VERY strange thing going on with my catch can!

[S3 Paul]

Erm... I posted recently about the lack of oil in my catch can...
well while jump starting a car today I decided to feel how much pressure was coming out of the outlet...
very little and almost a vacuume , this was at idle... Wrong?
my can is simple in place of the top hat and pipe into the tip.
i have fitted a bung to the tip.
Is something wrong?.

 

[s3dave]

Nope perfectly normal,, at idle your engine is in hg ..vacuum

 

[Dani_B19]

As dave says mate thats right. When did you have your engine rebuilt?