1927 Radiator Cap

[bpolson]

Is there any pressure in the system?    Let me know if I'm wrong.    The bottom of the cap seems to have a little spring to it - but it can't be much as it sits.   Not really a 'gasket' there.   I filled up the radiator (a couple inches from the top per my manual) and went for my first drive (10 miles).  It didn't leak out the cap at all.    Temp was good until I shut it off - but it bled coolant on my shop floor through the tube - perhaps a pint.    Looking for a 'sanity check' here and perhaps a good source for a proper fresh gasket.   Thanks.

   

[dibarlaw]

If it is an original style system with a honeycomb radiator core these are non pressurized systems. Just keep enough water in the top tank to cover the core. The top tank is then used as an expansion chamber as the fluid expands when heated. If the tank is slightly overfilled it has to go somewhere. Hence the overflow tube. I have made a cap gasket from neoprene and from leather the neoprene held up better.