[Davidbolam]

Originally Posted by flyerncle

The system is meant to run under pressure to hold the water against the cylinder walls otherwise the water will boil away from the hottest point's,cylinder walls and cyl head,so not having the cap on will allow it to boil.

Air will cause the same problem as there is no heat transfer to cool it.

Thanks

I think the best thing will be for me to take it our fun a spin this evening (with 10 jumpers on)

Ps have you been doing much flying lately? I went for a trip in a warrior the other week - stags shaw mast to Hexham the coast and back along the Tyne with my mate and son. Very very bumpy but good fun. It's gote thinking about selling the roadster to start a home build kit plane!