Check your pee-hole!

[Orion]

It’s not really a major issue since, as your mechanic said, it’s only a telltale that the water pump is working ok. I’ve had my Honda blocked many times and just use a small steel wire inserted in the hole while the engine is running. Easily clears. It is the wasps. They like all small holes and several times have blocked the opening in my fire extinguisher! Not sure whether or not it would have enough pressure to work in an emergency or not, but best to keep it clear anyway.