Charcoal Canister

[450slcguy]

1980 450SLC

I was toying around(painted) with my charcoal canister the other day and noticed that the bottom has what appears to be breather holes. Thinking that this should be a closed unit I blocked the intake port and applied vacuum to the other port. Appears to breath out the of bottom. There is a vacuum line from goes to the air sensor that sucks up fumes to burn them off. I smell no gas fumes when parked in the garage. The canister is in good shape(no visible rust), but I'm wondering why it would have a breather vent in the bottom of it.

My question is: Should the charcoal canister hold vacuum?

Thanks

[winecountryone]

As a smog tech in training I can say that most of the canisters of that vintage had a fresh air vent so that the stored vapors could be "purged" back into the intake and/or tank.
Electric valves were usually employed to open after the car is started drawing in fresh air and pushing the stored vapors out.
I do not have access right now to a model specific diagram but I'm certain the vent is supposed to be there.

[450slcguy]

Originally Posted by winecountryone

As a smog tech in training I can say that most of the canisters of that vintage had a fresh air vent so that the stored vapors could be "purged" back into the intake and/or tank.
Electric valves were usually employed to open after the car is started drawing in fresh air and pushing the stored vapors out.
I do not have access right now to a model specific diagram but I'm certain the vent is supposed to be there.

Thanks, one less thing to be concerned about.