Haven’t got my MK on the road yet ,so the amount of “Hot Running” has been limited but. When the engine is up to running temperature I get weeping from the overflow on the Micra radiator. Judging from the water staining quite a lot of water has come out whilst I have been running it with the bonnet in place.
My header tank is an unknown, small, round made of plastic ,possibly French with a
Plastic cap fitted.
I have a Micra pressure cap on the Rad. The question is am I over pressurizing the Rad? , Have I blown the head gasket?

The fan cuts in an goes off again so I don’t think its overheating
SVA coming up and I’m a bit concerned
Any ideas more then welcome

I amy be talking sh&te but you have a closed sytem when you have a header tank.

With radiator overflow tube, it either is left open or goes into a small overflow tank., This holds water and when it cools, the radiator cap opens to draw the water back in - discussion about how the caps work was posted in the last 2 weeks.

sounds like you have not got it plumbed in right ,we used the micra rad and the overflow was connected to the header tank on the scuttle and the bottom hose was teed in to the bottom of the header tank and we did awyay with the micra expansion tank.do a search there are plenty of diagrams showing r1 cooling circuit.

Couple of things you could do. You could route the overflow from the rad back to the header tank, or you could blank off the radiator overflow, replace the pressure cap on the radiator with a non pressurised cap and fit a pressurised cap to your header tank sufficient to run at the recommended pressure for your engine. We did the latter and haven't had any problems since.

Phil

Thanks for that