Ford Repair: 1996 Merc Mystique 6 cyl Cooling System, air bubbles, bleeder valve

Question
About 20 km into a drive home, my car began to overheat.  We stopped and let it cool down but only got about 20 km more before it overheated again.  We changed the thermostat, did a pressure test and looked for leaks.  There are no leaks but when we run the car, the coolant in the reservoir gurgles and bubbles.  There is no heat comming from the heater.  Could the water pump be the problem or possibly an air lock? Is there a bleeder valve on the cooling system? (We have ran it with the cap off in the driveway to purge the air)Any suggestions would be appreciated.

Answer
Well "No heat coming from the heater" sound like it could be a clogged heater core or air trapped inside.  Try to feel both heater hoses, they should both be warm.  Gurgling and bubbling coolant from the reservoir is normal when the engine is hot, as long as there are no air bubbles.  Make sure that the cap is holding pressure and there is good coolant flow through the radiator and the radiator is not clogged with debris.