Pressurization outflow valves

[Bhump]

Trying to find a leak in a 1973 pressurized skymaster for a friend. I am running pressure air thru front engine access with electric blower. In theory with master power off the outflow valves should be normally closed. However I have full air blowing out the outflow valve and backup outflow valve. Does this make sense?

[hharney]

It's standard Cessna so most Cessna shops that work on P models should be able to help you with that. Not sure if there's a process listed in the service manual, do you have the SM? Can send if you need one

[Ed A]

According to Tom Carr the outflow valves have to be blocked off.

See the attachment below.

[mshac]

Nice find, Ed!