1993 Mitsubishi Mighty Max • 193,000 miles

Okay here goes it over heats I have change the thermostat 3 times now I have a 160 in it also change the water pump and the radiator cap it seam like it builds and air pocket and the antifreeze level seem to drop but it is not going any where that I can see I mean no leaks and I don't have any smoke out of the tail pipe. When it starts to over heat the air coming into the heater box blows cold as if I have no flow if I pop the cap it will start to flow again what can I do to fix the issue and I also notice I have to top it off too with more antifreeze and the overflow bottle do not fill up or go down after it cools it is a mighty max 2 wheel drive 5 spd 4 banger plus it also runs ruff at and idle like it has a miss.
December 2, 2012.

If you need to keep topping up coolant, there must be a leak somewhere. Minute leaks requires a pressure test to locate the source. Is the radiator cap of the correct rating?
You could have a bad head gasket and testing is required to confirm.

Dec 2, 2012.