C spanner will locate into the slot and allow it to be undone.
There will be a fine thread on the head nut and it will be murder tight.
If it was mine, working and not leaking I would leave it.
My local Pirtec do rebuild etc. for a good price
Pirtec.Good price
do you have something on him
I ended up getting some flexi’s made for a mains water booster pump, around £80 each. Glad I was billing my customer
Pirtec.Good price
do you have something on him
Pirtec.Good price
do you have something on him
They spell pirtek wrong, it should read pistake