Further pondering on my radiator cap problem I reached the conclusion to eliminate this type of cap as they are not really designed for this application. The flat valveless caps were designed to be used low pressure overflow tanks and not pressurised systems like mine.
I have reverted back to a design I successfully used on my Marlin Sportster.
Revised Coolant design by
Sabrebuilder, on Flickr
The small bore coolant pipe now goes from a take off from the top radiator hose to the header tank. The BMW coolant sensor pipe had a spare port lending it to the new design. Unfortunately, it initially clashed with the oil filter casing so I had the move it to the right by 20mm. This meant sacrificing another new BMW top hose.
Revised Coolant design by
Sabrebuilder, on Flickr
I put a couple of rivnuts into intake manifold's webs to support the small hose clips.
Revised Coolant design by
Sabrebuilder, on Flickr
The 'flat' valveless radiator cap has now been swapped for a traditional 20 psi rad cap.
Revised Coolant design by
Sabrebuilder, on Flickr
I've also fitted the radio/heater part of the dashboard.
Heater/Radio fascia by
Sabrebuilder, on Flickr
The radio and heater controls will be fitted after the IVA test. For now there is a single switch that controls the heater control valve to switch the hot coolant going through the heater.
that's all for now..............
.........peter