hey guys, X5 Overheating, need some help please

[Secrets]

It couldn't have been debris from the hose cause the fan rub off on the hose until there was a little hole where coolant would just be spraying under pressure(when at oper temp). No I didn't use rags to block any holes, I cleaned everything perfectly before installation. (not a messy diy, lol). The only thing I could think of right now us that aux pump. I'm not too sure what exactly is it's function and how it operates. What do you think?

[Secrets]

OK guys, I back with this problem again. I don't drive my X5 often that's why it took a little while to respond. I replaced the aux water pump and the problem went away for a while. The pump was faulty, it would work only when i shake it. I took it to almost 150mph twice and everything was ok. Here is the problem now, after driving for a few times, it's doing the same thing again, once i accelerate to over 80mph, the temp gauge will go up to red and right back to normal(half) the coolant will spill all over the left side of the engine from the expansion tank. It's a new(genuine) cap, expansion tank, radiator, fan, clutch, aux water pump, thermostat, water pump. Recently it sat there for about three weeks, and when I started it, I saw the left exhaust steaming out a bit, it lasted for about 20-30 seconds. Now i'm thinking I may have to replace the head gasket. No signs of coolant in the oil and or oil in the coolant yet. I've read a few posts concerning the oil seperator and its effects, I'm really not sure whether i should do the head job which I know will cost some good $$$ OR is there something else I can do. Any ideas will be greatly appreciated.