astra oil presure switch

the oil pressure switch on my MKV Astra is leaking oil from around the grommet that sits on the probe that's connected to the wiring, I have replaced the switch previously due to this fault, but the grommet does not come with the switch, and I am unsure if the grommet is a oil seal or a retainer to keep the probe central, any ideas please

I'm sure these are screwed into the block, and come with a new sealing washer? If it is leaking from the electrical connection, its a dud - best replace it with a genuine Vauxhall part.
John

yeah! I checked with my local Vauxhall spares and was told there should be no pressure at the grommet, so the switch must be faulty, it was a motor factors part, so i will get a GM replacement, Thanks