The water pump was siezed. When we disassembled it, we found out why. The end plate, a very complex aluminium casting, had suffered frost damage, causing the metal to foul the impeller.
Daimler made much use of cast aluminium. The pump body is one casting, the endplate another.
The impeller was not in bad condition, but the shaft had suffered scoring. It was metal-sprayed and re-machined to the correct profile.
The endplate, showing the frost crack. Note that the walls of the chamber are very thin, meaning that welding was impossible. The slot is the inlet for cool water from the bottom of the radiator. You can see the breather hole for lubrication of the bearing in the endplate.
There was no chance of getting a spare from the manufacturer, so we asked for help. Someone in the owner's club put us in touch with someone who took the task as a challenge. He examined the parts and spent three days figuring out what to do, then two days machining.
The end result was a perfect fit.