Isn't that a "zero-pressure" radiator? That honeycomb design core will start springing leaks if more than about 4 PSI is applied to it. The vent canister can be disassembled and cleaned by rolling the crimp back on the top and soldering it back together after a cleanup, assuming you can find a radiator repairman who still remembers how to solder.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!