Hearing air escape after shutting off engine

[87ChevyR10]

Been hearing what sounds like air escaping after shutting off engine. AIR pump is disabled, so it isn't that. Could this be indicative of a valve not seating completely?

Thanks!

 

[smoothandlow84]

Brake booster leak?

 

[SkinnyG]

Not likely a cylinder bleeding off compression. I can't imagine a cylinder sealing that effectively on anything.

A/C vacuum bleeding out?

 

[bucket]

Inside the truck or outside? Is it after running the truck ewith the AC on?

If it's inside, most likely a vacuum line bleeding off (like the HVAC selector valve) or if it's outside after running the AC, it's just the AC system equalizing pressure.

 

[87ChevyR10]

Inside the truck or outside? Is it after running the truck ewith the AC on?

If it's inside, most likely a vacuum line bleeding off (like the HVAC selector valve) or if it's outside after running the AC, it's just the AC system equalizing pressure.

Outside truck. Doesn't matter if AC has been used or not (never heard any noise after use anyways). It's prolly a cracked vacuum line. I just recently pulled out a busted plastic line that connected the TBI to the charcoal can. Still can't believe how much better the MPG is after plugging that port on the TBI.

 

[smoothandlow84]

Since removing my emissions crap (air pump, exhaust manifolds)....maybe I shoulb plug the inlet from my charcoal canister and ditch that too? Better mpg is always a plus with a 5.7 liter.