Austin Ten Drivers Club

Just enquiring as to whether any members have seen a functional one of these things which seem to have been part of the equipment on later model radiators?
They look a lot like a ball check valve (possibly using a brass ball), judging by what's left on my car, but was the ball originally lightly spring loaded to keep it seated? I would be keen to make it functional if its at all possible.

Never seen one of these. Is it a fitting on the GRQ/GSI model?

It sounds as if it might be dispensible .

Peter: FRA series Goodwood (sorry, should've said in the original post). The radiator overflow pipe terminates at a banjo fitting on the top radiator tank close to the filler cap instead of being terminated as a standpipe inside the top tank. If you remove the banjo securing screw there's a spherical seating visible which connects to a drilling through the fitting into the top tank. Its mentioned in some of the literature as 'radiator now fitted with a steam valve'. I assume its to prevent the inevitable spit of coolant under heavy braking/on inclines etc with the possible extra of an early attempt at a pressurised cooling system. I've seen similar on other 30s/40s cars but never been in the position to pull one apart.
Bob: Definitely dispensable, this ones been gone for decades at least I'm hoping to try to bring it back to how it was in 1939 (and stop the spitting)

It may be a desperate remedy for a design fault . Something similar can happen to a traction engine going down a steep hill , when water can get carried over into the cylinder .

Rod
Interesting! It may be a safety device to reduce the risk of scalding when removing the rad cap prematurely. I remember in the Alps in my 10/4 in company with an overloaded Lichfield we stopped at the top of a pass to let the cars cool down (after being passed by a cyclist on the way up). My passenger loosened the bayonet rad cap and it flew up in the air on the pressure of the steam that was attempting to go down the overflow pipe
Peter W