Engine still overheats after number of repairs. Help!

Hi, I bought my car used with no known or visible mechanical problems. About 4 months after the purchase, the spot on the top of the radiator where the upper hose clamps onto it broke off. I drove it a little too much after that before I could fix it. Shortly after the engine started overheating and I noticed a crack in the radiator. It took a month or so before I could fix it, during which I drove it sparingly in town on a necessary basis only, no more than 3 miles at a time. I ordered a new radiator, then picked up new hoses and clamps, as well as changed the oil, oil filter and air filter and changed the radiator as well. Still was overheating. So I got a new thermostat and gasket seal, still overheating. Replaced the coolant temperature guage sensor, still overheating. Replaced the fan clutch today because I noticed the fan wasn't changing the speed as the engine temperature overheated. Still overheating.I've read several articles on bleeding the coolant system, but not sure if I'm doing it properly for my model car. I leave the radiator cap off and pour liquid as the engine reaches normal operating temperature. But it doesnt go down, at least not until I cut the engine off to prevent further overheating and let it cool down. Then when I come back out, it has gone down. I've checked with several mechanics, one at a bmw dealership, and a couple home ones, and they said if it was the coolant pump or cracked cylinder head (gasket), there would be fluid leaking, which there isn't. I'm at a loss, have been working on this car for awhile, trying to do it all myself. The possibility of a clogged engine is remote to me, but I know that is also a possibility. Any advice?