I just picked up (saved) a 2006 4.2 s/c the front passenger side strut was hissing so I stripped it and took it out, it was a brand new part but looks aftermarket

When I plug up the air connection and squeeze the bag I hear a his from under the bearing mount, can this be remover so I can have a look?

I’ve arranged a second hand part to get me mobile again but just interested why a Brand new part has failed. 2014 L405 3.0d 150k miles
2006 L322 4.2 S/C 144k miles
Bateson Tilt bed 2004 23k miles

Youtube has strut dismantling videos. The seal at teh top is a 3 stack O ring but there is also an air hose withing the top housing from the connector to the inside of the bag to alow the strut to rotate. 2012 TDV8 Vogue (L322)

After much hammering i got the top mount off the strut and the pipe inside this to allow the steering to turn had broken where it attaches to the top of the strut.

Boiling water a bit Gorilla glue and a petrol pipe hose clio and all securely reattached to get the car mobile while i obtain another car for the spares im going to need to keep this one running 2014 L405 3.0d 150k miles
2006 L322 4.2 S/C 144k miles
Bateson Tilt bed 2004 23k miles