion of the engine (or cylinder). If not, go to the next cylinder, and then the next.... Note, it could be more than one area or more than one cylinder.
