My BMW 1997R Tourer has had numerous problems with overheating. The first time it went in for thermostat housing and new viscous fan, fine for 500 miles. Now temp gauge all over from normal into red and back and when I popped the bonnet, no leaks, just bit steam from coolant reservoir. Just ordered new water pump to be fitted this week, what else could be wrong with it if this does not cure it?

radiator... water pipes... blockage in flow of the water

The six pot bmw engine is a bitch to bleed properly I had the same problem with mine get a manual and read the section for bleeding the system.

I don't have the manual anymore so can't give you the step by step.

If its not airlocks I would get the engine cooling system pressure checked to see if there is a leak.

Also get a compression test done, you may be over pressurising the system if the head gasket is on its way out.