Open top of steam radiators

[Daniel Dodge]

On Saturdays inspection, I observed openings on the top of the radiators about 1/8" wide around the top half where the sections connect.

This is new to me.

[Bill Kibbel]

Could be that the water in the radiator froze - expanded.  That type of radiator doesn't have the threaded rods at the top.

It doesn't always result in a leak.  There are smaller diameter nipples inside those openings that insert into adjacent radiator sections.