Not sure. Maybe the cap just died but that looks quite spectacular or maybe there's something else not right with this pump? It still turns ok but I don't trust it.
Best part of £600 for a similar (2.0 bar) replacement.
Luckily I didn't rip out the other pump downstairs that feeds the old bathroom shower that's going soon! Some rejigging of the pipes on the hot water cylinder is needed here and once done means no more downstairs shower so I have to be sure the new one works properly.
Bloody bollxxxs!
I used to only buy Stewart Turner pumps...now I just throw in whatever is going cheap (salamander). I've lost count of the number of pump failures in the last 16 years!