Problem with your 1991 318IS overheating after bleeding system?

I've experienced this and had it boil down to air pockets in the cooling system. My fix was to run the engine for 10-15 seconds, then squeeze the top radiator hose with the radiator cap off. This would cause a change in the level in the reservoir, and eventually work the air bubble out of where ever it was hiding. With the radiator cap off, you will eventually see a stream of fluid coming out just below the cap as you squeeze the top radiator hose.