PSSSSSSSST Sound from Engine

[john2017]

Okay I know this may sound strange... but it is a real issue. 2017 3.5L ECO with 71K miles. No engine issues. Idle fine. After a modest acceleration when removing my foot off the gas pedal. There is a very distinct PSSSSSSST or Swishhhhhh sound... In my old days I was thinking vacuum sound. Any thoughts? Power brakes work fine. No pedal issue.
Again Thoughts?

 

[S20Workstation4]

The 3.5L Ecoboost is twin turbocharged. Heavy acceleration will activate the turbos. What you are most likely hearing is the Turbocharger blow-off valve, which relieves the pressure from the turbo after heavy-throttle usage.


- Joseph

 

[99WhiteC5Coupe]

Okay I know this may sound strange... but it is a real issue. 2017 3.5L ECO with 71K miles. No engine issues. Idle fine. After a modest acceleration when removing my foot off the gas pedal. There is a very distinct PSSSSSSST or Swishhhhhh sound... In my old days I was thinking vacuum sound. Any thoughts? Power brakes work fine. No pedal issue.
Again Thoughts?

Could this be the sound you are hearing: https://www.expeditionforum.com/threads/occasional-hooting-sound.53031/

 

[john2017]

Thanks Joseph. With your help and learning about the blow-off valve....The old Ford 390 FE series engine didn't come with a BOV..... problem solved. The recirculating output hose was disconnected! So the excess pressure was venting to the outside. Thanks again.