hissing

Washed the bike last week gave her a quick lick of wax in anticipation of going out for a blast this weekend.....what a joke. Just about permanant rain in this neck of the woods. Anyway I now have probably the cleanest bike in Oxfordshire. Im a dangerous man with a tube of autosol and a bottle...

Just been checking the slave cylinder and when i pull the clutch lever in the slave cylinder hisses:dunno is this normal or is it time to order an MPL one or equivalent?? thanks